How dangerous is measles?

For hundreds of years, measles has been one of the most contagious and lethal viruses known to humans. Especially for those who have not received a measles vaccination – and for babies, children, pregnant women, and for those with comorbidities, in particular – it remains so today. 

As well as hospitalization and death, measles can cause long-term, debilitating health complications. It also can damage the immune system by "deleting" its memory of how to fight infections, leaving measles survivors vulnerable to other diseases like influenza for weeks or even months. 

After the measles vaccine became publicly available in 1963, such complications from measles plummeted alongside the overall case rate. (Read more about what we know about the MMR vaccine and its safety). 

The majority of children worldwide are vaccinated today. Yet in areas with less vaccination coverage, or where vaccine uptake is declining, fresh outbreaks show just how deadly the disease still can be. In the Democratic Republic of the Congo from 2018-2020, for example, an Ebola outbreak killed 2,299 people. In the same period, a measles outbreak killed 7,800 people – three times as many people.

Globally, in 2022, measles deaths worldwide rose 43 per cent compared to 2021, a result of lower vaccination rates during the Covid-19 pandemic. About 373 people die from measles every day. 

Part of the problem is that measles is far more contagious than other viruses, including Covid-19, influenza and varicella (chickenpox). For every one person who has measles, 12 to 18 other people will be infected. This makes measles around 12 times more contagious than influenza, six times as contagious as Ebola, and twice as contagious as Covid-19 and chickenpox. This is partly why recent measles outbreaks have spread so quickly, particularly among populations with lower rates of vaccination.

How dangerous is measles for children?  

While measles can be risky for anyone, it is especially dangerous for children, particularly children under five years of age who are not vaccinated. This is because children's immune systems and their organ systems are still developing, making them more vulnerable both to infection and to health complications.   

Every year, around 136,000 people worldwide die from measles and the complications caused by the disease. Most of them are children. 

In 2000, before the measles vaccine was as widely available as it is today, 761,000 children died from measles and its complications every year. 

The most common measles symptoms include a cough, running nose, and fever, typically followed by a rash. While they might sound mild, these symptoms, and other complications caused by measles, can be severe. Of all children who contracted measles in the WHO European Region in 2023, more than half had to go to hospital. 

If your child has symptoms like fever and rash, it’s important to visit a doctor immediately. Prompt diagnosis and treatment are essential to manage the disease effectively and prevent complications. Early intervention helps protect not only the individual but also the broader community by reducing the risk of spreading the infection. 

In 2023, out of 322,714 officially reported global cases of measles, 60,941 occurred in Europe and Central Asia. This highlights the significant impact of measles in these regions and underscores the importance of vaccination to prevent the spread of this serious disease. 

Children who have weakened immune systems, such as pre-existing conditions or malnutrition, are most at risk. But complications can affect anyone, and it is not always apparent in advance who will be affected most. 

In middle and upper income countries, out of every 1,000 children who contract measles, 70 to 90 children will develop an ear infection, 80 will develop diarrhoea, and 10 to 60 will develop pneumonia, a lung infection which can be especially risky for young children. 

Around one in every 1,000 to 2,000 children with measles will develop post-infectious encephalitis, inflammation of the brain which can cause a coma and death.  

While death from measles is rare in middle and upper income countries, it can occur. In the US, for example, it is estimated that for every 1,000 children who contract measles, one or two will die. In lower income countries, the risk is far higher: for every 1,000 children who contract measles, 30 to 60 will die. In some populations – such as children who have been displaced – around 300 children will die of every 1,000 who contract measles.   

Measles can have a significant impact on the immune system, including the deletion of immune memory. Research indicates that measles can erase the immune memory of previous infections and vaccinations, a condition known as "immune amnesia." This effect means that the immune system forgets how to fight off previously encountered pathogens, increasing susceptibility to other infections.

Studies have found that measles can reduce the immune memory of previously acquired infections by up to 30%. This loss of immune memory can persist for months or even years, leaving individuals vulnerable to diseases they were previously protected against. This underscores the importance of vaccination to prevent measles and its potential to compromise the immune system.

One very rare, but lethal complication that can arise in measles-infected children is a specific type of encephalitis called subacute sclerosing panencephalitis (SSPE), which affects one in 100,000 cases. This viral infection lies dormant in the body for six to eight years before neurological symptoms start. These include loss of motor skills (like the ability to walk), loss of hearing, loss of vision, and brain damage. Within a couple of years, the disease normally progresses to a coma and death. Because there is no cure, the only way to prevent SSPE is to not contract measles to begin with. 

For all health complications and for deaths, the vast majority of affected children are those who have not been vaccinated. Of children under age five who contracted measles in 2023, 99 per cent had not received the two recommended doses of the measles vaccine. 

How dangerous is measles for babies?  

Infants under one year of age are the single most affected group. They are also the most likely to develop health complications like pneumonia, diarrhoea, and encephalitis, as well as to die. 

Babies are especially vulnerable to measles because, in many countries, children do not receive the measles vaccination until at least one year of age. It is also partly because babies have the weakest immune systems and because their organ systems are still developing.   

Until a higher proportion of the population is vaccinated around the world, babies will continue to be vulnerable. This is because 95 per cent of a population must be vaccinated in order to prevent outbreaks in general. But just less than three-quarters – 74 per cent – of children globally have received the two doses that are advised.   

How dangerous is measles for adults? 

Measles primarily affects children, but adults can also contract and spread the disease, especially if they are unvaccinated or have waning immunity. Studies have shown that adults can make up about 10 to 20 per cent of measles cases during outbreaks. This is concerning because adults who contract measles can spread the virus to children who are more vulnerable to severe complications. 

How dangerous is measles in pregnancy? 

Measles is also high-risk for both women in pregnancy and for the foetus.

The most common complication of measles for pregnant women is pneumonia, which affects around 18 out of every 100 pregnant women. Around four in 100 pregnant women die if they contract the disease. Measles can put the developing foetus at risk, too. It is estimated that out of 100 pregnant women who contract measles, around 13 give birth prematurely. 

Because it is generally advised that pregnant women do not receive the measles vaccine, this makes it especially important that people are vaccinated well in advance of any chance of falling pregnant, ideally in childhood.  

The first dose of the MMR vaccine, which protects against measles, mumps and rubella, should be given at 12 months of age. The second dose should be given at six years. Two doses of the vaccine protect 99 per cent of people exposed to measles from contracting the virus.