Population-Based Analysis of Vaccination Status and Post-Vaccination Adverse Events in Adults Aged 55 and Older

<b>Background/Objectives</b>: Older adults face increased vulnerability to infectious diseases such as influenza, pneumococcal infections, and COVID-19. Vaccination remains a key public health strategy, yet coverage and adverse event data in this group are limited. This study aimed to assess the prevalence of vaccination and the occurrence of post-vaccination adverse events among individuals aged 55 and older in Płock, Poland, with particular attention to gender and age differences. <b>Methods</b>: A population-based cross-sectional study was conducted between January and November 2022 among 2040 adults aged ≥ 55 years. Participants completed a structured questionnaire on vaccination history (past 3 years) and adverse events following immunization (AEFI). Cognitive eligibility was assessed using the MMSE (≥27). Statistical analyses included <i>t</i>-tests, chi-square tests, and Pearson correlation coefficients with a significance level of <i>p</i> < 0.05. <b>Results</b>: COVID-19 vaccination was reported by 86.9% of participants, influenza vaccination by 45.5%, and pneumococcal vaccination by 15.1%. Women reported significantly more adverse events following COVID-19 vaccination compared to men (16.1% vs. 8.8%, <i>p</i> < 0.001). A weak negative correlation was observed between age and number of vaccinations received (r = -0.088, <i>p</i> = 0.001), while age was positively correlated with adverse events following COVID-19 vaccination (r = 0.175, <i>p</i> < 0.001). Influenza vaccination was more common among men than women (50.7% vs. 43.4%, <i>p</i> < 0.05). <b>Conclusions</b>: Vaccination coverage among older adults in Płock was highest for COVID-19 but remained suboptimal for influenza and pneumococcal vaccines. Women reported adverse events more frequently than men. These findings highlight the need for targeted vaccination strategies and gender-sensitive communication approaches.