Randomised study of the possible adjuvant effect of BCG vaccine on the immunogenicity of diphtheria tetanus acellular pertussis vaccine in Senegaleseinfants

Following a study in Senegal (1990-1995) in which the relative efficacy of a diphtheria-tetanus-acellular pertussis vaccine (DTaP) was compared with t hat of a diphtheria-tetanus-whole-cell pertussis vaccine in children given a simultaneous injection of Bacille Calmette-Guerin (BCG) vaccine, this sub sequent study was conducted to evaluate the possible adjuvant effect of the BCG vaccine on acellular pertussis vaccine components. A second objective was to compare the immunogenicity of these components when administered in accordance with a 2-4-6-month (spaced) schedule or an accelerated 2-3-4-mon th schedule. In all, 390 healthy Senegalese infants were randomly divided i nto three groups of 130 infants. Antibodies to acellular pertussis componen ts were measured in serum samples obtained within 2 days of the first DTaP dose and 1 month after the third dose. BCG vaccine, given simultaneously wi th the DTaP vaccine, did not influence the immunogenicity of the acellular pertussis vaccine components when compared with separate administration of the two vaccines. Infants immunised according to a 2-4-6-month schedule had a significantly higher immune response than those immunised according to a 2-3-4-month schedule with respect to the response to pertussis toroid asse ssed by seroneutralisation on Chinese hamster ovary cells (P < 0.0001). The se results suggest that BCG and DTaP vaccines can be given simultaneously w ithout interference or enhancement and that more optimal immunogenicity is achieved with an extended than with an accelerated schedule.