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By Suzanne Rostler
NEW YORK, Mar 21 (Reuters Health) - Vaccinating schoolchildren against influenza can reduce the number of elderly people who die from the virus and its complications each year, according to a report released Wednesday.
A mass influenza (flu) vaccination campaign in Japan between 1962 and 1987 prevented one death in the elderly for every 420 children vaccinated--resulting in 37,000 to 49,000 lives saved every year. At that time, very few elderly Japanese or others at high risk were given the vaccine, the strategy used in the US and other countries to prevent flu deaths.
However, vaccinating children in addition to the elderly could prevent more flu-related deaths than just vaccinating the elderly, whose immune systems may be too weak to ward off the virus, according to Dr. Thomas A. Reichert, the study's lead author.
Vaccinating the elderly only protects about half of those immunized. Targeting children creates what researchers call "herd immunity"--protection against infection that susceptible people get when most of the population is immune to a virus. This can substantially reduce the chances that a virus spreads.
"We see no other explanation other than herd immunity for the reduction in winter season mortality we described in Japan," said Reichert, from Becton Dickinson and Entropy Limited in Upper Saddle River, New Jersey.
Since relaxing the campaign, the incidence of flu and deaths from complications such as pneumonia have increased in Japan, according to the report in the March 22nd issue of The New England Journal of Medicine. Since 1997, Japan has recommended that the elderly and other high-risk individuals receive flu shots, which will allow researchers to determine which strategy is most effective.
Japan launched its previous campaign in the early 1960s, after a devastating flu epidemic was blamed for about 8,000 deaths over two seasons and led to widespread school closures. By the late 1980s, 50% to 85% of all Japanese schoolchildren had been immunized against influenza.
But lawsuits alleging adverse side effects and skepticism over the campaign's effectiveness caused the rate of vaccination to plummet and by 1994, Japan's program ended. Soon, the report indicates, flu-related deaths among the elderly began to climb.
After Japan launched the vaccination campaign, the rate of influenza-related death dropped to levels equal to those in the US despite an increase in the number of elderly people. Earlier, the rate of death from influenza in Japan was 3- to 4-times higher than in the US, the authors note.
"We hope it is clear that vaccinating schoolchildren against influenza reduces deaths due to a large variety of causes in the elderly," Reichert told Reuters Health. "This provides a new tool for the protection of societies against an ancient and deadly predator."
The findings are based on an analysis of the monthly rates of death between 1949 and 1998.
The research team included members from the pharmaceutical companies Becton Dickinson and Aventis Pasteur.
SOURCE: The New England Journal of Medicine 2001;344:889-896.
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