Antitoxins for diphtheria and tetanus decline more slowly after vaccination with DTwP than with DTaP: A study in a Chinese population

Abstract

ObjectivesDTP vaccines are used for the prevention of pertussis, diphtheria and tetanus. In 2007, in Gaobeidian city, China, the DTwP vaccine was replaced with DTaP. This study described the diphtheria and tetanus sero-epidemiology in subjects vaccinated solely with DTwP or DTaP. MethodsBlood samples were obtained between October 2012 and June 2013 from 587 healthy subjects aged 2–17 years. Serum IgG antibodies against diphtheria and tetanus were determined using ELISA. Interrupted time series analyses examined the changes in antitoxin levels over time and analyzed the alterations in diphtheria and tetanus antitoxin levels after the vaccine switch. ResultsMean concentrations of diphtheria antitoxin and tetanus antitoxin were 0.074IU/ml (95% CI 0.065–0.084) and 0.063IU/ml (95% CI 0.053–0.076). The protection rates (antitoxins >0.01IU/ml) for diphtheria and tetanus were 88.25% and 82.11%. Mean antitoxin levels for both diphtheria and tetanus decreased with increasing age, but this decrease was much slower for DTwP than DTaP. ConclusionsAlthough the observed protection rates for diphtheria and tetanus were sufficient to prevent an outbreak at present, the means levels of diphtheria and tetanus antitoxins decreased with increasing age; therefore, booster vaccinations at 7 and 12 years of age would be strengthened in Gaobeidian city, China.