News

Some seniors who get flu shots may not be much better protected against the virus or related illnesses than those who go without, according to a new study that is creating fresh controversy over the effectiveness of immunization.

New questions are being raised after researchers in Seattle discovered vaccinated seniors were just as likely to develop pneumonia, a common and sometimes deadly complication of the flu, as other elderly people who didn't get shots.

"Basically, it's been taken for granted for a decade that this vaccine is effective in all seniors," said Michael Jackson, lead author of the study, published today in The Lancet, and former postdoctoral fellow at Seattle's Group Health Center for Health Studies. "We're starting to find out maybe that's not the case."

Researchers studied more than 3,500 seniors between 65 and 94 over the course of three flu seasons to determine whether flu vaccines offer a significant layer of protection against illness.

They determined that vaccination failed to significantly reduce the incidence of pneumonia, suggesting the benefit of flu shots among some groups of seniors may be more limited than previously believed.

"It does suggest we're not achieving the public health benefit of the influenza vaccine that has been suggested by prior studies," said Lisa Jackson, a senior investigator at the Group Health Center for Health Studies. "It certainly suggests there's room for improvement."

Since it's difficult to conduct a complete and accurate analysis based only using seniors who had the flu, as many cases are never reported, researchers looked at the incidence of pneumonia, a common illness that often results from flu complications, among seniors during flu season.

Previous studies have found that flu vaccines are associated with a 20- to 30-per-cent decrease in the incidence of pneumonia among seniors during flu season.

But Michael Jackson, now an epidemiologist at the U.S. Centers for Disease Control and Prevention, said those findings could have been exaggerated or biased as the result of flaws in the way the studies were designed.

In this study, researchers controlled for potential variables that could skew results, such as smoking history or frailty. None of the individuals involved lived in a nursing home or had a compromised immune system.

Dr. Jackson cautioned against interpreting the study as a sign that immunizations don't work. Rather, the findings highlight the need to explore potential alternatives for some seniors who may not benefit from the flu shot. For instance, it may benefit some seniors to use a higher dose vaccine or try a different formulation in order to improve its odds of working, he said.

But it's also important to keep in mind there is no vaccine that provides a fail-safe guarantee against illness or disease, said Ian Gemmill, former chair of the Canadian Coalition for Immunization Awareness and Promotion and medical officer of health for Kingston, Frontenac and Lennox and Addington Public Health.

While it may be time to explore how the flu shot can be improved to better help senior citizens, the vaccines serve an important purpose despite their shortcomings, he said.

"I wish it were a perfect vaccine, but it isn't," Dr. Gemmill said. "It's the best we've got now."