Effectiveness of inactivated influenza vaccine in preventing acute otitis media in young children: a randomized controlled trial.

CONTEXT Acute otitis media (AOM) frequently complicates influenza infection. Previous studies have found influenza vaccine effective in reducing the occurrence of AOM in children mainly older than 2 years. OBJECTIVE To evaluate the effectiveness of inactivated influenza vaccine in preventing AOM in children aged 6 to 24 months. DESIGN, SETTING, AND PATIENTS Randomized, double-blind, placebo-controlled trial of 786 children aged 6 to 24 months enrolled at Children's Hospital of Pittsburgh before the 1999-2000 (411 children) and 2000-2001 (375 children) respiratory seasons (defined as December 1 through March 31 of the respective following year). Children received influenza vaccine or placebo in a 2:1 ratio. The first cohort was observed for 1 year and the second cohort until the end of the ensuing respiratory season. INTERVENTION Two doses (0.25 mL each) of inactivated trivalent subvirion influenza vaccine or placebo were administered intramuscularly approximately 4 weeks apart. MAIN OUTCOME MEASURES Proportion of children who developed AOM, monthly occurrence rate of AOM, estimated proportion of time with middle ear effusion, and utilization of selected health care and related resources. RESULTS Of the 66 children in the vaccine group from whom serum samples were collected, seroconversion against strains in the vaccine formulations developed in 88.6% to 96.8%, depending on the specific strain. The efficacy of the vaccine against culture-confirmed influenza was 66% (95% confidence interval [CI], 34%-82%) in 1999-2000 and -7% (95% CI, -247% to 67%) in 2000-2001; however, influenza attack rates differed between these 2 periods (in the placebo group, 15.9% and 3.3%, respectively). Compared with placebo, influenza vaccine did not reduce the proportion of children who had at least 1 episode of AOM during the respiratory season (in the first cohort: vaccine, 49.2% vs placebo, 52.2%; P =.56 ]; in the second cohort: vaccine, 55.8% vs placebo, 48.3%; P =.17). The vaccine also did not reduce the monthly rate of AOM; the estimated proportion of time with middle ear effusion; or the utilization of selected health care and related resources. There were also no differences between the vaccine and placebo groups regarding any of these outcomes during peak influenza periods. The vaccines administered to both cohorts of children were well tolerated. CONCLUSION Administration of inactivated trivalent influenza vaccine to children aged 6 to 24 months did not reduce their burden of AOM or their utilization of selected health care and related resources.