School influenza vaccinations best strategy for slowing flu transmission

Jan 25 2005

The best strategy for minimizing future influenza morbidity and mortality would be to concentrate vaccinations in school children and high-risk groups, according to a new research commentary by scientists at Emory University.

The alternative vaccine plan is based on mathematical models developed by Ira Longini, PhD, and Elizabeth Halloran, MD, DSc, professors of biostatistics in Emory's Rollins School of Public Health, and on influenza field studies. The report will be published in the February 15 issue of The American Journal of Epidemiology.

The mathematical models show that vaccinating about 70 percent of school children, ages 6 to 18, with influenza vaccine would reduce community-wide transmission to very low levels. School children are the population group generally most responsible for transmission of influenza because of more exposure potential and less prior immunity than adults. Even if only 50 percent of school children could be vaccinated, this would still result in a considerable reduction in transmission within the community, according to the models. The vaccine strategy over the last several years has been based on distributing vaccine primarily to high-risk groups, and such a strategy has not been very effective in reducing influenza deaths and illness, the researchers assert. Due to the current vaccine shortage, this same strategy has been enacted with the further stipulation that vaccine be limited to high risk and other predefined groups, but not to low risk school children.

The researchers suggest that the alternative strategy of vaccinating children and high risk groups would require around 120 million doses of vaccine per season, taking into account the fact that many high-risk people are never vaccinated. They recommend that the federal government guarantee the purchase and distribution of that many doses of vaccine each year in order to stabilize production. This strategy not only would be effective for normal yearly flu outbreaks, but also for years of pandemic influenza when supplies of vaccine are more limited.

The Emory researchers cite several field studies by other research groups showing that mass vaccination of children can be effective in reducing influenza transmission in an entire community.

"Many influenza researchers have believed for decades that vaccinating school children would be an important indirect way to reduce influenza transmission," Dr. Longini says. "This strategy has never been carried out in the US, however, possibly because public health officials have until now mostly considered the direct protective effects of vaccination, and school children are not considered a high-risk group."

The Emory researchers suggest it would be important to evaluate such a strategy carefully. One option would be to mass vaccinate school children in several states, with other states used as comparisons. "The current vaccine shortage gives public health officials the opportunity to reconsider what we believe is a very important alternative strategy of vaccinating school children in addition to high-risk groups," Dr. Halloran says. "If this strategy were adopted, the incidence of influenza could be monitored in states that adopted the strategy and those that did not."