Securing long-term immunity: The possible necessity of supplementary measles vaccination.

Background: The global initiative to eliminate measles, spearheaded by the World Health Organization, has yet to achieve its intended goals. In Turkey, despite robust vaccination strategies, recent increases in measles cases have been attributed to vaccine hesitancy and irregular migration. This study evaluates measles serology within a pediatric population to determine the impact of vaccination regimens on immunity.

Methods: A retrospective study at Ankara Bilkent City Hospital analyzed serum measles IgG levels in children aged 1-18 years from January 2020 to August 2023. Exclusions were applied for individuals with positive IgM results, incomplete vaccinations, and immunocompromised conditions. Patients were categorized based on their M-M-R^®II vaccine status into those having received either one or two doses. Seropositivity was assessed using the ELISA method.

Results: Of the 686 children, 30.2% received a single dose, and 69.8% received two doses of the MMR vaccine. Overall, 70.7% exhibited positive IgG levels. No significant differences were found in IgG levels between those who received one dose and those who received two doses. However, a decline in IgG levels was observed with age, particularly notable in adolescents aged 14-18 years.

Conclusion: The study reveals seropositivity rates lower than expected, highlighting challenges in achieving WHO targets. This suggests a potential need for booster doses during adolescence to maintain protective antibody levels. The findings emphasize the importance of continued surveillance and research to adapt vaccination strategies effectively and prevent measles outbreaks, particularly considering the decline in antibody levels and diverse vaccination histories across populations.