Trial of bivalent influenza A vaccine in high-risk infants.

A vaccine trial involving 50 high-risk infants, aged six to 36 months, was performed for evaluation of the safety of a split-virus bivalent influenza A vaccine. After immunization, 18% of the infants developed a fever of greater than or equal to 100 F and 7% had fever of greater than or equal to 102 F. Other reactions to the vaccine were few. However, the reaction index of these high-risk infants to the bivalent vaccine was higher than those of older children receiving the same vaccine and normal infants receiving the monovalent vaccine. Forty-one percent of the infants responded with a titer of hemagglutination-inhibiting antibody of greater than or equal to 1:20 to the A/Victoria/75 component of the bivalent vaccine, and 35% responded to the A/New Jersey/8/76 component. This result suggested that this vaccine used in two doses would be an effective vaccine for infants. The infants generally tolerated the vaccine well. Nevertheless, the rapid development of fever would be of concern in the infant whose underlying disease was marginally compensated.