Single Dose of H1N1 Vaccine Highly Effective in Young

Study finds adjusted effectiveness was 93 percent overall in Canada in 2009

FRIDAY, Feb. 4 (HealthDay News) -- A single dose of H1N1 vaccine administered during the fall of 2009 in Canada appears to have been more than 90 percent effective in protecting recipients, particularly children and young adults, from the pandemic, according to research published online Feb. 3 in BMJ.

Danuta M. Skowronski, M.D., of the British Columbia Centre for Disease Control in Vancouver, Canada, and colleagues analyzed 552 patients with influenza-like illness between November and December 2009 to assess the effectiveness of the influenza A/H1N1 vaccine used in Canada during the fall of 2009. More than 80 percent of study participants were children and adults younger than 50 years of age.

The researchers note that the pandemic H1N1 virus was detected in 209 (38 percent) of patients, with 40 percent of the cases occurring in children and young adults and 9 percent occurring in adults 65 and older. One percent of the cases had received H1N1 vaccine, compared with 17 percent of controls -- all a single dose. The vaccine's adjusted effectiveness overall was 93 percent.

"Although limited by a small number of vaccine failures, this study suggests that the monovalent AS03 adjuvanted vaccine used in Canada during autumn 2009 was highly effective in preventing medically attended, laboratory confirmed pandemic H1N1 illness, with reference in particular to a single dose in children and young adults," the authors write.

Three authors disclosed financial relationships with pharmaceutical companies.

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