SAN FRANCISCO — A Finnish trial testing an investigational, refrigerator-stable version of the FluMist vaccine in healthy infants aged 6 weeks to 6 months suggests it might be given safely to babies below the recommended age of influenza immunization in the United States.
Irritability and runny nose/nasal congestion were more common in the younger half of the trial's infant population, but these and other reactogenicity events were mild, Dr. Timo Vesikari reported at the annual meeting of the Pediatric Academic Societies.
Adverse events, including fever, were similar for babies in intranasal vaccine and placebo groups.
“I believe further investigation of CAIV-T [cold-adapted influenza vaccine, trivalent] in young infants is warranted, but we should consider the present finding in the 6- to 16-week-olds,” Dr. Vesikari of the University of Tampere, Finland, said at the meeting, which was sponsored by the American Pediatric Society, Society for Pediatric Research, Ambulatory Pediatric Association, and American Academy of Pediatrics.
The study enrolled 120 healthy infants from May to December 2002. Dr. Vesikari and his colleagues stratified the population into two groups: 59 babies in a 6- to 16-week-old cohort and 61 babies in a 16- to 24-week-old cohort.
Each cohort was randomized to receive two doses of CAIV-T or placebo about 35 days apart.
Monitoring for reactogenicity 11 days after the first dose showed the 6- to 16-week-old cohort experienced nearly twice as much irritability (66.7% vs. 35.7%) and runny nose/nasal congestion (63.3% vs. 33.3%) as the placebo group. No differences were seen after the second dose. Among the older infants, the only difference seen after the second dose was that cough occurred more with the placebo group (39.3%) than with the children given CAIV-T (10.7%).
Dr. Vesikari said the investigators accepted Wyeth's invitation to do the trial in part because studies have found FluMist to be more effective than trivalent, inactive vaccine in children.