1 in 4 outbreaks occurred in countries where it was eliminated and they observe “weak points” in the vaccine

The other is that the progress of recent years has petered out and some countries are returning to the path they have followed since then.

Over the past five years, measles cases have increased by 8%, according to a recent report from the World Health Organization.

Of the 59 large outbreaks that occurred last year, a quarter occurred in countries where the disease was considered eliminated, meaning more than 12 months had passed since the last endemic case.

The good news is that Deaths decreased by 11% between 2019 and 2024. Over the past year, around 95,000 people were registered, one of the lowest levels since 2000, when there were around 780,000 per year.

However, there is one outstanding problem: the vaccine is very effective, but to protect a population (that is, people who have not received it for whatever reason are not vulnerable), coverage must be at least 95%.

Globally, first dose coverage stands at 84%, slightly below pre-pandemic levels.

Spain, in this area, is one of the best placed countries. The coverage of the first dose is 96.65%, according to data from the Immunization Information System of the Ministry of Health.

So far, so good. However, At the second dose, although coverage remains high, it does not reach the desired level: 91.75%.

This figure, however, does not accurately reflect the variability that exists in the country, where six communities and one autonomous city (Balearic Islands, Canary Islands, Cantabria, Valencian Community, Madrid, Basque Country and Ceuta) do not reach 90%.

There is an additional problem. The measles vaccine has demonstrated high effectiveness, but this may vary depending on the age at which the first dose was administered.

The study of a recent outbreak in the French region Auvergne-Rhône-Alpes offers a reality that is sometimes little taken into account.

It is a region where, unlike others in France, it has high vaccination coverage, around 89% of both doses.

A work published in the magazine Eurosurveillance crumble the shoot. It occurred in a secondary school and affected 64 people, 57 children and 7 adults.

Vaccination coverage at the center was high: 93.5%. The epidemic affected 37 people vaccinated with two doses and 24 unvaccinated.. In other words, unvaccinated people were more likely to contract measles.

Among the latter, there were also three hospitalizations: two students and one adult.

Reduced effectiveness

The researchers, led by Thomas Bénet and Erica Fougère, from the regional unit of Public Health France, focused on vaccinated cases.

They found that the average age at which vaccinated cases received the first dose was 10.8 months, while among uninfected vaccinees it was 14.4 months.

This seems like a minor difference. After all, the entire measles vaccination program (offered along with rubella and mumps) includes two doses.

Currently, the first dose is usually given at 12 months. A few years ago, however, there was more variability and there are also exceptional situations which modify the recommendations.

For example, France experienced an epidemic situation around 2010-2011which led to vaccinating the first dose early: at 9 months, or even 6 months, in order to protect a baby exposed to the virus.

Researchers observed that vaccine effectiveness among students who received the full regimen and received the first dose at 12 months at the earliest exceeded 95%.

On the other hand, this figure drops to 83.3% if the first dose was administered between 9 and 11 months after birth, and to 60.7% if it was administered between 6 and 8 months.

Jose Gomez Rialspokesperson for the Spanish Society of Immunology, explains that it is “the transfer of maternal antibodies, which protect babies in the first months of life but neutralize the vaccine.”

The immunologist explains that there is great variability in the effect of this transfer. “It was clear at 6 months and many countries started vaccinating at 9 months, including France. In Spain, vaccination started at 15 months.”

Scientific evidence favors administering the first dose after 12 months, which Spain has done for many years.

“It is only recommended to give it at 9 a.m. if you are traveling to risk areas and this dose would not count for the vaccination schedule: two additional doses would be needed.”

In fact, France introduced the third dose in 2024 for cases where the first had been administered earlier. Eurosurveillance’s work supports this decision.

However, Gómez Rial highlights the importance of the second dose and warns that in recent years “there is a decline and this can generate a risk.”

Doubts about vaccination, even generated by unofficial organizations, are pushing some families to give up this second dose. They are few in number but, given the high coverage the vaccine needs to protect against measles, we must be vigilant.

“In Spain it is not alarming but there are regions with gaps in coverage. If this downward trend continues they will be more exposed.”