EVALUATION OF LIVE ATTENUATED INFLUENZA VACCINES IN CHILDREN 6-18 MONTHS OF AGE - SAFETY, IMMUNOGENICITY, AND EFFICACY

Live attenuated, cold-adapted (ca) monovalent and bivalent influenza A vaccines were evaluated in seronegative infants (ages 6-18 months) in a double-blind placebo-controlled trial to assess safety and immunoge nicity. A total of 182 seronegative subjects received a single intrana sal dose (10(6.2) TCID50) of ca A/Kawasaki/9/86 (H1N1) or ca Anos Ange les/2/87 (H3N2), both as a bivalent vaccine, or placebo. Respiratory a nd systemic symptoms did not differ between groups after vaccination. Hemagglutination antibody seroconversions (greater than or equal to 1: 8) to H3N2 exceeded 90%. In contrast, seroconversions to A/Kawasaki/9/ 86 (H1N1) were significantly less frequent in bivalent ca vaccine reci pients (31%) than in monovalent ca H1N1 recipients (83%) (P <.002). Du ring a subsequent H3N2 epidemic, nasal washes were cultured for viruse s from any subject with respiratory illness. H3N2 infections documente d by virus isolation were reduced by 65% in ca H3N2 recipients compare d with placebo or ca H1N1 recipients (P =.01).