Estimation of populations at risk for severe influenza and vaccination coverage in Mexico, 2010-2021

Influenza remains an important cause of morbidity among populations with underlying medical conditions associated with increased risk of severe disease. This study aimed to estimate the size of populations eligible for influenza vaccination according to the Mexican Universal Vaccination Program and to evaluate vaccination coverage gaps among populations at risk in Mexico between 2010 and 2021.

A retrospective analytical study was conducted using epidemiological and administrative healthcare databases from Mexican public healthcare institutions. Population estimates were constructed using prevalence-based epidemiological projections, healthcare system records, and attended patient data from populations at risk. Descriptive analyses and time-series modeling were performed to evaluate vaccination coverage patterns and healthcare demand over time.

Across all analyzed populations at risk, the number of individuals receiving healthcare services was consistently lower than the number of notified cases and substantially lower than prevalence-based epidemiological estimates. Vaccination coverage varied considerably across populations at risk and remained incomplete throughout the study period. In 2021, although approximately 12.5 million influenza vaccine doses were administered among populations at risk, a substantial proportion of potentially eligible individuals remained unvaccinated. Forecasting analyses suggested a progressive increase in healthcare demand among populations at risk over time.

Important gaps persist between the estimated population at risk, diagnosed individuals, healthcare utilization, and influenza vaccination coverage in Mexico. The analytical framework proposed in this study integrates epidemiological prevalence estimates, healthcare utilization patterns, and vaccination data to identify unmet vaccination needs and may support improved public health planning, prioritization strategies, and strengthening of influenza vaccination programs in Mexico and similar settings.