Pertussis Seroprevalence in Korean Adolescents and Adults Using Anti-Pertussis Toxin Immunoglobulin G

This study was conducted to evaluate age-specific seroprevalence of pertussis in Korea and to formulate a strategy to prevent and reduce the incidence of pertussis. Residual serum samples of healthy adolescents and adults 11 yr of age or older were collected between July 2012 and December 2012, and anti-pertussis toxin (PT) IgG titers were measured using a commercial ELISA kit. We compared the mean anti-PT IgG titers and seroprevalence of pertussis of the six age groups: 11-20, 21-30, 31-40, 41-50, 51-60, and ≥ 61 yr. A total of 1,192 subjects were enrolled. The mean anti-PT IgG titer and pertussis seroprevalence were 35.53 ± 62.91 EU/mL and 41.4%, respectively. The mean anti-PT IgG titers and seroprevalence were not significantly different between the age groups. However, the seroprevalence in individuals 51 yr of age or older was significantly higher than in individuals younger than 51 yr (46.5% vs 39.1%, P = 0.017). Based on these results, a new pertussis prevention strategy is necessary for older adults. Graphical Abstract Keywords: Pertussis Vaccine, Prevalence, Korea, Vaccination INTRODUCTION The incidence of pertussis decreased with the introduction of the diphtheria-tetanus-whole cell pertussis (DTwP) vaccination in children around the world (1), and a decrease in pertussis was also observed in Korea where the DTwP vaccination has been universally recommended for infants and children since 1954 (2). However, pertussis began to rise in the 1990s in Europe and North America, especially in adolescents (1, 3, 4, 5), and it has been also observed since the 2000s in Korea (2). The increased incidence of pertussis was assumed to be caused by a waning vaccine effect after previous vaccinations, a decreased boosting effect by natural pertussis infections in a community, the emergence of mutated Bordetella pertussis species that differ from the vaccine strain, and improved diagnostic modalities (3, 4, 5, 6, 7). In the United States, since 2006, Tdap booster vaccinations at adolescence have been recommended to control the increasing pertussis incidence based on cost-effectiveness studies (8, 9, 10). An adolescent Tdap booster vaccination at 11-12 yr of age was also introduced in 2009 in Korea because the incidence of pertussis began to rise in the 2000s (2). Pertussis in adolescents and adults often presents with atypical manifestations, such as asymptomatic infections and a chronic cough, rather than typical pertussis symptoms, and because of this, the actual infection rates may be higher than the incidence and prevalence based on clinical diagnosis (11, 12, 13). Therefore, repeated seroepidemiological studies are necessary to understand pertussis epidemiology and seroprevalence in communities. We conducted this seroepidemiological study to evaluate the current status and periodic changes of pertussis prevalence in Korea after 2002 and 2008 (14).