Poliomyelitis seroprevalence in high risk populations of India before the trivalent to bivalent oral poliovirus vaccine switch in 2016

摘要

Introduction This study assessed the seroprevalence of neutralizing antibodies to all three polioviruses among the last cohort of infants aged 6–11 months who received the trivalent oral polio vaccine (OPV) before the trivalent (tOPV) to bivalent (bOPV) switch and had an opportunity to receive a full dose of inactivated poliovirus vaccine (IPV) introduced in the routine immunization schedule. Methods Serum was tested for neutralizing antibodies against polioviruses among infants residing in three different risk-category states for poliovirus transmission in India: Bihar, a historically high-risk state for polio; Madhya Pradesh, a state with low routine immunization coverage; Chhattisgarh, with lower acute flaccid paralysis surveillance indicators. Results A total of 1113 serum samples were tested across the three states. The overall seroprevalence was 98.5% (95% confidence interval (CI) 97.7–99.2%), 98.9% (95% CI 98.3–99.5%), and 94.4% (95% CI 93.0–95.8%) for poliovirus types 1, 2, and 3, respectively. The median antibody titres for corresponding serotypes were 575, 362, and 181. Infants who received five doses of tOPV showed respective seroprevalence rates of 98.7%, 98.7%, and 93.7% against types 1, 2, and 3 polioviruses. There was no significant difference in seroprevalence across the groups of IPV recipients. The median reciprocal titre across the groups of IPV recipients was significantly higher for poliovirus 3 ( p = 0.006). Conclusions The seroprevalence rates observed in this study are historically the highest in the series of serosurveys that India has conducted to assess population immunity against polioviruses. Poliovirus 2 seroprevalence was very high at the time of the tOPV to bOPV switch in India effected in April 2016.