A cross-sectional study of Bordetella pertussis seroprevalence and estimated duration of vaccine protection against pertussis in St. Petersburg, Russia.

Background: In Russia as in other countries introduction of infant vaccination against pertussis in 1950s led to dramatic decrease of whooping cough. The current vaccination schedule includes a 3-dose infant series and toddler booster; the pre-school booster was cancelled in 1980s and never reintroduced. Whole-cell vaccines, and in a smaller proportion acellular vaccines are used for all doses. However, pertussis incidence in urban settings is high with highest burden in school children. We conducted a study of seroprevalence of recent pertussis infection to estimate the duration of protection from the 4-dose series.

Materials And Methods: Sera sample from 395 St Petersburg children aged ≥3 years and <14 years were tested for pertussis toxin antibodies using a commercial PT ELISA test. Only children with completed 4-dose vaccination course were included in the study. Age-specific seroprevalence of recent pertussis infection was analyzed for trends.

Results: Children fully vaccinated against pertussis at 3 years old had significant delays in infant vaccination schedule: only 83.5% received at least one dose of pertussis vaccine at 6 months of age and 25.6% received their toddler booster before 24 months-old. Overall, 10.6% of children demonstrated the serological signs of the infection in the last 12 months. A clear trend (r = 0.692) of increasing proportion of infection in the last 12 months was observed in children who had received their last dose of vaccine 6 years and more prior to the study.

Conclusion: Our study demonstrates that Russian children become susceptible to infection at or soon after entering school. The results confirm the waning of vaccine-elicited immunity around school-age and support the need for a booster dose at that age.