Seroprevalence of measles antibodies in Northwestern Russia population in 2012-2023.

Background: Measles is a highly contagious viral infection that may cause life-threatening disease, especially in children. The main approach for measles prevention and elimination is vaccination and support for strong immunity in 95% of the population. Although the mandatory measles immunisation was introduced in 1972 in Russia, the infection is still widespread in the country. We summarise the data of twelve-year (from 2012 to 2023) surveillance of the IgG levels in the North-Western Russian population. Methods: The data for anti-measles IgG levels in 28,530 samples from healthy subjects from the Northwestern Russia population which were examined from January 2012 to December 2023 were statistically analysed. Results: IgG levels and seroprevalence are higher in subjects who were born before 1967 and were not admitted to the massive vaccination programs compared to the younger population. In the adult population covered by the single-dose vaccination program (i.e., born in 1971-1990), the seroprevalence level reaches 69 % (compared to >90% in the subjects born before 1967). The gain of seroprevalence to 61,7%, accompanied by a decline of mean IgG levels, was demonstrated in subjects who were born in 1990 or later and covered by the MCV1+MCV2 vaccination according to the National vaccination schedule. Conclusion: These results reveal the necessity of vaccination coverage improvement, especially in the adult population. Also, more complex monitoring programs, including T-cell mediated immunity control, maybe more informative to estimate the actual anti-measles herd immunity.