Four-year-old Gabriella Diaz sits as registered nurse Charlene Luxcin, right, administers a flu shot at the Whittier Street Health Center in Boston, Mass. The Centers for Disease Control and Prevention on Monday reported flu season is getting worse. Flu was widespread in 43 states and flu activity was intense in most of them, according to the latest national data for the week of Christmas.NEW YORK — As predicted, this year’s flu vaccine is doing a pretty crummy job. It’s only 23 percent effective, primarily because it doesn’t include the bug that is making most people sick, according to a government study released Thursday.
That’s one of the worst performances in the last decade, since U.S. health officials started routinely tracking how well vaccines work. In the best flu seasons, the vaccines were 50 to 60 percent effective.
“This is an uncommon year,” said Dr. Alicia Fry, a flu vaccine expert at the Atlanta-based Centers for Disease Control and Prevention, who was involved in the study.
The findings are not surprising. In early December, CDC officials warned the vaccine probably wouldn’t work very well because it isn’t well matched to a strain that’s been spreading widely.
Chattanooga is among communities that have been hit hard by the flu.
At the end of December, a flu index maintained by the pharmacy chain Walgreens ranked the city No. 1 in the nation for highest level of flu activity in a metro area, based on Tamiflu sales. The latest index shows Chattanooga still is in the top five metro areas nationwide.
Each year, the flu vaccine is reformulated, based on experts’ best guess at which three or four strains will be the biggest problem. Those decisions are usually made in February, months before the flu season, to give companies that make flu shots and nasal spray vaccine enough time to make enough doses.
But this year’s formula didn’t include the strain of H3N2 virus that ended up causing about two-thirds of the illnesses this winter. And that strain tends to cause more hospitalizations and deaths, particularly in the elderly, making this a particularly bad winter to have a problem with the flu vaccine.
Indeed, the flu season is shaping up to be a bad one. Health officials are comparing it to the nasty flu season two winters ago, and this one may prove to be worse. Hospitalization rates in people 65 and older are higher than they were at the same point in the 2012-2013 season, according to CDC data.
Hospitals in Chattanooga saw flu numbers surge in December. For the week ending Dec. 27, Erlanger’s emergency room recorded nearly triple the cases seen in any one-week period during the previous flu season. Parkridge saw its flu cases double in the last half of the same month.
Statewide in Tennessee, three children died of flu in December — the highest number reported for that month since the state’s health department began tracking them in 2007.
The study involved 2,321 people in five states — Michigan, Pennsylvania, Texas, Wisconsin and Washington — who had respiratory illnesses from November to early January. The researchers said vaccinated people had a 23 percent lower chance of winding up at the doctor with the flu.
CDC officials say people should still get a flu shot this year. Recently, the flu season in the U.S. has peaked in January or February, but people can continue to get sick for months. And they could get infected by the flu strains that were included in this year’s version.