Measles cases in Spain on the rise: from 34 in 2023 to more than 200 in 2024

Although there has been an increase in measles cases in Spain , from 34 cases in 2023 to more than 200 in 2024, our country is still in the situation of measles elimination, which has been maintained since 2016. According to data from the National Epidemiological Surveillance Network of the National Epidemiology Center , there has been no continued circulation of the virus since 2014.

However, Noemí López Perea , a researcher at the National Epidemiology Centre of the Carlos III Health Institute, said at a meeting organised by the Science Media Centre that we are occasionally experiencing "importations of the virus from countries where measles is still circulating. These imported cases can generate outbreaks of different sizes."

Currently, he said, in Spain we have an outbreak, with 110 confirmed cases, the majority in the Basque Country , where 41 cases have been confirmed, some in hospital settings and others in the family environment. At the national level, 34 cases have been imported and the rest are part of small, scattered outbreaks, with less than 10 cases each. “This is what is expected in an elimination situation.”

When the disease affects healthcare settings, the spread is usually greater. María del Mar Tomás, from the Spanish Society of Infectious Diseases and Clinical Microbiology , stressed the importance of healthcare professionals being aware of the importance of quickly detecting possible cases using molecular biology techniques to prevent the spread of the virus. "Sequencing the variants allows us to know the origin of the virus and anticipate its impact," she said.

Since measles was considered practically eradicated , he said, many health professionals do not take it into account when making differential diagnoses. Therefore, "it is essential to raise awareness among pediatricians and all health professionals about the use of rapid diagnostic techniques."

For paediatrician Fernando Moraga , although the situation in Spain is relatively stable, there is concern at a global level. In 2020, he said, "before the pandemic, there had already been warnings about the re-emergence of measles. Since 2017, there has been a significant increase in cases worldwide and the WHO recognised that the goal of eradication by 2020 was not achievable."

According to Moraga, from the Spanish Association of Vaccinology , although during the Covid pandemic, the incidence dropped, possibly due to the reduction in social interactions and the use of masks, it also became difficult to detect cases. However, "since 2022, measles has returned with a vengeance, and in 2023 the WHO reported a 30-fold increase in global cases compared to 2022. In fact, when reviewing the entire year, the real figure was a 65-fold increase. This spike - he stressed - is directly related to the drop in vaccination coverage ."

According to Moraga, with the data for 2023, the average coverage of the first dose is very good, 97.8%, although there are four communities below 95%. The second dose has lower coverage, with 11 communities below 95%.

In addition, he added, there are differences within cities. “A study of vaccination coverage by neighbourhood would reveal that, although a city may have an average of 97%, there may be areas where coverage is only 50%. This creates pockets of susceptible people who can facilitate outbreaks , such as the one that occurred in Granada a few years ago in a neighbourhood with low vaccination rates.”

The expert from the Carlos III Health Institute acknowledged that the second dose of the triple viral vaccine, which is administered between 3 and 4 years of age, has a lower coverage than the first. In 2012, the vaccination schedule was modified, establishing the first dose at 12 months and the second between 3 and 4 years of age, depending on the autonomous community. In Spain, "coverage for the first dose has always been over 95%, but the second dose has been slightly lower."

In this regard, he commented that in some specific areas, the vaccination rate for the second dose is less than 95%, allowing the virus to circulate and cause small outbreaks. Although the outbreaks are small, when added together they create the feeling that there is a massive increase in cases, he said.

Compared to our neighbouring countries, Spain is in a favourable position and has one of the most comprehensive vaccination schedules in Europe. However, Moraga warned that vaccine hesitancy is growing, although it is not just anti-vaccination groups.

Thus, López insisted that we are not in an alarming situation, "nor should we worry or alarm the population ." Although there are groups of susceptible people, they are not large pockets of vulnerable population.

And while it is true that between 2010 and 2012 there was a huge peak in Andalusia, we are now in a post-elimination period in Spain.

There has been no endemic circulation of the virus since 2014, so current cases are imported and generate small outbreaks. "There may be medium-sized outbreaks, such as the one we are seeing in the Basque Country, but this is largely due to transmission in hospital settings, where the spread of the virus is amplified," said López Perea.

In this regard, Tomás clarified that although the increase in cases is also due to the improvement in molecular techniques , we are now detecting many more cases. It is not an uncontrolled increase, but rather an improvement in detection.

In addition, he said, in a global context with a growing anti-vaccination movement, especially in the United States and Europe, "it is important to be aware of the risks. For example, in 2023, Romania recorded 80% of measles cases in Europe."

However, he wanted to send a clear message: measles has not been eradicated, but it is not a health crisis either. "It is a controlled disease as long as high vaccination coverage is maintained. Vaccinated people can become infected, but the effects are usually mild. The important thing is to continue to comply with the vaccination schedule."

Moraga pointed out another important point, which is the possibility of seeing more cases in children under 12 months . "These children are children of vaccinated mothers, and the passive immunity they receive through the placenta is less durable than in children of mothers who passed the disease naturally. This could explain some cases in infants of 9 or 10 months," he explained.

Therefore, although he does not believe that the first dose of the vaccine, which is currently administered at 12 months, should be brought forward, he does consider it urgent to bring forward the second dose, which is currently administered between 3 and 4 years, to 2 years. "This would facilitate access to the vaccine, since children have much more contact with the pediatrician in their first two years of life."

However, López indicated that changes to the vaccination schedule must remain within the appropriate framework. "Changing the vaccination schedule requires consensus within the Interterritorial Health Council , with the participation of all communities and experts, as well as an intense and exhaustive debate ," he said.

In fact, he added that the common calendar of the Interterritorial Council of the National Health System specifies that it is a common calendar, but not necessarily unique. In Spain there are currently different immunization calendars, although the differences are minimal. For example, Catalonia has an additional vaccine, while other communities do not administer it. As for the ages of administration, there may be small variations, but the calendar of the Interterritorial Council remains one of the best in Europe. " It is a common calendar, but the autonomous communities, due to their transfers of powers , can make some adjustments to the strategy, although not in all cases or for all doses."

As for protection in adults, those born in 1971 and later were considered to be the most susceptible. However, there are cohorts traditionally considered more susceptible because they were born before the introduction of the vaccine in 1981, when the incidence of measles was already declining. These individuals were neither exposed to the virus naturally nor received the vaccine.

However, cases of measles in properly vaccinated people are rare . A person is considered to be properly vaccinated if they have received the first dose after 12 months of age and the second dose at least one month apart, with well-preserved vaccines. Seroconversion with the first dose is 95%, and with the second dose it reaches 99.5%. Although cases of modified measles may occur in vaccinated people, it is rare.

In Spain, cases usually affect adults. Infections in young children are not common, as occurs in other countries with lower vaccination coverage. But in some sporadic cases, correctly vaccinated people can also become infected, especially in hospital settings, where exposure is greater. Fortunately, when this occurs, it is usually modified measles, a milder version of the disease with less contagious capacity.

As for vaccine hesitancy in Spain, experts agree that fortunately it is not a widespread problem like in other countries, where there are strong anti-vaccine movements. There are isolated cases of people who refuse vaccination, but not with the intensity seen in northern Europe or in certain groups in France and Eastern Europe, they said.

Moraga calls it vaccine hesitancy. "The measles situation in Spain is not alarming, but it is an alert. In 2023 there were 237 cases and in 2024 we have had 217. This indicates something," he warned.

Tomás stressed that it is necessary to identify susceptible people and offer them vaccination. In Spain, vaccination coverage is very high in the population born here, but it is important to ensure access to vaccination in more vulnerable populations. From a microbiological point of view, "I would recommend a rapid laboratory diagnosis in the event of any suspicion, as well as genomic characterization of the cases to prevent the spread of the virus and contain possible outbreaks."

Finally, López Perea stressed the importance of not stigmatising people, but rather identifying susceptible populations in order to intervene appropriately. “The work should focus on identifying these groups and offering them vaccination, without pointing out anyone as responsible for the spread of the infection.”