TUESDAY, Nov. 2, 2004 (HealthDayNews) -- Getting a flu vaccine two or more years in a row offers more lifesaving protection for elderly people than a single shot does, a new Dutch study has found.
Unlike the United States, the Netherlands is not experiencing a flu vaccine shortage this year.
"In our study in community dwelling elderly people, those who received annual revaccination had a lower mortality risk compared to those who received the influenza vaccination for the first time," said Drs. Bruno Stricker and Bettie Voordouw, senior author and lead author, respectively, of a report in the Nov. 3 issue of the Journal of the American Medical Association. Stricker and Voordouw are both with Erasmus Medical Center in Rotterdam.
In other words, the vaccine has a cumulative effect.
"The vaccine is important. There is a benefit to having it on a consecutive yearly basis," agreed Dr. Brent Ridge, an assistant professor and director of clinical strategy at Brookdale Department of Geriatrics and Adult Development of Mount Sinai School of Medicine in New York City.
Older people, as well as those with chronic medical conditions, are more vulnerable to complications from influenza, such as pneumonia. Indeed, both of these groups remain on the U.S. Centers for Disease Control and Prevention's high-priority list, in line to receive this year's limited vaccine before others who are less vulnerable.
Annual revaccination has been proposed as a way to boost protection for the elderly but, so far, there had been no definitive data, the study authors said.
The new study used data on 26,071 people aged 65 or older from 1996 through 2002. Depending on the year, 64 percent to 74 percent of the group was vaccinated.
One flu shot was associated with a 10 percent reduction in the risk of death, which the study authors termed "non-significant." Revaccination -- defined as flu shots for at least two consecutive years -- reduced the risk of death by 24 percent. During epidemic periods, the additional reduced risk was 28 percent, the study found.
People aged 70 or older seemed to benefit the most from consecutive vaccinations.
Individuals who skipped a year had a 25 percent increase in mortality risk. But starting up again with an annual flu shot resulted in a renewed reduction in risk of death, the study found.
And therein lies the message for seniors who may have to miss the flu vaccine this year because of the shortage.
"Our biggest concern would be that people who don't get vaccinated this year and who don't get the flu will think they don't need the vaccine next year," Ridge said. For people who don't get the vaccine, not getting the flu should not lead to a false sense of security. Quite the contrary, picking up again with vaccinations even after skipping a year has a benefit, he said.
What accounts for the vaccine's cumulative effect?
"That is uncertain but it might be that the annual revaccination is important in maintaining an immunological memory against circulating influenza strains, especially in elderly individuals," Stricker and Voordouw said.
Dr. Michael Freedman is director of the division of geriatrics at New York University Medical Center in New York City. "Like anything else, if you keep getting injections every year, you're probably going to recruit different arms of the immune system so that you'll get a more vigorous response," he explained.
The authors would not comment on the advantage to healthy people who get revaccinated. "Our study does not address healthy people in general, but only those aged 65 years or older," they said. "Healthy elderly appeared to benefit from annual revaccination at least as well as those elderly in poorer health."
The bottom line, at least for elderly people: Get a flu shot every year, if you can find one.
U.S. health officials estimate there are approximately 63 million doses of injectable vaccine available this flu season, along with 3 million doses of nasal vaccine. That's still well short of the 100 million doses the federal government had expected before British authorities shut the manufacturing plant of a major supplier last month due to bacterial contamination.
For more on the flu and the current vaccine shortage, visit the U.S. Centers for Disease Control and Prevention.