U of M study: Flu shots fall short of 'consistent' high-level protection

ST. PAUL

The message to the general public remains: Get your flu shot.

But a new report from University of Minnesota researchers suggests that manufacturers of flu vaccines must work to improve their effectiveness.

Released Tuesday, the new review looked at more than 5,700 reports on influenza published over the past three decades and identified 31 studies that researchers say provide the best evidence on the effectivenss of flu vaccines.

Those studies suggest that existing vaccines have a "track record of substantial safety and moderate efficacy," researchers wrote, but fall short of the "consistent high-level protection" that's needed.

The findings should serve as a wake-up call for vaccine manufacturers, said Dr. Michael Osterholm of the U's Center for Infectious Disease Research and Policy.

"We need better vaccines," said Osterholm, who led the new study. "The current vaccines are acceptable today, but they're not acceptable for tomorrow."

Public health officials who reviewed the report agreed with the call for better vaccines. But they stressed that patients shouldn't lose faith in current vaccines -- particularly now, at the start of flu season.

"It's like with any product -- there may be something wonderful coming, but you're not going to throw away what you have until that new product comes along," said Kristen Ehresmann, an epidemiologist with the Minnesota Department of Health. "We will continue to use those existing tools."

The study is being published in the November edition of the Lancet Infectious Disease, a medical journal that went online Tuesday. It was written by Osterholm and colleagues at the U, the Marshfield Clinic Research Foundation in Wisconsin and Johns Hopkins University.

Two types of flu vaccines are used in the United States: injections of trivalent inactivated vaccine and a newer live attenuated influenza vaccine that's administered with a nasal spray.

The review found that flu shots were effective in preventing influenza in eight of 12 seasons and over the years had a combined efficacy of 59 percent against influenza in healthy adults.

But Osterholm said previous reports have suggested that flu shots are much more effective -- in the range of 70 percent to 90 percent.

The nasal spray vaccine was shown to provide significant protection in nine of 12 seasons against infections and had a combined efficacy in that period of 83 percent against influenza in children aged 6 months to 7 years.

But no study of the nasal spray vaccine showed significant protection in healthy adults 59 years old or younger, the study found.

Representatives of vaccine manufacturers, including GlaxoSmithKline and MedImmune, said they could not comment on the study because they hadn't yet reviewed it.

Tom Skinner, a spokesman for the federal Centers for Disease Control and Prevention, said the report's findings on the effectiveness of different vaccines are less important than the broad message.

"This study is a further testament to the need for us to have better vaccines available, and we need to continue to work on developing better vaccines," Skinner said.

"But in the meantime, we need to make sure people continue to get vaccinated using the vaccines that we do have."

Osterholm said researchers "still support the public health program to get people vaccinated." That includes both types of flu vaccines -- at least for certain groups.

The new review is important, Osterholm said, because the methodology of many past studies has led people to overstate the effectiveness of current flu vaccines. That, in turn, has made investors reluctant, Osterholm said, to fund startup companies trying to develop innovative flu vaccines.

"The ongoing public health burden caused by seasonal influenza and the potential global effect of a severe pandemic suggests an urgent need for a new generation of more highly effective and cross-protective vaccines that can be manufactured rapidly," the study authors wrote.

The "holy grail" for flu vaccines would be a product that could be given once and would provide protection against all flu strains for many years, said Ehresmann of the Minnesota Department of Health. Currently, flu vaccines are given every year and are designed to fight the viral strains that experts think will be circulating.

This year, the evidence suggests this season's flu vaccine is a good match for the strains that are circulating, Ehresmann said. This month, Minnesota recorded its first case of influenza for the 2011-12 season in a 26-year-old woman from Olmsted County.

"Wisconsin has just identified their first case, too, so it appears that the season is starting early," Ehresmann said. "That doesn't necessarily portend a bad season, but it's an excellent reminder for people to make sure they get vaccinated."

Distributed by MCT Information Services