Spray more effective at warding off influenza

Among children who received the live vaccine, FluMist, there were 54.9% fewer cases of flu than among those who received the standard attenuated vaccine, said Dr Robert Belshe, of the Saint Louis University Health Sciences Center, and colleagues.

The spray also dramatically reduced the risk of flu-related ear and lower respiratory tract infections, said the team. The findings were published in the New England Journal of Medicine.

The research team enrolled more than 8,000 preschool children in 16 countries and randomly assigned them to either the live or the inactivated vaccine from October 20 to 29, 2004.

In the FluMist group, there were 153 cases of culture-confirmed flu, compared with 338 cases among the children receiving the inactivated vaccine. FluMist vaccination resulted in 89.2% fewer cases of influenza A/H1N1 and 79.2% fewer cases of influenza A/H3N2. There were also 16.1% fewer cases of influenza B, but the difference was not significant, say authors.

Among previously unvaccinated children, wheezing within 42 days after the administration of dose one was more common with live attenuated vaccine than with inactivated vaccine, primarily among children six to 11 months of age. In this age group, 12 more episodes of wheezing were noted within 42 days after receipt of dose one among recipients of live attenuated vaccine (3.8%) than among recipients of inactivated vaccine.

The incidence of serious adverse events was similar between the groups, the researchers said, but the rate of hospitalisation within 180 days for any cause among children ages six to 11 months was significantly higher in the FluMist group.

Taken together, they said, those findings “will restrict the use of live attenuated vaccine in children younger than one year and in children 12 to 47 months of age who have a history of asthma or wheezing.”

The live vaccine is not yet approved for children under the age of five years.