Update 23 April 2024

Measles has been in the spotlight in recent weeks. Apart from news about a large cluster of cases in Eindhoven, there have also been reports on travellers with measles. Yet there is no outbreak at the moment. In an outbreak of measles, infection rates are higher and it is unclear where and by whom the patients were infected. 

Early this year, the director of RIVM's Centre for Infectious Disease Control (CIb) decided to convene an Outbreak Management Team (OMT) due to an increase in measles cases across Europe. The purpose of the OMT is to see what needs to be arranged to prepare for the next outbreak. That this outbreak is coming is certain. In the Netherlands, a major outbreak occurs every 10-15 years. However, when exactly it will come is uncertain.

On 28 March, the OMT had a meeting on the subject of measles. Experts discussed what it takes to be properly prepared for an outbreak. This page contains an abridged and easier-to-read summary of their advice. You can download the full advice (in Dutch).  

In summary, the OMT’s main advice (for the general public) is that:

• it should be made easier for children to get a vaccination if they have not been vaccinated yet;
• siblings of children with measles should not attend day nursery until the incubation period is over;
• the Municipal Public Health Service (GGD) should give tailored advice in case of measles at a day nursery; 
• groups in day nurseries should, in such a case, have as little contact with each other as possible;
• children who have had direct contact with the measles patient should receive a vaccination or antibody injection if necessary;
• healthcare institutions should ensure proper protection of their healthcare staff;
• RIVM should maintain a stock of extra vaccines so as to be able to deal with a temporary peak in demand, for example due to catch-up vaccinations.

Why was the OMT formed?

An OMT usually meets when there is a threat of an infectious disease or a major outbreak. In such a case, an OMT usually meets once or twice to discuss the situation. The OMT also issues advice on possible measures. Previously, there were OMT meetings on, for example, meningococcal W disease, Q fever and human swine flu, and also on the last major measles epidemic in 2013/2014. For COVID-19, the CIb organised dozens of OMT meetings. This was an exception in a very special situation.

In the Netherlands, measles is known to cause a major outbreak every 10 to 15 years.  This is because the group of people who are not protected (by a previous measles infection or by a vaccine) keeps growing. After each outbreak, children are born who not vaccinated. The risk of an outbreak increases especially in areas with low vaccination coverage, where many unvaccinated people live together. In some areas, vaccination coverage has been low for many years. This has to do with the philosophy of life of many people who live in those areas. In recent years, however, vaccination coverage is decreasing even in big cities. The number of people with measles in Europe is also growing. It is likely, therefore, that there will soon be another measles outbreak in the Netherlands. 

RIVM was keen to gather all the knowledge from research and evaluations of the previous outbreak and discuss how things are currently developing in the Netherlands. That way, the Netherlands will be better prepared for the next outbreak. So this is why RIVM convened an OMT. The OMT members have all signed a declaration of interests.

What is measles?

Measles is a spotty disease. It is caused by a virus. Besides the familiar spots, several complaints are common among measles patients:

• nasal cold
• coughing
• high fever (above 39 degrees)
• eye infection

Sometimes the infection may be more severe, resulting in:

• ear infection
• pneumonia
• encephalitis
• in unprotected pregnant women: miscarriage or premature birth

Very occasionally, children die from measles infection.

In addition, a measles infection is known to reduce protection against other diseases for weeks or even years. This is because the measles virus infects white blood cells, which also protect the body against other infectious diseases.

2.1 The 2013/2014 outbreak

In the previous major measles outbreak, RIVM received a total of 2,700 reports of measles. Research has shown that only about 10% of all people who had measles were reported. So in fact about 10 times as many people were infected with measles (especially children of primary school age). Of this group, 180 patients were hospitalised. One person died during this epidemic, and one person died due to subacute sclerosing panencephalitis. This is a form of encephalitis caused by measles that only occurs several years after infection.

During the 2013/2014 outbreak, parents in some parts of the Netherlands were offered the possibility to get their children vaccinated earlier with the mumps-measles-rubella (MMR) vaccine. This concerned parents in municipalities with vaccination coverage rates below 90%. In the end, 5,800 children received early vaccination. Research has shown that earlier vaccination prevented about 10 to 100 measles infections.

2.2 Effects of measles on the immune system

Studies in patients of the 2013/2014 outbreak show that the measles virus infects white blood cells. This reduces the number of white blood cells. As a result, the protection of the body against other viruses and bacteria also decreases. This can last for months or even years. 

2.3 Modelling the spread of the virus

In retrospect, during the previous measles epidemic contacts in schools appear to have been important in spreading the virus. Children from reformatory families attend primary and secondary schools where vaccination coverage tends to be low. As a result, measles can easily spread from one school to another. Closing schools during a measles epidemic does not prevent the virus from spreading. This is because children can spread the virus even before they have obvious symptoms (such as the typical skin rash) and also have contact with each other outside school. 

Modellers have estimated the number of infections in a subsequent outbreak. If the situation is similar to the previous measles outbreak, modellers expect 2,400-2,800 reports of measles with an outbreak in 2024. With an outbreak in 2025, they estimate that, in a situation similar to the previous outbreak, there will be 3,100-3,200 reported cases. The researchers assume that the real number of infections will be about 10 times higher. The new situation with lower vaccination coverage in big cities has not been taken into account in there calculations.

Early vaccination

There is no major outbreak now like the one in 2013/14. There is no point in vaccinating people earlier, except for the direct contacts of a person with measles. The regular vaccination schedule provides the best protection against measles. Depending on the situation, in the event of a major outbreak this policy could be changed if it proved useful to do so. 

2.4 Long-term consequences of earlier vaccination

During the 2013/2014 outbreak, some children received vaccinations earlier than they would have under the regular National Immunisation Programme. The advantage of this is that the children concerned are protected from measles earlier. The effect of this has been studied. In children younger than 9 months, the vaccination is slightly less effective. In addition, long-term measles antibody levels are lower in children vaccinated earlier than in those vaccinated according to the regular schedule. As a result, a person vaccinated earlier than according to the regular schedule may have a higher chance of getting measles later in life than someone vaccinated according to the regular National Immunisation Programme.

2.5&2.6 Current state of affairs

At its meeting, the OMT discussed current developments in the Netherlands. This included a focus on clusters (related infections, where individuals have infected each other) in the south of the country. For the current situation, please refer to the ‘Measles’ page under ‘Topics’ on the RIVM website.

4.1.1 Catch-up vaccinations under the National Immunisation Programme

Children who have not been vaccinated can still get vaccinated until they turn 18. Vaccination is free. The OMT advises regional youth healthcare services to make this as easy as possible. The OMT also recommends informing parents about vaccination as effectively as possible. For example, by pursuing a neighbourhood-based or person-oriented approach. 

Healthcare professionals

The OMT advises healthcare facilities to make sure that their healthcare staff are well protected against measles. This also ensures that the healthcare workers themselves cannot infect patients.

4.1.3 Availability of vaccines

The OMT recommends ensuring that RIVM has a stock of additional vaccines. This will make it possible to deal with a temporary peak in demand for vaccines, for example due to catch-up vaccinations.

4.2 Policy concerning patient contacts

The OMT's advice is to offer MMR vaccination for children between 9 and 14 months of age who have had direct contact with a person with measles.  For children younger than 6 months in such cases, the OMT recommends immunoglobulins. These are antibodies against measles. Immunoglobulins remain effective for a shorter period than the measles vaccine. For children aged 6-9 months, the advice depends on the exact circumstances. The Municipal Public Health Service decides whether a patient’s contacts should get the vaccine or an immunoglobulin, and will make the necessary arrangements. 

4.3 Day nurseries

Many of the children who attend day nursery have not yet been vaccinated against measles. This allows the virus to spread easily. If there is a child with measles at a day nursery, the Municipal Public Health Service can give other children in the group the measles vaccine or an immunoglobulin (see 4.2). Siblings of a person with measles should not attend day nursery until the end of the incubation period (usually about 2 weeks). The OMT also advises day nurseries to try to minimise contact between different groups.
Surveillance

RIVM always tracks the number of reported cases of measles. RIVM uses its up-to-date picture for additional advice to prevent the spread of the virus as much as possible. RIVM will also look at how it can use sewage measurements to monitor measles infections.

Reported cases of measles by month in 2023 and 2024

The figure below shows reported cases of measles per month since January 2023. Case numbers are based on the available data up to 31 March 2024, and may still rise as reports come in. Case numbers from previous months may also still rise. This is because some reports are only received later.

Reported cases of measles, 1976–2024

The figure below shows reported cases of measles per year since 1976. The measles vaccine has been included in the National Immunisation Programme since 1976. Since it was introduced, there has been a very clear decrease in reported cases of measles, but a measles outbreak has occurred every 10–14 years. These major outbreaks primarily occur in areas with low vaccination coverage. The number of reported cases are significantly lower than the number of people who contract measles during a major outbreak. About 10% (1 in 10) infections were reported in the outbreak in 2013-2014.