Influenza vaccine in healthy preschool children.

BACKGROUND

Studies of influenza vaccination in healthy children have not definitely answered the question of their efficacy.

METHODS

We have carried out a randomized trial in a well selected population of healthy preschool children in Sardinia, Italy. During October 1995, 344 children aged 1 to 6 years, were randomly assigned to receive influenza vaccine (n=177) or no treatment (n=167). Two doses of a trivalent subvirion vaccine, containing 15mg of highly purified surface antigens from the component strains A/Johannesburg/33/94-like, A/Singapore/6/86-like and B/ Beijing/184/ 93-like were administered. Follow-up data were collected from December 1, 1995 through April 30, 1996.

RESULTS

Seroconversion was documented in 17 out of 17 children. No specific systemic symptoms or severe local reactions were observed after vaccination. Influenza-like episodes, defined by the presence of fever and cough or sore throat that lasted at least 72 hours, occurred in 63 (37.7%) of unvaccinated children and in 22 (12.4%) of vaccinated ones. The corresponding reduction in disease incidence was 67% (95% CI: 0.59-0.74). Three episodes of otitis were observed among children in the control group versus zero among vaccinated children (p=0.07). Mean duration of day care center absenteism was significantly reduced by vaccination (2.3 days in unvaccinated and 0.5 day in vaccinated children, p<0.001)

CONCLUSIONS

Influenza vaccine is safe and effective in healthy preschool children. However the favourable implications of vaccination on disease rate in subsequent years have to be evaluated.