Immunogenicity and reactogenicity of an acellular, monovalent 4-component pertussis vaccine as a booster dose in pre-school and early schoolage children

Aim of the study was to evaluate reactogenicity and immunogenicity of a monovalent, acellular 4-component pertussis vaccine (pertussis toxin = PT, filamentous haemagglutinin = FHA, pertactin, fimbriae-type 2) when given as a booster dose after primary immunization with the same vaccine. Methods: After 3 immunizations against pertussis with 6 week intervals at the age of 15 months of 6 years, 165 children received a booster dose after a mean of 15 months. The course following immunization was documented in a standardized parent diary. Specific antibodies against vaccine antigens were determined from serum specimens obtained before and 4 weeks after the dose. Results: As expected antibody values before the booster dose had decreased compared to post 3rd dose values but still were 4 to 40-fold above pre Ist dose values. The 4th dose resulted in a pronounced boost with 9 (fimbriae type 2) to 24-fold (pertactin) titer rises. Antibody values against PT, FHA and Fimbriae-type 2 positively correlated with age of the vaccinees. The booster dose was well tolerated as were immunizations during the primary series before. Local reactions at the immunization site ranged from 2,6% (swelling) to 35,8% (redness) and were generally mild. Systemic reactions occurred at a maximal rate of 15,1% (temperature greater than or equal to 38 degrees C). Neither local nor systemic reactions were correlated with age of the vaccinees. Conclusions: This monovalent, acellular 4-component vaccine has been licensed in Germany since January 1994 for immunizations against pertussis for children at least 15 months of age. It showed excellent reactogenicity and immunogenicity for a broad age range (4th dose was applicated up to the 8th year of life). Since the presence of specific antibodies before immunization did not influence immunogenicity or reactogenicity, immunizations against pertussis with this vaccine can be commenced or continued after previous doses with whole-cell vaccine any time without previous antibody determinations.