Comparative seroepidemiology of pertussis, diphtheria and poliovirus antibodies in Singapore: Waning pertussis immunity in a highly immunized population and the need for adolescent booster doses

BackgroundWe assessed the seroepidemiology of pertussis, diphtheria and poliovirus antibodies in a cohort of highly immunized children, together with the burden of these diseases in Singapore.MethodsHospital residual sera collected between August 2008 and July 2010 from 1200 children aged 1–17 years were tested for the prevalence of IgG antibodies against Bordetella pertussis, diphtheria toxoid, and all three poliovirus types by enzyme-linked immunosorbent assays.ResultsWe found an overall seroprevalence of 99.4% (95% CI 98.8–99.7%) for diphtheria, and 92.3% (95% CI 90.6–93.6%) for poliomyelitis, along with no indigenous cases of these diseases since 1993. However, the seroprevalence for pertussis was 60.8% (95% CI 58.0–63.5%) only. Among the subjects who had completed three doses of pertussis vaccination by the age of 2 years (n = 1092), the pertussis seroprevalence was 85.0% (95% CI 79.7–89.2%) in those who received the last vaccination within a year before the study, and it decreased to 75.0% (95% CI 64.5–83.2%) and 63.1% (95% CI 50.9–73.8%) in those who had the last vaccination 1 year and 2 years before the study, respectively. The seroprevalence remained at about 50% for those whose last pertussis vaccination was administered 4 years and longer before the study.ConclusionsThe high seroprevalence for poliomyelitis and diphtheria confer solid herd immunity to eliminate these diseases in Singapore. In contrast, immunity against pertussis waned considerably over time, and routine boosters should be given to adolescents to ensure sustained immunity against pertussis.

► We assessed seroepidemiology of pertussis, diphtheria and poliomyelitis in Singapore.
► High seroprevalence for poliomyelitis and diphtheria confer solid herd immunity.
► Immunity against pertussis wanes considerably over time post vaccination.
► Boosters to adolescents may have led to the decline in notified cases of pertussis.
► Pertussis boosters should be given to adolescents to ensure sustained immunity.