Why is measles returning in 2025?, by Juan Gérvas

Measles is returning to the impoverished and wealthy world[1], from the United States[2] to the European Union[3], and is creating old problems that seemed to be overcome[4]. Why?

The explanation for the resurgence of measles is seemingly simple: the COVID-19 pandemic largely disrupted the vaccination schedule, leaving a portion of the world's population unvaccinated.

Furthermore, the controversy surrounding COVID-19 vaccines and the compulsory policy regarding them increased "vaccine hesitancy" and also contributed to the decline in vaccination coverage[5].

Beyond "Vaccine Hesitancy"

Vaccine hesitancy explanation for the decline in vaccine coverage is not sufficient.

It is important to look at the bigger picture because

1/ herd immunity is not working (even though there is over 95% coverage, as in Madrid, Spain, there are measles outbreaks[6],[7]);

2/ there are systematic failures in access to the vaccine (there are huge pockets of "unprotected" individuals; for example a growing number of immunocompromised people[8]); and

3/ we need a better measles vaccine, one with a lifelong effect, since antibody levels fade over time, especially twenty years after the last dose and in populations where natural cases of measles no longer occur (immunity is “boosted” over time by natural measles exposure)[9],[10],[11].

We need a better vaccine

In fact, the vaccine manages to maintain antibodies for about twenty years, and a third dose is already being considered, for example in New Zealand[12], but the third dose produces a weak response, lasting only five years at most. A better vaccine is therefore needed, one that mimics the natural immunity produced by measles itself. Literally: "Improving vaccine formulations to elicit stronger and longer-lasting immunity is essential for effective measles control and elimination[13]." We need a paradigm shift[14].

In fact, mothers vaccinated against measles in countries where there are no natural cases, as they grow older, transmit few antibodies that barely last 3-4 months to their newborns[15] who remain unprotected until they are vaccinated (in Spain, the first dose of the measles, mumps, and rubella, MMR vaccine, is given at twelve months).

In a well-studied outbreak in North America (Quebec, Canada) in 2011, almost half of the measles cases were properly vaccinated, with both doses correctly administered and documented[16].

There are other facts

For example, cesarean births are increasing worldwide, and children born by cesarean section have a poorer immune response to the measles vaccine[17],[18]. The first dose frequently fails because it doesn't produce a sufficient immune response, and until the second dose, at 3-4 years of age, the child remains unprotected.

In another example, children born between 1970 and 1980 have been exposed to few natural cases of measles in the community and were generally not adequately vaccinated, creating a "pocket of susceptibility."

Those born before 1970 often have lifelong antibodies, having had the disease or repeated contact with the wild virus during measles outbreaks in the community before the vaccine was introduced[19].

There are pockets of marginalization (due to poverty, ethnicity, etc.) that the vaccination does not reach. This was clearly demonstrated in Andalusia, Spain, where the largest outbreak occurred in Seville, in an area of exclusion, "in need of social transformation[20]."

As we have mentioned, the immunosuppressed population (under treatment with corticosteroids, monoclonal antibodies and chemotherapy for cancer and transplanted organ, with HIV infection, autoinmune diseases, etc.) has increased.

All of this creates an explosive mix that can be exploited with manipulative headlines of anti-immigration messages by attributing outbreaks and cases of measles to illegal immigrants[21].

Conclusion

The current measles outbreaks reflect complex problems, and it is simplistic to reduce the analysis and response to "vaccine hesitancy."

We need to

1/ reach the “pockets” of susceptible people (those born between 1970 and 1980, marginalized populations due to poverty, ethnicity, etc.),

2/ rethink the vaccination schedule, and

3/ urgently improve the vaccine.

Author

Juan Gérvas, MD, PhD, retired rural doctor, CESCA Team, Madrid, Spain, and former professor of public health at Johns Hopkins University, Baltimore, United States

jjgervas@gmail.com @JuanGrvas @juangrvas.bsky.social

References

[1] Measles could again become widespread as cases surge worldwide. https://theconversation.com/measles-could-again-become-widespread-as-cases-surge-worldwide-255501

[2] Measles cases and outbreaks. https://www.cdc.gov/measles/data-research/index.html

[3] Measles on the rise again in Europe. https://www.ecdc.europa.eu/en/news-events/measles-rise-again-europe-time-check-your-vaccination-status

[4] Measles 2025. https://www.nejm.org/doi/full/10.1056/NEJMra2504516

[5] A Review of the Resurgence of Measles, a Vaccine-Preventable Disease, as Current Concerns Contrast with Past Hopes for Measles Elimination. https://medscimonit.com/abstract/full/idArt/944436

[6] Seroprevalence of measles and rubella virus antibodies in the population of the Community of Madrid, 2008–2009. https://www.sciencedirect.com/science/article/pii/S1876034115000489

[7] Community-wide measles outbreak in the Region of Madrid, Spain, 10 years after the implementation of the Elimination Plan, 2011–2012. https://pmc.ncbi.nlm.nih.gov/articles/PMC5443381/

[8] Prevalence of Immunosuppression Among US Adults. https://jamanetwork.com/journals/jama/fullarticle/2815274

[9] Waning antibodies in measles and rubella vaccinees—a longitudinal study. https://www.sciencedirect.com/science/article/pii/S0264410X0501251X

[10] Waning immunity and subclinical measles infections in England. https://www.sciencedirect.com/science/article/pii/S0264410X04003202

[11] Persistence of Measles, Mumps, and Rubella Antibodies in an MMR-Vaccinated Cohort: A 20-Year Follow-up. https://academic.oup.com/jid/article/197/7/950/798890

[12] Cost-benefit analyses of supplementary measles immunisation in the highly immunized population of New Zealand. https://www.sciencedirect.com/science/article/pii/S0264410X17310034

[13] Seronegative vaccinees may not benefit from multiple booster doses of MMR vaccine in restoring immunity.  https://onlinelibrary.wiley.com/doi/10.1002/jmv.70135

[14] Measles, the need for a paradigm shift. https://www.jstor.org/stable/48693585

[15] Waning of measles maternal antibody in infants in measles elimination settings – A systematic literature review. https://www.sciencedirect.com/science/article/abs/pii/S0264410X18300264

[16] Largest measles epidemic in North America in a decade--Quebec, Canada, 2011: contribution of susceptibility, serendipity, and superspreading events. https://academic.oup.com/jid/article-abstract/207/6/990/898747?redirectedFrom=fulltext&login=false

[17] Dynamics of measles immunity from birth and following vaccination. https://www.nature.com/articles/s41564-024-01694-x

[18] Birth by C-section more than doubles odds of measles vaccine failure.  https://www.cam.ac.uk/research/news/birth-by-c-section-more-than-doubles-odds-of-measles-vaccine-failure

[19] Seroprevalence of Measles-, Mumps-, and Rubella-specific antibodies in the German adult population – cross-sectional analysis of the German Health Interview and Examination Survey for Adults (DEGS1) https://www.thelancet.com/journals/lanepe/article/PIIS2666-7762(21)00105-8/fulltext

[20] Outbreaks of Measles in Andalusia, Spain, during the Period 2010-2015. https://scielo.isciii.es/scielo.php?script=sci_arttext&pid=S1135-57272015000400009

[21] Are 'Illegal Immigrants' to Blame for Measles Outbreaks Across the U.S.? https://www.snopes.com/fact-check/immigrants-measles/