A new report claims that 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.

The investigators were working on the premise that 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.

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 New England Journal of Medicine March 22, 2001; 344: 889-896