The Study and Its Key Findings
A comprehensive retrospective study over nearly two decades has uncovered systemic failures and critical shortcomings in Mexico’s vaccination program against Measles, Mumps, and Rubella (MMR). The research reveals that between 2006 and 2024, approximately 22.5 million doses of the MMR vaccine were not administered, accounting for 25% of the target population.
The Expert’s Warning
Dr. Rodrigo Romero Feregrino, a co-author of the study and coordinator of the Mexican Association of Vaccinology (AMV), has issued a critical warning. He states that Mexico is at risk of losing its measles elimination certification, granted in 2016, if the virus circulates for a continuous 12 months in any region where it was previously eradicated.
The Science and Current Outbreak
Dr. Romero emphasized in an interview with El Economista that the lack of coverage has underscored the importance of vaccines, especially in light of the ongoing measles and mumps outbreak. The study aimed to gather data from various sources—SSA, IMSS, and ISSSTE—to provide a clearer picture than administrative coverage figures, which are often overestimated.
“We found that, according to the target population that should have been vaccinated over the past 19 years, there is a segment of the population that was not immunized and thus remains unprotected against these diseases,” said Dr. Romero, the AMV coordinator.
He further explained that the risk of disease is real and aligns with seroprevalence studies documenting a deficit in protection against measles among the Mexican population.
The Data Dilemma and Herd Immunity
The study documents that 25% of the target population did not receive the MMR vaccine, a figure Dr. Romero describes as “significantly high” and directly impacting community protection.
To prevent outbreaks of a highly contagious disease like measles, the World Health Organization (WHO) and Pan American Health Organization (PAHO) require 95% vaccine coverage for the triple viral jab. “Without adequate coverage, our population remains unprotected, and we face risks of outbreaks like the current one. We need at least 90%, but WHO mandates 95% coverage,” Dr. Romero explained.
Dr. Romero identified inconsistent data in procurement, administration, and reporting of vaccine coverage as a transversal problem affecting various vaccines, including influenza, BCG, and HPV, where his team has published similar studies.
Proposed Solutions
One key proposal from AMV is the implementation of a nominal vaccination system, similar to those used in other countries. “We need a nominal vaccination system that allows us to track every individual born in the country, ensuring they are vaccinated and identifying those who aren’t for follow-up,” Dr. Romero stated.
Key Findings of the Study (2006–2024)
The main findings from the 19-year retrospective analysis of MMR vaccination in Mexico reveal a coverage crisis and inconsistencies in dose management:
- MMR Vaccine: Approximately 22.5 million doses were unadministered, representing 25% of the national target population who lacked necessary protection. National coverage fluctuated between 60% and 92%, consistently falling below the WHO-required 95%.
- SR Vaccine (Measles and Rubella): The study detected inefficiency in managing this rescue vaccine, with around 24.6 million doses purchased but not administered—approximately 28% of the total doses bought.
The study concludes that the situation is complex and demands a coordinated, immediate response from authorities and the public to avoid historical setbacks in the country’s public health and maintain the eradication of vaccine-preventable diseases.
