The federal government reported on Friday that this year’s influenza vaccine appears to be cutting the risk of getting sick by about 62 percent.
That rate is about on par with vaccine-effectiveness rates in recent years, the U.S. Centers for Disease Control and Prevention said in a weekly report describing epidemic levels of flu across the entire country.
The vaccine may not be perfect, but overall numbers show that it is working, the CDC and other experts said.
“It’s not a great vaccine in terms of preventing infection, or even mild to moderate symptoms,” said Paul A. Offit, a professor of vaccinology at the University of Pennsylvania. But, Dr. Offit said, “the goal is to keep people out of the hospital and out of the morgue, and I think this vaccine does that.”
Other researchers, however, have been sending a different message. A group led by Michael T. Osterholm, a professor of environmental health sciences at the University of Minnesota-Twin Cities, has been warning that the government still isn’t paying enough attention to the danger of flu, which kills an estimated 3,000 to 49,000 people in the United States each year.
Mr. Osterholm is director of the university’s Center for Infectious Disease Research and Policy, which issued a report in October describing government agencies and researchers as far too satisfied with current flu technologies.
As an example, he said, there are now 177 influenza vaccines in clinical trials worldwide, but only 13 involving technologies other than finding antigens to attack the head of the hemagglutinin, a substance on the surface of influenza viruses.
Of the 13 trying new approaches, Mr. Osterholm said, all rely on private or foreign financial support. “There’s no U.S.-government support for novel antigen vaccines in clinical trials right now,” he said.
CDC leaders, discussing their latest weekly report on the spread of the flu, acknowledged on Friday that there are shortfalls while emphasizing their commitment to find better options.
“What we’ve known for a long time is that the flu vaccine is far from perfect,” said Thomas R. Frieden, the CDC’s director. “But it’s still by far the best tool we have to prevent the flu.”
In its report, the CDC said the current vaccine was a match for all three of the most common strains of flu now circulating—known as H3N2, H1N1 (the “swine flu” that caused a pandemic in 2009), and a type of “B strain.”
One sign of the lack of basic knowledge about the flu, Mr. Osterholm said, is that the CDC data show the vaccine gave 55-percent protection against H3N2, the main strain of flu sickening people right now, but gave 70-percent protection against a B strain known as B/Victoria, even though B/Victoria wasn’t even in the vaccine. “Is that counterintuitive or what?” he said.
Also, while effectiveness is a measure of how many people get sick despite getting the vaccine, there’s been little effort to measure whether people who got the vaccine suffer a lower grade of severity, Mr. Osterholm said.
“The data is sparse on this,” said Joseph S. Bresee, chief of the Epidemiology and Prevention Branch of the CDC’s Influenza Division. Some data, however, suggest those who have been vaccinated suffer a milder form of flu, Dr. Bresee said.
Mr. Osterholm disagreed, saying the few studies on the subject, including one soon to be released, show vaccination produces no significant difference in the severity of symptoms.