Antibody response of infants to two doses of inactivated poliovirus vaccine of enhanced potency
E. A. Simoes, B. Padmini, M. C. Steinhoff, M. Jadhav and T. J. John
The conventional formulation of injectable poliovirus vaccine (inactivated)
contains 20, 2, and 4 D-antigen units of types 1, 2, and 3 polioviruses.
Primary immunization requires three doses given at intervals of at least
four weeks. A new formulation with 40, 8, and 32 D-antigen units of the
three poliovirus types has been prepared to reduce primary immunization to
two doses. We evaluated the immunogenic efficacy of this new formulation
supplied to us as a liquid vaccine containing diphtheria-pertussis-tetanus
vaccines and inactivated poliovirus vaccine. Two doses were administered
four weeks apart to 100 infants and eight weeks apart to 114 infants.
Antibody titers were determined against the three types of polioviruses
before and after immunization. The effects of age, presence of maternal
antibody, and interval between doses of the frequency and titers of
antibody response were assessed. Irrespective of age or interval between
doses, the seroconversion rates to types 1 and 3 antigens were 90% to 100%.
To type 2 antigen the rate was below 84% in the 6- to 7-week-old infants,
88% to 95% in 8- to 12-week-old infants, and 90% to 100% in 13- to
45-week-old infants. The seroconversion rates and geometric mean titers of
antibody were lower in those infants with maternal antibody than in those
without maternal antibody at the time of receiving the first dose. The best
results were in infants 8 weeks of age or older, in whom the two doses were
given eight weeks apart. We recommend this schedule.
