PERTUSSIS IMMUNIZATION WITH ACELLULAR VACCINES IN GHANAIAN CHILDREN

In the present study, the persistence of antibodies to pertussis antigens was assessed in 51 Ghanaian children immunized with one of two acellular vaccines and one whole cell vaccine in early infancy. The effect of a booster dose 1 year after primary immunization was also examined. Antibody titres to pertussis toxin (PT) and filamentous haemagglutinin (FHA) were measured 1 month and 1 year after primary immunization and 1 month after the booster dose. Although geometric mean titres (GMTs) to FHA were significantly higher in the two types of acellular vaccinees than in the whole cell vaccinees 1 month after primary immunization, GMTs to FHA and PT after 1 year were not significantly different in the three groups. Geometric mean titres to PT and FHA following the booster dose were significantly higher in the acellular vaccines than in the whole cell vaccinees. Seropositivity rates to PT and FHA in the acellular vaccinees, which were more than 93.3% 1 month after primary immunization, ranged from 50.0 to 77.8% after 1 year. In conclusion, the acellular vaccines did not produce higher antibody levels than the whole cell vaccine 1 year after primary immunization. The booster dose was essential to maintaining sufficient seropositivity to pertusis antigens.