Researchers Believe Influenza Vaccines Need Improvement

Larry Hand

October 25, 2011

October 25, 2011 — Critical gaps exist in the evidence for the effectiveness of licensed influenza vaccines in the United States, researchers report in an article published online October 25 in The Lancet Infectious Diseases. Individuals who are at risk for medical complications or people who are aged 65 years or older are especially affected by the gaps, the researchers write.

The researchers conducted a meta-analysis of 31 studies that used laboratory tests to confirm influenza infections. These studies were selected from 5707 studies identified, published over a period of 40 years. The authors found that trivalent inactivated vaccine, which is used for 90% of influenza vaccinations in the United States, is only effective in preventing infection in 59% of healthy adults. They also found live attenuated influenza vaccine, which is not approved for adults who are aged 50 years or older, to be effective in 83% of children aged 7 years or younger, and in 69% of people younger than 65 years.

"The ongoing health burden caused by seasonal influenza and the potential global effect of a severe pandemic suggests an urgent need for a new generation of more highly effective and cross-protective vaccines that can be manufactured rapidly," write Michael Osterholm, PhD, MPH, from the University of Minnesota, Minneapolis, and lead author of the study, and colleagues. "In the meantime, we should maintain public support for present vaccines that are the best intervention available for seasonal influenza."

The researchers found no published papers on randomized controlled trials of trivalent inactivated vaccine efficacy in people aged 2 to 17 years or in adults aged 65 years and older. They also found no such trials for live attenuated influenza vaccine efficacy in people aged 8 to 59 years. In addition, they found "substantial variability" by season and age group.

Earlier research has shown vaccines to be from 70% to 90% effective in healthy adults if matched to the circulating strains. "The difference between 69% effectiveness and 90% effectiveness (or greater) will have a major public health effect in any pandemic that causes serious morbidity or increased mortality," the researchers write.

They recommend that industry and government form partnerships to accelerate research and reduce regulatory barriers to bring new vaccines already in development to market.

Lancet Infect Dis. Published online October 25, 2011.


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