Quantification of waning immunity after measles vaccination - evidence from a seroprevalence study.

The aim of this study was to quantify waning rates from seroprevalence data collected in a study of population with a high vaccination coverage and fixed vaccination schedule. Data were collected during the national Immunologic Survey in the Slovak Republic in 2018. The average waning rate after the first dose (age 1.5 - 10 years) is 9.7% per year from the geometric mean titre (GMT) value 2634 mUI/ml. The average waning rate after the second dose (age 10 - 33 years) is significantly lower, 4.8% per year from the lower GMT value 1331 mUI/ml. This decline in antibody levels suggests that vaccine-induced protection may be compromised and results in the increase in the proportion of seronegative/borderline individuals. These outcomes may provide a valuable source for critical assessment of direct and indirect effects of vaccination.