Safety and immunogenicity of live attenuated cold-adapted influenza B/Ann Arbor/1/86 reassortant virus vaccine in infants and children

Influenza B virus (IBV) is an important cause of febrile (fever-causing) respiratory disease in children. IBV infections account for a significant percentage of school absenteeism during outbreaks. They have been strongly associated with Reye's syndrome, a frequently occurring fatal disease associated with influenza and varicella (chickenpox) infections. Inactivated IBV vaccines provide variable response levels in recipients. A cold-adapted live influenza vaccine was prepared by assembling specific hemagglutinin (HA) and neuraminidase (NA) genes from the influenza strain known as B/Ann Arbor/1/86, and RNA segments from a donor virus, influenza B/Ann Arbor/1/66. This new virus vaccine was administered to 13 seropositive children (who had IBV antibodies, an indication of prior infection). Five seropositive children received placebo. The morbidity (rate of illness) in the vaccinees was lower than in the placebo group, and the vaccine was demonstrated to be safe in seropositive children. Subsequently, 57 seronegative children (without antibodies against IBV) were studied; 37 received vaccine, and 20 were given placebo. Increased levels of antibodies against IBV were identified in the seronegative vaccine recipients. The new vaccine was found to be immunogenic, safe and phenotypically stable, occasionally producing mild upper respiratory disease, in seronegative infants and children. (Consumer Summary produced by Reliance Medical Information, Inc.)