For many people, measles belongs to a different era. It is remembered as a childhood illness involving fever, a distinctive red rash and several uncomfortable days at home. Yet behind those familiar symptoms lies one of the most contagious viruses known to medicine.
Up to nine out of ten people without immunity who have close contact with someone infected with measles can contract the disease. The virus can remain infectious in the air for as long as two hours after an infected person has left a room, making transmission possible even without direct physical contact.
The consequences can be far more serious than a temporary rash.
According to the World Health Organization's updated measles factsheet, published on July 15, 2026, approximately 95,000 people died from measles worldwide in 2024, the latest year for which the organisation has published comprehensive modelled mortality estimates. Most were children younger than five.
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Although vaccination has prevented tens of millions of deaths, outbreaks have continued to develop across several continents.
The Pan American Health Organization reported on October 9, 2026 that 55,792 confirmed measles cases and 77 deaths had been recorded across 17 countries and territories in the Americas between January 4 and October 3. That represented a 4.8-fold increase in cases compared with the corresponding period in 2025.
Meanwhile, the United States had already recorded more than 4,400 confirmed infections by mid-October, and European health authorities continued monitoring clusters and outbreaks in multiple countries.
The resurgence raises important questions about how measles spreads, who faces the greatest danger and why an infection that usually resolves within weeks can sometimes have consequences lasting a lifetime.
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What exactly is measles, and what causes it?
Measles, also known as rubeola, is a highly contagious viral infection caused by the measles virus, a member of the genus Morbillivirus within the Paramyxoviridae family.
The virus primarily enters through the respiratory tract, where it infects susceptible cells before spreading through the body's immune and lymphatic systems. As the infection progresses, it can affect multiple organs, producing the characteristic combination of fever, respiratory symptoms and a widespread skin rash.
Humans are the only natural reservoir for the measles virus. Unlike diseases such as Ebola or certain forms of influenza, measles does not depend on an animal population to maintain transmission.
This distinction is significant because it means the virus could theoretically be eliminated worldwide through sufficiently widespread and sustained vaccination.
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Before measles vaccines became available in 1963, major epidemics occurred approximately every two to three years. WHO estimates that measles caused roughly 2.6 million deaths annually during the period before widespread vaccination.
Routine childhood immunisation subsequently transformed the disease's impact, but the virus continues to circulate wherever enough people remain susceptible.
How do people become infected with measles?
Measles spreads through infectious particles released into the air when someone carrying the virus breathes, talks, coughs or sneezes.
When these particles are inhaled by another person, they can enter the respiratory tract and initiate infection. Unlike diseases that require contaminated food, sexual contact or exposure to blood, measles can spread simply through sharing indoor air with an infectious individual.
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According to the US Centers for Disease Control and Prevention's clinical overview, updated in August 2026, the measles virus can remain infectious in the air for up to two hours after the infected person has left the area.
This means exposure can occur in environments such as classrooms, waiting rooms, airports, public transport and other enclosed spaces where an infected individual has recently been present.
The disease does not require prolonged face-to-face contact. A susceptible person may inhale infectious particles without knowing that someone with measles was previously nearby.
Although contaminated surfaces may also play a role in transmission, airborne spread is the principal concern.
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Why is measles so much more contagious than many other infections?
Measles is exceptionally efficient at spreading between people who have no immunity. The CDC estimates that up to 90% of susceptible individuals exposed through close contact with someone who has measles will become infected.
Epidemiologists often describe this transmissibility using the basic reproduction number, known as R0. This represents the average number of secondary infections caused by one infected individual in a population where everyone is susceptible and no preventive measures are taken.
For measles, traditional estimates of R0 commonly range from 12 to 18, although actual transmission depends on population characteristics and environmental conditions.
That means a single infection introduced into an unprotected community can rapidly generate numerous additional cases.
The danger is particularly pronounced in schools, nurseries, residential facilities and other environments where many susceptible individuals spend time close together.
High vaccination coverage is therefore essential. Unlike some less contagious infections, measles can spread even when a relatively small proportion of the population remains unprotected.
Can someone spread measles before developing a rash?
Yes. One of the most challenging characteristics of measles is that infected people can become contagious before the disease's most recognisable symptom appears.
According to the National Foundation for Infectious Diseases' updated measles guidance, people with measles can transmit the virus from approximately four days before the rash develops until four days after its appearance.
During the early infectious period, a patient may experience only a fever, cough, runny nose or irritated eyes. These symptoms can easily be mistaken for a common respiratory infection.
Someone may therefore attend school, go to work or visit a healthcare facility without realising they have measles.
This creates opportunities for transmission before health authorities can identify the infection and begin tracing contacts.
The combination of airborne spread, high contagiousness and transmission before the characteristic rash appears makes measles particularly difficult to contain once it enters an under-vaccinated community.
What are the first symptoms of measles?
The first symptoms generally develop seven to 14 days after exposure, although the precise incubation period can vary.
The illness frequently begins with a high fever, sometimes exceeding 40°C, accompanied by coughing, a runny nose and red, watery eyes. Patients may also experience fatigue, reduced appetite and general weakness.
The combination of coughing, coryza, meaning nasal inflammation and discharge, and conjunctivitis, meaning inflammation of the eyes, is sometimes described medically as the three Cs of measles.
According to the WHO's explanation of measles symptoms, these early symptoms often last several days before the characteristic rash develops.
Another distinctive sign is the appearance of Koplik spots, small white or bluish-white lesions that can develop inside the mouth, particularly on the inner surfaces of the cheeks.
These spots often appear before the skin rash and can help doctors recognise the infection.
However, not every patient develops easily identifiable Koplik spots, and the early symptoms are similar to those caused by several other viral illnesses.
What does the measles rash look like?
The measles rash typically appears approximately 14 days after exposure, often three to five days after the first symptoms begin.
It usually starts around the face and hairline before spreading down the neck, chest, abdomen, arms and legs. The rash consists of flat and slightly raised spots that may merge into larger areas as the infection progresses.
On lighter skin, the spots often appear red or reddish-brown. On darker skin, the colour can be less obvious, making other symptoms and the pattern of the rash particularly important during clinical assessment.
The rash generally lasts several days before gradually fading, often following approximately the same progression in which it appeared.
Some patients experience their highest fever around the time the rash develops, while others begin improving shortly afterwards.
However, the appearance or disappearance of the rash does not reliably indicate whether serious complications are developing.
A further challenge is that some severely immunocompromised patients may develop measles without a typical rash, making diagnosis more difficult.
What happens inside the body during a measles infection?
After entering the respiratory system, measles virus can infect immune cells and spread through the lymphatic system into the bloodstream.
This allows the virus to reach different tissues and organs, producing a systemic infection rather than an illness confined to the nose and throat.
The immune system eventually recognises and attacks infected cells, contributing to the fever, inflammation and characteristic rash associated with measles.
In most otherwise healthy people, this immune response eliminates the infection and produces long-lasting protection against future measles infections.
However, the process can also cause substantial inflammation and temporary disruption of normal immune function.
The virus may damage respiratory tissues, increasing vulnerability to pneumonia and other complications. In severe cases, infection and inflammation can affect the brain, producing potentially life-threatening neurological symptoms.
The immune-system effects are particularly concerning because they can continue influencing a patient's health after the original symptoms have disappeared.
Measles can weaken the body's protection against other diseases
One of the most surprising discoveries about measles is that the virus can interfere with immune memory.
The immune system normally remembers infections and vaccinations it has encountered in the past. This allows the body to recognise familiar pathogens and respond more effectively when they appear again.
Measles can disrupt this protection by infecting and damaging certain immune cells involved in maintaining immune memory.
This phenomenon is known as immune amnesia.
According to the CDC's clinical explanation of measles complications, immune amnesia can leave patients more vulnerable to other infections for months or even years after recovering from measles.
Research suggests that the virus can reduce existing populations of memory immune cells, potentially weakening protection against pathogens that the body had previously encountered.
The extent and duration of this effect vary, and not every patient develops severe long-term immune problems.
Nevertheless, the findings help explain why measles can create health risks extending beyond the fever and rash traditionally associated with the disease.
Why can measles cause severe pneumonia?
Pneumonia is among the most important complications of measles and one of the principal causes of measles-related deaths.
The virus can directly cause inflammation within the lungs, interfering with normal breathing and oxygen exchange. It can also weaken the immune system, increasing susceptibility to secondary bacterial infections that may produce additional lung damage.
According to the National Foundation for Infectious Diseases, approximately one in 20 children who develop measles experience pneumonia.
Symptoms can include worsening coughing, rapid breathing, chest discomfort, unusual tiredness and difficulty obtaining sufficient oxygen.
Young children may show signs such as rapid or laboured breathing, poor feeding or difficulty remaining alert.
Severe pneumonia can require hospital admission, supplemental oxygen and, in some cases, intensive respiratory support.
The risk is particularly serious for children with malnutrition, underlying respiratory conditions or limited access to medical treatment.
Can measles cause permanent brain damage?
Although neurological complications are considerably less common than respiratory symptoms, they represent some of the most serious consequences of measles.
One complication is acute encephalitis, an inflammatory condition affecting the brain. It can develop during or shortly after the measles infection and may cause seizures, severe headaches, confusion or changes in consciousness.
According to the CDC's assessment of measles complications, approximately one in every 1,000 measles cases develops acute encephalitis.
The condition can cause permanent neurological damage, including difficulties with movement, cognition, hearing or other functions. In the most severe cases, encephalitis can be fatal.
Other neurological complications may involve inflammation of the brain or spinal cord triggered by the body's immune response.
These complications are rare compared with uncomplicated measles infections, but they demonstrate why the disease cannot safely be dismissed as a harmless childhood illness.
A rare brain disease can appear years after recovery
One of the most disturbing complications associated with measles is subacute sclerosing panencephalitis, commonly abbreviated SSPE.
Unlike acute encephalitis, which develops around the time of infection, SSPE may not appear until several years after the patient seems to have recovered completely.
The disease occurs when measles virus persists in the nervous system and gradually causes progressive brain damage.
Early symptoms may include behavioural changes, difficulties at school, memory problems or changes in personality. As the condition progresses, patients can develop involuntary muscle movements, seizures, severe neurological impairment and eventually loss of essential bodily functions.
According to the US National Institute of Neurological Disorders and Stroke, SSPE is a rare but almost invariably fatal disorder.
The condition most commonly becomes apparent several years after the original infection, often approximately seven to ten years later.
Children infected with measles at a very young age face a particularly elevated risk of developing SSPE.
Although the complication affects only a small minority of infected individuals, its consequences are devastating. It also illustrates that recovering from the initial symptoms does not always eliminate every possible long-term consequence of measles.
Who is most likely to become infected with measles?
Anyone without adequate immunity can contract measles, regardless of age, sex, ethnicity or general physical fitness.
However, exposure risk is influenced by vaccination status, contact with infected individuals and the level of transmission within the surrounding community.
People who have never received a measles vaccine and have never previously had the infection are particularly vulnerable.
Young children who have not yet completed their vaccination schedules also face increased exposure risks during outbreaks.
Healthcare workers, international travellers, schoolchildren and people living in communities with low vaccination coverage may encounter additional opportunities for exposure.
The WHO's July 2026 factsheet identifies unvaccinated individuals as the population most vulnerable to infection.
However, infection and severe illness are not the same outcome. A healthy unvaccinated adult and an unvaccinated infant may both be susceptible, but their risks of complications can differ substantially.
Which groups face the greatest risk of severe measles?
The likelihood of serious complications is particularly high among infants, young children, adults and people with weakened immune systems.
According to the CDC's clinical guidance, children younger than five, adults older than 20, pregnant women and immunocompromised individuals are among those at increased risk.
Children with malnutrition, particularly vitamin A deficiency, may experience more severe illness because their bodies are less able to withstand the infection and its complications.
People receiving chemotherapy, organ transplant recipients and individuals with serious immune-system disorders may also face considerable risks.
Patients living with advanced or poorly controlled HIV can be especially vulnerable because their immune systems may already be compromised.
Healthcare access is another important factor. A child who develops measles-related pneumonia in a well-equipped hospital may have a very different prognosis from a child living in an area where oxygen, antibiotics or emergency treatment are difficult to obtain.
This helps explain why measles fatality rates differ substantially between countries.
Why are babies especially vulnerable to measles?
Infants represent one of the most vulnerable groups because many have not yet reached the age at which routine measles vaccination is administered.
Newborn babies may initially receive some protection through antibodies transferred from their mothers during pregnancy.
However, this protection declines over time, and the duration varies according to maternal immunity and other factors.
In many countries, the first routine measles vaccine dose is administered around the first birthday. This creates a period during which some infants may have declining maternal antibodies but have not yet received their first routine vaccination.
Young babies can also experience severe complications because their immune systems are still developing, and respiratory illness or dehydration can become dangerous more quickly.
During outbreaks, health authorities may recommend an additional early vaccine dose for infants aged six to 11 months.
This early dose does not normally replace the two-dose routine vaccination schedule that begins after the first birthday.
Can adults become seriously ill from measles?
Although measles is often associated with childhood, adults can also develop severe disease.
Older adolescents and adults without immunity may experience high fever, severe fatigue, pneumonia and other complications requiring medical treatment.
The WHO identifies adults older than 30 as a group in which complications are more common, while CDC guidance recognises increased complication risk among adults older than 20.
The precise risk varies with overall health and immune status, but adulthood does not provide natural protection against the virus.
Some adults may also have uncertain vaccination histories, particularly if they grew up during periods when immunisation schedules differed or vaccination coverage was incomplete.
People who are unsure whether they have received appropriate vaccination should consult a healthcare professional, particularly before international travel or during a local outbreak.
Why is measles particularly dangerous during pregnancy?
Measles during pregnancy can create serious risks for both the pregnant patient and the developing baby.
Pregnant women who are not immune may experience severe respiratory complications, including pneumonia, and can require hospital treatment.
According to the CDC's clinical overview of measles during pregnancy, infection is associated with an increased risk of pregnancy loss, premature delivery and babies being born with low birth weight.
In rare circumstances, measles can also be transmitted to the fetus, resulting in congenital measles.
The measles, mumps and rubella vaccine is a live-attenuated vaccine and is generally contraindicated during pregnancy. People planning pregnancy should therefore discuss their vaccination status beforehand.
Pregnant individuals who have been exposed to measles and are not immune require urgent medical assessment because protective immunoglobulin treatment may be recommended.
Which countries are most affected by measles?
Measles occurs worldwide, but transmission is especially persistent in countries where vaccination coverage is incomplete or healthcare systems struggle to reach all children.
Historically, substantial disease burdens have occurred in parts of sub-Saharan Africa, South Asia and the Middle East.
However, recent years have demonstrated that measles outbreaks are not confined to lower-income countries.
According to the WHO's global measles report published in November 2025, an estimated 11 million measles infections occurred worldwide in 2024, approximately 800,000 more than in 2019.
The report highlighted increases in infections across the Eastern Mediterranean, European and South-East Asian regions compared with 2019.
These geographical patterns are influenced by several factors, including childhood vaccination coverage, population movement, healthcare access and local outbreaks.
Countries experiencing armed conflict, displacement or major disruptions to routine vaccination services are particularly vulnerable.
Measles outbreaks are affecting countries across Africa
Africa continues to carry a substantial burden of measles, particularly in communities where routine vaccination and healthcare access remain insufficient.
According to the European Centre for Disease Prevention and Control's October 9, 2026 surveillance report, African public health authorities reported large numbers of suspected infections in the Democratic Republic of the Congo, Somalia and Burkina Faso during 2026.
The report cited Africa CDC figures showing more than 173,000 suspected cases and 1,718 deaths across 23 African Union member states as of September 20, although confirmed and suspected cases were recorded separately and surveillance completeness varied.
The Democratic Republic of the Congo accounted for a particularly substantial share of reported infections and deaths.
Countries such as Burundi, Mali and Togo also experienced measles activity, prompting additional monitoring and public health responses.
Outbreak control can be complicated by difficult transport conditions, shortages of healthcare workers and interrupted vaccination programmes.
When children are displaced by conflict or natural disasters, crowded living conditions can also create environments where a highly contagious virus spreads rapidly.
Bangladesh experienced a major measles emergency in 2026
One of the most serious measles outbreaks of 2026 developed in Bangladesh, where infections spread across much of the country.
In an April 23 outbreak report, WHO described a rapid increase in infections affecting 58 of Bangladesh's 64 districts.
Children younger than five accounted for approximately 79% of the reported cases at that stage, while children younger than two represented a substantial proportion of infections.
The situation continued to deteriorate in the following months.
According to the ECDC's October 9 surveillance report, Bangladeshi health authorities had recorded approximately 201,625 suspected measles cases, including 22,116 laboratory-confirmed cases, by early October 2026.
Authorities also reported 1,040 suspected or confirmed measles-related deaths. These are provisional outbreak figures, and the suspected deaths should not be treated as laboratory-confirmed measles fatalities.
The emergency led to vaccination campaigns, expanded surveillance and measures intended to identify infected children earlier.
It also demonstrated how large outbreaks can develop when gaps remain in vaccination coverage, even in countries with established immunisation programmes.
Measles has returned across the Americas
The Americas are experiencing a substantial resurgence of measles following years of progress towards regional elimination.
According to the Pan American Health Organization's October 9, 2026 epidemiological update, 55,792 confirmed cases and 77 deaths had been reported across 17 countries and territories between January 4 and October 3.
The number of reported infections was approximately 4.8 times higher than during the corresponding period of 2025.
Guatemala recorded the largest number of confirmed cases, followed by Mexico, the United States, Peru and Canada. Together, these five countries accounted for approximately 99.5% of confirmed infections in the region.
Cases were also identified in countries including Bolivia, Brazil, Colombia, Argentina and several Central American states.
The organisation classified the regional public health risk as very high, citing vaccination gaps, continuing outbreaks and the possibility of further transmission through international travel and large gatherings.
However, a very high regional public health risk does not mean every vaccinated individual faces a high personal risk of infection.
Measles cases in the United States have reached their highest level in decades
The resurgence is particularly visible in the United States, where measles was declared eliminated in 2000 after sustained domestic transmission had been interrupted.
That designation did not mean that imported infections could no longer occur. People infected abroad could still introduce the virus, particularly into communities where vaccination coverage was insufficient.
According to the CDC's October 16, 2026 surveillance update, the United States had recorded 4,410 confirmed measles cases by October 15.
The figures included 42 newly reported outbreaks during 2026, with approximately 96% of confirmed infections associated with outbreaks.
By comparison, the country recorded 2,289 confirmed cases during the whole of 2025 and just 285 during 2024.
The 2026 figures represented the highest annual case total reported since the United States achieved measles elimination in 2000.
Large numbers of infections have been concentrated in communities where many people lack documented vaccine protection.
The situation illustrates how quickly measles can return when vaccination gaps allow sustained transmission, even in countries with advanced healthcare systems.
Is measles also spreading in Europe?
Yes. Measles continues to circulate in parts of Europe despite widespread childhood vaccination programmes.
According to the ECDC's latest monthly measles surveillance report, 2,335 cases were reported across 30 EU and European Economic Area countries during the 12 months ending August 31, 2026.
Italy recorded the highest total, with 653 cases, followed by Bulgaria with 564, Romania with 255, Spain with 230 and France with 146.
Children younger than five accounted for approximately 27% of reported infections, while more than half of the cases occurred among people aged 15 or older.
Among patients whose age and vaccination status were known, approximately 72% were unvaccinated.
The ECDC recorded no deaths attributed to measles in its routine EU/EEA surveillance during that particular 12-month period, although serious outcomes and outbreaks continued elsewhere in the wider European region.
In a separate October 9 report, the agency noted that England had recorded 1,003 laboratory-confirmed cases during 2026 through September 7.
The findings demonstrate that measles remains a concern beyond countries where it has historically been widespread, particularly when local vaccination gaps allow imported infections to spread.
Why are measles outbreaks increasing again?
One of the most important explanations is insufficient vaccination coverage.
Measles is so contagious that approximately 95% of a community generally needs protection through two-dose vaccination to reliably prevent sustained transmission.
When vaccination coverage falls below that threshold, the number of susceptible individuals can gradually increase.
The WHO and UNICEF's global vaccination estimates released in July 2026 showed that only 84% of children worldwide received their first measles vaccine dose in 2025.
Just 77% received a second dose.
These figures remain substantially below the coverage required to prevent outbreaks. WHO and UNICEF also reported that 57 countries experienced large or disruptive measles outbreaks during 2025.
Several factors contribute to these gaps. In some countries, armed conflict, displacement, poverty and understaffed healthcare systems prevent children from receiving routine vaccines.
Elsewhere, vaccination programmes have struggled to recover fully from disruptions experienced during the COVID-19 pandemic.
Misinformation and vaccine hesitancy can also reduce uptake in communities where vaccination is readily available.
Even when a country has high national vaccination coverage, smaller communities with much lower uptake can remain vulnerable to outbreaks.
How deadly is measles?
Measles can be fatal, but the probability of death varies substantially between countries and patient populations.
According to WHO, approximately 95,000 people died from measles globally in 2024. Most of those deaths occurred among children younger than five, particularly in countries with limited access to healthcare.
In the United States, the CDC estimates that approximately one to three out of every 1,000 children infected with measles die from respiratory or neurological complications.
That corresponds to a fatality risk of approximately 0.1% to 0.3% among infected children in the US context.
The risk can be considerably higher in environments where malnutrition, vitamin A deficiency or inadequate healthcare complicate treatment.
The global burden is also influenced by the number of infections. Even when a disease has a relatively low fatality risk in an individual patient, millions of infections can result in large numbers of deaths.
This explains why measles continues to cause substantial mortality despite the existence of a highly effective vaccine.
How many people require hospital treatment?
Hospitalisation is an important indicator of measles severity because complications can develop even in people who were previously healthy.
According to the National Foundation for Infectious Diseases, approximately one in five unvaccinated people in the United States who develop measles require hospital treatment.
The likelihood of admission is particularly high among young children, although adults and immunocompromised patients may also require intensive medical care.
Common reasons for hospitalisation include dehydration, pneumonia, severe respiratory symptoms and complications affecting the nervous system.
However, hospitalisation figures vary between outbreaks. They depend on patient age, vaccination history, case detection practices, clinical severity and local admission policies.
The one-in-five estimate should therefore not be interpreted as a universal hospitalisation rate for every measles outbreak worldwide.
How do doctors diagnose measles?
Although measles has recognisable clinical features, symptoms alone cannot always establish a diagnosis.
Fever, respiratory symptoms and skin rashes can occur with several other infectious diseases, including rubella, certain viral respiratory infections and other illnesses that produce widespread inflammation.
Doctors therefore consider the timing of symptoms, recent travel, vaccination history and possible exposure to a confirmed measles case.
Laboratory testing can detect measles-specific antibodies in blood samples or identify the virus's genetic material through molecular testing.
According to the CDC's clinical testing recommendations, suspected cases should generally be assessed using appropriate blood and respiratory samples.
Because measles is so contagious, people with suspected infection should contact healthcare services before visiting a clinic or hospital whenever possible.
This allows staff to arrange appropriate isolation and avoid exposing vulnerable patients in waiting areas.
Is there a cure for measles?
There is currently no specific antiviral medicine routinely approved to cure measles.
Treatment primarily focuses on relieving symptoms, maintaining hydration and preventing or managing complications while the immune system clears the infection.
For uncomplicated illness, patients may receive advice on rest, fluid intake and appropriate fever-relieving medication.
Severe cases can require hospital treatment, particularly when patients develop pneumonia, dehydration or neurological complications.
According to the CDC's updated measles clinical guidance, healthcare professionals should promptly assess and treat complications such as pneumonia and secondary bacterial infections.
Antibiotics do not treat the measles virus itself. However, they may be necessary if a patient develops a bacterial infection alongside measles.
Patients with serious respiratory complications may require supplemental oxygen or intensive care, while severe neurological symptoms demand urgent specialist assessment.
The absence of a specific cure makes prevention particularly important, especially for people at increased risk of complications.
Can vitamin A treat or prevent measles?
Vitamin A has an established role in the supportive treatment of certain children with measles, particularly those who are hospitalised or at increased risk of severe complications.
The vitamin plays an important role in immune function, vision and the maintenance of healthy tissues. Vitamin A deficiency can worsen the consequences of measles, especially among malnourished children.
According to the CDC's August 2026 clinical recommendations, vitamin A may be administered to infants and children with measles under medical supervision as part of supportive care.
However, vitamin A is not an antiviral medicine and does not cure measles. It also cannot replace vaccination or reliably prevent infection.
Excessive vitamin A intake can be toxic and may cause liver damage, neurological symptoms and other serious complications.
Pregnant women should be particularly cautious because high doses of vitamin A can harm fetal development.
For these reasons, high-dose vitamin A should not be administered independently in an attempt to prevent or treat measles.
How effective is the measles vaccine?
Vaccination provides the most reliable protection against measles and its potentially serious complications.
The measles vaccine is commonly administered as part of the MMR vaccine, which also protects against mumps and rubella.
In some countries, children may receive the MMRV vaccine, which additionally protects against varicella, commonly known as chickenpox.
According to the CDC's measles vaccination guidance, one dose of the MMR vaccine is approximately 93% effective at preventing measles.
Two doses increase protection to approximately 97%.
These figures mean vaccination substantially reduces the likelihood of infection, although no vaccine provides absolute protection to every individual.
People who develop measles despite being vaccinated are generally more likely to experience a milder illness and are less likely to transmit the virus than people without existing immunity.
Most people who respond appropriately to the full vaccination series maintain long-lasting protection.
When should children receive the measles vaccine?
Vaccination schedules differ between countries, but most routine programmes recommend two doses during childhood.
In the United States, the CDC recommends the first MMR dose between 12 and 15 months of age and the second between four and six years.
Other countries may administer the first dose earlier or provide the second dose at a different age, depending on national immunisation policies and local disease risk.
During outbreaks or before international travel, infants aged six to 11 months may be advised to receive an additional early dose.
Because immune responses to vaccination before the first birthday may be less reliable, those children still need the recommended routine doses later.
Adults without evidence of immunity may also require vaccination, particularly when they work in healthcare, travel internationally or belong to communities experiencing outbreaks.
People who are uncertain about their vaccination history should follow national guidance or discuss their circumstances with a healthcare professional.
Is the measles vaccine safe?
The MMR vaccine has been used for decades and has undergone extensive safety evaluation.
Most side effects are mild and temporary, including soreness around the injection site, fever or a temporary rash.
A small number of vaccinated children may experience a febrile seizure associated with fever. Serious allergic reactions are extremely rare.
The combined MMRV vaccine may carry a slightly higher risk of fever-related seizures after the first dose in young children compared with administering MMR and varicella vaccines separately.
One persistent concern has been the false claim that MMR vaccination causes autism.
However, extensive scientific research has not demonstrated a causal relationship between the vaccine and autism.
In a systematic review published on September 3, 2026, WHO examined evidence concerning vaccines and autism spectrum disorder and concluded that the most methodologically rigorous studies did not support a causal association.
The European Medicines Agency has reached the same conclusion after evaluating decades of research, including a large Danish study involving more than 650,000 children.
The risks associated with measles infection are substantially greater than the risks of serious adverse events from vaccination for people eligible to receive the vaccine.
Why can't everyone receive the MMR vaccine?
The MMR vaccine contains weakened live viruses that stimulate immune protection without normally causing the diseases themselves.
Because of this design, the vaccine is not suitable for everyone.
It is generally contraindicated during pregnancy and for people with certain forms of severe immune suppression.
Individuals who have experienced a severe allergic reaction to a previous dose or a vaccine component may also require an alternative clinical approach.
Some patients receiving cancer treatment, undergoing organ transplantation or living with serious immune disorders cannot safely receive live vaccines.
Infants younger than six months are also generally too young to receive the vaccine.
These groups depend partly on high vaccination coverage among people around them to reduce the likelihood of exposure.
That protection is known as community immunity and is one of the principal reasons public health authorities emphasise maintaining high vaccination rates.
What should someone do after possible measles exposure?
People who believe they have been exposed to measles should seek medical or public health advice promptly, particularly if they are unvaccinated, have uncertain immunity or belong to a high-risk group.
Preventive treatment may still be possible after exposure, but the time available is limited.
According to the CDC's post-exposure vaccination recommendations, the MMR vaccine can provide protection or modify the severity of illness when administered within 72 hours of initial exposure.
For certain vulnerable individuals, immunoglobulin treatment may be administered within six days of exposure.
Immunoglobulin contains antibodies that provide temporary protection and may reduce the risk of infection or serious complications.
It is particularly relevant for susceptible infants, pregnant women and severely immunocompromised patients who cannot receive the live vaccine.
Treatment decisions depend on the individual's immunity, medical history and the timing and circumstances of exposure.
Anyone developing symptoms after suspected exposure should contact healthcare services before arriving in person so that appropriate infection-control arrangements can be made.
How long should someone with measles remain isolated?
Isolation is essential because people with measles can infect others both before and after the rash appears.
According to CDC guidance, patients should generally remain isolated for four days after the rash begins, with the day of rash onset counted as day zero.
Healthcare settings require airborne infection-control precautions, including appropriate isolation rooms and respiratory protection for staff.
People with severe immune suppression may remain infectious for longer and require individual medical assessment.
Close contacts without adequate immunity may also need to avoid school, work or other settings for a period determined by public health authorities.
These measures help prevent a single infection from developing into a much larger outbreak.
However, isolation and contact tracing are considerably more effective when combined with high community vaccination coverage.
Why international travel remains a major measles risk
International travel allows measles to move quickly between countries, including from regions with sustained transmission into communities where the disease has become relatively uncommon.
A traveller may become infected abroad and return home before developing symptoms, potentially exposing other passengers, family members or colleagues.
Airports, public transport, hotels and crowded events create opportunities for exposure, particularly among people without adequate vaccine protection.
According to the CDC's updated measles travel guidance, international travellers should ensure they have appropriate immunity before departure.
For individuals who require vaccination, protection is ideally established at least two weeks before travelling, although vaccination may still be worthwhile when departure is closer.
Travel-related risk is not limited to countries traditionally associated with measles. Outbreaks have occurred in European destinations, North America and other regions with otherwise advanced healthcare systems.
The important consideration is whether measles is circulating at the destination and whether the traveller has adequate immunity.
Why measles remains dangerous despite decades of vaccination
Measles provides one of the clearest examples of how vaccination can transform the global burden of an infectious disease.
Before widespread immunisation, the virus caused millions of deaths annually. Today, effective vaccination programmes have reduced mortality dramatically.
According to WHO estimates, measles vaccination prevented nearly 59 million deaths between 2000 and 2024.
Nevertheless, approximately 95,000 people still died from the disease in 2024, and outbreaks continued affecting multiple regions during 2025 and 2026.
The renewed spread of measles demonstrates how quickly progress can be reversed when vaccination coverage declines or large groups of people remain unprotected.
For most patients, the infection resolves within weeks. But pneumonia, brain inflammation, immune-system disruption and the rare possibility of SSPE mean its consequences can be far more severe than the familiar childhood rash suggests.
The central message from health authorities is therefore straightforward: measles remains highly contagious and potentially dangerous, but it is also one of the serious infectious diseases that can be prevented effectively through vaccination.
Ensuring that children and susceptible adults receive appropriate protection remains the most important measure for preventing infections, reducing deaths and limiting the return of major outbreaks.
This article is made and published by Aksel Kryhlmand, who may have used AI in the preparation.