A newly published trial has shown that inactivated trivalent influenza vaccine did not reduce the incidence of acute otitis media among children 6-24 months of age.

A randomized trial of inactivated trivalent subvirion influenza vaccine was conducted during 1999-2001 among 786 children ages 6-24 months. Children received two doses of vaccine approximately four weeks apart. Testing the 66 serum samples collected from children in the vaccine group showed seroconversion rates of 88.6-96.8%, depending on the specific strain. Vaccine efficacy against culture-confirmed influenza was 66% (95% CI, 34%-82%) in 1999-2000, and -7% (95% CI, -247%-67%) in 2000-2001. However, the influenza attack rates were 15.9% and 3.3%, respectively.

Compared to placebo, influenza vaccine did not reduce the proportion of children with at least one episode of acute otitis media in the first cohort (1999) during the influenza season (vaccine, 30.5% vs. 29.9%), during the respiratory season (vaccine, 49.2% vs. placebo, 52.2%; P = .56), or during the entire one-year follow-up period (vaccine, 57.3% vs. 61.9%, P = .35). Nor did it reduce the proportion in the second cohort (vaccine, 55.8% vs. placebo, 48.2%; P = .17). There were no differences between vaccine and placebo groups for the monthly rate of acute otitis media, the estimated proportion of time with middle ear effusion, or the use of health care and related resources.

Hal B. Jenson, MD, FAAP, chairman of the department of pediatrics and director of the Center for Pediatric Research at Eastern Virginia Medical School and Children´s Hospital of the King´s Daughter, said that the influenza vaccine for 2000-2001 did not have a significant effect on prevention of influenza in this age group.

Demonstrating this benefit with this number of patients was hampered, he said, because the incidence of influenza never reached epidemic proportions in this population during the study years.

"Age differences could account for some of the differences between this and previous studies if the proportion of viral respiratory infections caused by influenza is lower in younger children than in older children, or if the vaccine was less effective in preventing influenza in younger children than in older children," he said. "However, this study found no difference in antibody responses by age group."

Source: Hoberman A, et al. Effectiveness of inactivated influenza vaccine in preventing acute otitis media in young children. A randomized controlled trial. JAMA. 2003;290: 1608-1616.