THURSDAY, Dec. 11, 2014 (HealthDay News) -- Fewer than half of Americans have gotten a flu shot so far this flu season, which might be a bad sign for a season that could be potentially severe, infectious-disease experts said Thursday.
Worse, some people are thinking about skipping this year's flu shot, based on reports that the vaccine could provide only partial protection against what has been the predominant influenza strain this season, doctors said.
"That's a big concern," said Dr. Jeffrey Duchin, chief of the Communicable Disease Epidemiology and Immunization Section at Public Health -- Seattle and King County, Washington state. "We've had many people report that they've heard the vaccine isn't effective so they aren't going to bother this year, or they're questioning if they should bother."
Only 39.7 percent of adults and 42 percent of children had received their flu shots through mid-November, according to a telephone survey conducted by the U.S. Centers for Disease Control and Prevention.
Those numbers are comparable with vaccination rates last year at this time, the CDC reported.
"It's encouraging at least to see we are tracking with last year," said Duchin, who also is a professor of infectious diseases at the University of Washington. "But we should strive to do better this year. Since this is anticipated to be a severe year, it would be nice to see an increase in the number of people who get vaccinated."
Health-care workers may face an uphill battle promoting the flu vaccine, however, since word is spreading that this year's vaccine is only partially effective.
The CDC warned last week that a strain of influenza called H3N2 appears to be circulating most widely early this season, and that about half of the H3N2 viruses detected by researchers so far appear to have mutated. The mutation means that this year's flu vaccine will likely provide only partial protection against H3N2.
Flu seasons that feature widespread H3N2 infections tend to be nasty affairs. H3N2 viruses were predominant during the 2012-13, 2007-08 and 2003-04 flu seasons -- the three seasons with the highest death rates in the past decade, CDC officials noted. In the past, death rates from H3N2 have been more than double that of other flu strains.
Infectious-disease doctors and CDC officials are urging people to get their flu shot even though it may not be as effective against the mutated H3N2 strain.
"Even the partial protection is worth it because of the number of deaths and number of hospitalizations that can occur from H3N2," said Dr. Carolyn Bridges, associate director of adult immunizations at the CDC's National Center for Immunization and Respiratory Diseases.
Bridges added that this year's vaccine also provides full protection against two or three other strains of influenza that could circulate and become more widespread as the flu season progresses.
It may be unlikely that vaccination numbers will move much past where they are now, particularly for adults. By the end of last year's season, only 42 percent of adults and 59 percent of children had received a flu shot, according to the CDC.
There is one bright spot in the CDC's vaccination numbers -- a significant uptick in the number of pregnant women who are getting a flu shot.
As of early November, 43.5 percent of expecting mothers had received a flu shot, the CDC found. "Not too many years ago, we had vaccination rates in pregnant women that were routinely less than 20 percent," Bridges said.
Vaccination provides crucial protection for babies born during the flu season, Bridges and Duchin said.
"By vaccinating the mom, she produces antibodies that are passed on to her newborn," Duchin said. "That will protect that baby for up to six months. This is a really great thing to do to protect a baby during its first weeks of life, if it is born during flu season."
This year's flu season appears to be progressing as predicted, with most regions of the country showing elevated signs of flu symptoms, according to CDC figures for the week ending Nov. 29.
"We are seeing an increase in flu activity, so we want to see people get vaccinated as soon as they can before they are exposed to influenza in their community," Bridges said.
For more influenza, visit the U.S. National Institutes of Health.