Long-term immunogenicity of a single dose of acellular pertussis vaccine in paediatric health-care workers

SummaryObjectiveMonitor the long-term immunogenicity of a single dose of acellular pertussis vaccine in health-care workers.DesignGerman health-care workers and child-care workers received a single dose of a monovalent acellular pertussis vaccine (PAC-Mérieux®) in an open-label study. Blood samples were taken before (n = 261), 4 weeks after (n = 246), 1 year (n = 187), 2 years (n = 53), 3 years (n = 134) and 4 years (n = 37) after vaccination. IgG- and IgA-anti-pertussis-toxin (PT), IgG- and IgA-anti-filamentous hemagglutinin (FHA), and IgG-anti-pertactin (PRN) were measured by ELISA.ResultsOf all subjects, 97.1%, 99.2% and 97.2% had an antibody response to PT, FHA and PRN, respectively. Four weeks after vaccination the median titres of IgG antibodies to PT, FHA and PRN were 314, 785 and 84 EU/l, respectively, and all vaccinees had an immune response to at least one pertussis antigen. IgA-anti-PT and IgA-anti-FHA responses were found in 63.4% and 96.3% of subjects with a median titre of 30 and 196 EU/ml, respectively. The titre of IgG-anti-PT decreased slowly with a median concentration of 76, 71, 71 and 63 EU/ml after 1, 2, 3 and 4 years, respectively. Secondary titre increases were observed in 0.5%, 3.3%, 5.6% and 12.5% of the vaccinees 1, 2, 3, and 4 years after vaccination.ConclusionIn German health paediatric care workers long-lasting immune responses with high antibody levels could be induced by a single dose of acellular pertussis vaccine. A renewed contact with B. pertussis antigens resulted in a measurable immune response to PT between 0.5% (1 year p.v.) and 12.5% (4 years p.v.).