Young children have a high incidence of influenza and influenza-related complications. This study compared the efficacy and safety of cold-adapted influenza vaccine, trivalent (CAIV-T) with trivalent inactivated influenza vaccine (TIV) in young children with a history of recurrent respiratory tract infections (RTIs). Children 6 to 71 months of age were randomized to receive 2 doses of CAIV-T (n = 1101) or TIV (n = 1086), 35 +/- 7 days apart before the start of the 2002-2003 influenza season and were followed up for culture-confirmed influenza, effectiveness outcomes, reactogenicity, and adverse events. Overall, 52.7% (95% confidence interval [CI] = 21.6%-72.2%) fewer cases of influenza caused by virus strains antigenically similar to vaccine were observed in CAIV-T than in TIV recipients. Greater relative efficacy for CAIV-T was observed for the antigenically similar A/H1N1 (100.0%; 95% CI = 42.3%-100.0%) and B (68.0%; 95% CI = 37.3%-84.8%) strains but not for the antigenically similar A/H3N2 strains (-97.1%; 95% CI = -540.2% to 31.5%). Relative to TIV, CAIV-T reduced the number of RTI-related healthcare provider visits by 8.9% (90% CI = 1.5%-15.8%) and missed days of school, kindergarten, or day care by 16.2% (90% CI = 10.4%-21.6%). Rhinitis and rhinorrhea, otitis media, and decreased appetite were the only events that were reported more frequently in CAIV-T subjects. There was no difference between groups in the incidence of wheezing after vaccination. CAIV-T was well tolerated in these children with RTIs and demonstrated superior relative efficacy compared with TIV in preventing influenza illness.

OBJECTIVE. The goal was to evaluate the safety, tolerability, and efficacy of an investigational, refrigerator-stable formulation of live attenuated influenza vaccine (cold-adapted influenza vaccine-trivalent) against culture-confirmed influenza, acute otitis media, and effectiveness outcomes in young children in day care over 2 consecutive influenza seasons. METHODS. Children 6 to <36 months of age who were attending day care were assigned randomly in year 1 to receive 2 doses of vaccine or placebo intranasally, 35 ± 7 days apart. In year 2, subjects received 1 dose of the same treatment as in year 1. RESULTS. A total of 1616 subjects (vaccine: 951 subjects; placebo: 665 subjects) in year 1 and 1090 subjects (vaccine: 640 subjects; placebo: 450 subjects) in year 2 were able to be evaluated for efficacy. The mean age at first vaccination was 23.4 ± 7.9 months. In year 1, the overall efficacy of the vaccine against influenza subtypes similar to the vaccine was 85.4%; efficacy was 91.8% against A/H1N1 and 72.6% against B. In year 2, the overall efficacy was 88.7%; efficacy was 90.0% against H1N1, 90.3% against A/H3N2, and 81.7% against B. Efficacy against all episodes of acute otitis media associated with culture-confirmed influenza was 90.6% in year 1 and 97.0% in year 2. Runny nose or nasal discharge after dose 1 in year 1 was the only reactogenicity event that was significantly more frequent with cold-adapted influenza vaccine-trivalent (82.3%) than placebo (75.4%). CONCLUSIONS. Cold-adapted influenza vaccine-trivalent was well tolerated and effective in preventing culture-confirmed influenza illness in children as young as 6 months of age who attended day care.

In a retrospective study, 80 episodes of nontyphoid salmonella (NTS) bacteremia in children were compared with 55 episodes in adults over a 10-year p