This season’s flu vaccine is about 36 percent effective, the Centers for Disease Control and Prevention said in preliminary data published Thursday, with better results in children.
Health officials have said this season’s shot is less effective than in past years, but the numbers suggest it’s performing better than was initially feared.
The vaccine protects against three strains of flu. Two are type A strains, meaning they infect humans and animals: H3N2, the predominant strain circulating and H1N1. It also protects against an influenza B strain.
Effectiveness against H3N2 strains is typically lowest. The CDC estimated this year’s shot as 25 percent effective against H3N2, 67 percent against H1N1 and 42 percent against flu B.
For children 6 months to 8 years old, overall effectiveness was 59 percent.
Flu B tends to circulate toward the end of flu season, so the vaccine should provide better protection overall as B strains become more prevalent.
“This year’s vaccine protects against H3N2, but that strain of the virus is known to change frequently throughout the season, making the vaccine less effective against the virus. Protection is higher against other strains included in the vaccine and can help flu illness be milder and shorter for those who still get sick,” said Washington state’s communicable disease epidemiologist, Dr. Scott Lindquist, in a Department of Health news release.
The data is based on a survey of 4,562 U.S. adults and children from Nov. 2, 2017, to Feb. 3 who sought care at one of five sites around the country for an acute respiratory infection with a cough. The study collected demographic data about each patient, including vaccination status and noted whether they tested positive for the flu and if so, which strain they had.
Flu hospitalizations have decreased slightly in Spokane County after spiking in January. Last week, 22 new people were hospitalized with the flu, according to the Spokane Regional Health District’s weekly report, and three died. The Jan. 9 report counted 100 new hospitalizations and seven deaths.
The Department of Health said flu activity is expected to be high for several more weeks, and encouraged people who have not yet had a flu shot to do so.