Why has measles, the almost eliminated disease, returned?

BarcelonaIn less than two months, 110 cases of measles have been diagnosed in Spain, 17 of them reported in Catalonia. Last year, 217 were identified, according to the State Network for Epidemiological Surveillance. These data confirm a clear acceleration of infections, but the researcher at the National Center for Epidemiology-Carlos III Health Institute (CNE-ISCIII) Noemí López Perea assures that the majority of infections are imported and that, therefore, the State has not lost the status of elimination of the disease granted by the WHO.

The uninterrupted rise in cases registered throughout the world since 2023 and the fact that a dozen outbreaks are being investigated in Spain - the largest in the Basque Country, with nearly fifty affected and a hospital involved in the spread - occupies the experts, who point to two elements as priority causes of illness.

But what is behind this increase in cases? Since 2014, neither Spain nor Catalonia have had continuous transmission of measles and most infections are contracted in another country. Once here, the infections occur in family groups. "They tend to be outbreaks of less than ten cases, which is to be expected in a situation where the disease has been eliminated. We should not worry the population because the virus is not circulating," says López Perea. However, the spokesperson and senior member of the Spanish Association of Vaccinology (AEV), Fernando Moraga-Llop, recalls that in 2017 there was a "re-emergence" of this highly contagious viral disease in the world.

The expansion of measles is temporarily contained due to the coronavirus pandemic - which eclipses the circulation of any other pathogen - but at the same time the vaccination coverage of a significant part of the world's population is interrupted. "Everything indicates that we will reach 2023 with a number of measles cases thirty times higher than in 2022," adds the pediatrician, who cites official data from the World Health Organization (WHO), in a briefing organized by SMC Spain.

Focus on nearby countries

Although tracing the origin of a virus is very complex, there are currently two very important active foci in our environment: one in Morocco, where since September 2023 there have been 25,000 infections and more than a hundred deaths, and another in Romania, with more than 2,000 cases and about twenty deaths. Faced with this surge, in Spain all the autonomous communities have been reinforcing the recommendations for vaccination against measles, especially in unvaccinated adults or those who have not had the disease, but no specific campaign has been started.

In Catalonia, since last May, vaccination has been offered to all people between 44 and 58 years old who go to their health centre the option of getting vaccinated against measles. The Government made this decision arguing that the age group of those born between 1966 and 1980 is one of the most vulnerable groups, since systematic vaccination against the disease began to be implemented in 1981. For those born in 1965 or before, it is considered that, very probably, it has already been considered that, very probably, it has already been very probably.

"But the data from the seroprevalence study [antibodies to the virus in the blood, whether from vaccination or from infection] have shown that those born between 1968 and 1977 would have a protection of more than 98%. Thus, those born from 19 onwards are the susceptible group," says the CNE-ISCIII researcher. Children, on the other hand, have almost optimal vaccination coverage throughout the State.

The problem with the second dose

The measles vaccine is part of the triple viral vaccine (it includes immunisation against this disease, rubella and mumps) and is administered in two doses within the common childhood vaccination schedule; one at twelve months and another at three years. Experts agree that coverage in Spain is "excellent" compared to that of neighbouring European countries and that Catalonia and the autonomous cities of Ceuta and Melilla have the most complete schedules in the State.

However, the main problem is the second dose: while practically all those born in Catalonia or Spain receive the first injection (97.8%), the percentage of people with the complete schedule falls to 91% or 93%, depending on the area. "The second dose has always been a little below [the WHO recommendation, which is 95%]; we are close to it, but the objective has never been reached," says Fernando Moraga-Llop.

The pediatrician stresses that in large cities there may be areas with less protection, around 50%, and that it is in these spaces where prevention actions must be intensified and vaccines recommended. "I think that in Spain we should not be in a state of alarm, but rather of alert," Llop stresses. López Perea agrees: "There are not large pockets of susceptible people and the responsibility, which falls on the regional governments and their epidemiology and public health services, is carried out very well at the local level."

Reluctance

On the fact that in recent years some reluctant or anti-vaccine discourses have been strengthened outside countries where they have historically had a lot of weight, such as France or the United States, and large outbreaks are proliferating in countries where vaccines are viewed with distrust for political reasons or less access to the health system - such as Romania, where the injections have been installed in Spain. For experts, it is important to emphasize that the current mobility, both of migrants and tourists, increases the risk of people reluctant to get vaccinated entering the country.

"The job of the health system is to identify these populations and carry out educational tasks," says the epidemiologist. And how can this social approach be made? There are classic methods such as asking susceptible people (by age or origin) during a routine or scheduled visit to primary care if they remember having received the vaccine and offering it to them if they do not, or recruiting travelers to international medical services, especially if they are going (or coming) to countries where measles circulates more rapidly.

But currently the most important strategy – and the one that can bear the most fruit, according to experts – is community awareness-raising work. It is a good strategy to break down linguistic barriers (with translators) and ideological barriers (with information). A good action to take is to approach groups that are reluctant or unaware of the vaccine through representatives of their own groups. "We should not point out people as responsible for an infection, but as people susceptible to getting sick," concludes López Perea.