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Oct 25, 2011 (CIDRAP News) – Reacting today to a new analysis that shows gaps in the evidence for the benefits of influenza vaccines, several public health groups said the vaccine is still the best flu prevention tool, but its limitations should be acknowledged.
Several public health and medical organizations were contacted by CIDRAP News for comments on a meta-analysis that was released today by Lancet Infectious Diseases (see related story). After sifting through thousands of studies to find the most reliable ones, researchers concluded that flu vaccines can provide moderate protection from flu, but the benefits are much lower in some groups and in some seasons.
For adults aged 18 to 65, they found an overall vaccine efficacy, based on randomized controlled trials (RCTs), of 59%. But they found little evidence of vaccine efficacy or effectiveness in seniors (65 and older). In contrast, there was good evidence for the benefits of the live attenuated vaccine (LAIV) in children 6 months to 7 years old, but little support for its benefits in older children or adults.
The authors of the study, including two from the University of Minnesota Center for Infectious Disease Research and Policy, publisher of CIDRAP News, say the use of current vaccines must continue, but better vaccines are needed.
The same points were stressed today by Dr. Joe Bresee, chief of the epidemiology and prevention branch in the influenza division of the Centers for Disease Control and Prevention (CDC). Some CDC officials and other groups were briefed about the study yesterday via conference calls and webinars.
"I think the main conclusions of this review paper are significantly the same as other recent reviews," he said. "First, the flu vaccine works, and it's an important tool. Second, there's a lot of room for improvement."
Bresee said he didn't find the conclusions surprising. "I think the authors have done a nice service in putting all the findings together in one place. But it isn't surprising to us."
Noting that the authors found no RCT evidence for vaccine efficacy in seniors, Bresee commented that the finding "is an artifact of the fact that we've been recommending the vaccine [for those over 65] for several decades," making it unethical to conduct RCTs in that age-group. He said that while some observational studies of flu vaccine effectiveness in the elderly have been poor, others have shown substantial benefits.
At the Association of State and Territorial Health Officials (ASTHO), Jim Blumenstock, chief program officer for public health practice, said that while the study raises questions, the general message is that the flu vaccine is still effective for the majority of people who receive it.
"It just reinforces the fact that the vaccine has never been touted as a magic bullet that will protect everyone against flu," Blumenstock said.
"While it's a key weapon, it's not the only weapon," he added, noting that measures like good infection control practices in healthcare settings and general hygiene are important as well.
Paul Etkind, senior director of infectious diseases at the National Association of County and City Health Officials (NACCHO), said he was impressed by the comprehensiveness of the meta-analysis, which looked at studies as far back as 1967. He said the overall findings came "as kind of a surprise" to him.
He said the vaccine is not a "bad vaccine," but 59% or 60% efficacy is much lower than the 90% levels typical of childhood vaccines such as measles.
"I'm proud to be part of a profession that's always looking at things critically and looking at things that we have long accepted," Etkind said. "Certainly no one will argue that we don't need a better vaccine for flu."
Dr. William Schaffner, speaking for the Infectious Diseases Society of America (IDSA), said the authors of the study set "a very high bar" in their effort to include only the best studies. "There are many other studies that we all recognize don't have the high quality, but in the minds of many have good information and tend to fill in some of the gaps," he said.
Schaffner, who is a former IDSA board member and heads the department of preventive medicine at Vanderbilt University, said the overall findings won't come as news to anyone who has studied influenza vaccines thoroughly. He expects the study will raise questions about how much is known about flu vaccines and will help make the case for developing better ones.
One possibility mentioned in the report—that of recommending LAIV over TIV for young children, based on the evidence for greater LAIV efficacy—is on this year's agenda of the influenza working group of the Advisory Committee on Immunization Practices, Schaffner said.
He said the data supporting use of LAIV in young children have been accumulating, and he is convinced that it's the better vaccine for them. "The ACIP has been reluctant to express a preference when there are comparable products," he said, adding that the reasons can include uncertainty about the supply of a preferred vaccine.
The ACIP is scheduled to discuss flu vaccines in its meeting tomorrow.
The experts expressed some concern about the possible impact of the new findings on public attitudes, while agreeing that public health groups have to be open about the limitations of flu vaccines.
"The worst thing that could happen would be if folks in the community open their newspaper tomorrow and in their own mind hear that the vaccine is not effective and therefore think, 'Why should I go and get it?'" said Blumenstock.
Bresee said he doesn't see a need to change the public messages about flu vaccines in light of the new analysis: "From the CDC standpoint, the core message is still the same: that vaccines are still the best tools to prevent fu, but we need to make them better."
Etkind said public health groups need to continue encouraging people to get vaccinated, but added, "I think we have to adjust the use of our numbers. This is the best data available, and it's telling us the numbers are changing. . . . If we go into the specifics of it, we have to acknowledge that the numbers are lower than what we've been talking about."
He predicted that some groups, particularly anti-vaccine groups, will probably "paint the results in the worst possible light." But his advice is, "Let's be honest about it and deal with it. It's still a good vaccine and it's [vaccination] still a good thing to do."
Osterholm MT, Kelley NS, Sommer A, et al. Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis. Lancet Infect Dis 2011 (published online Oct 25) [Abstract]