Early estimates suggest that the flu vaccine performed unusually well in a U.S. winter flu season that already has dissipated.
The vaccine was more than 40% effective in preventing adults from getting sick enough from the flu that they had to go to a doctor’s office, clinic or hospital, health officials said during a Centers for Disease Control and Prevention vaccines meeting. Officials generally are pleased if a flu vaccine is 40% to 60% effective.
But one expert at the meeting was underwhelmed and said it points up the need for better flu vaccines.
“It is still disappointing” that the vaccine was a good match and yet effectiveness was still modest, said Dr. Sarah Long of Drexel University.
Yearly flu vaccinations are recommended for everyone 6 months and older. About half of eligible kids and just under half of adults got flu shots in the past several months, according to CDC data. Vaccination rates were up compared with 2021-2022 but below what they were before the COVID-19 pandemic hit in 2020, according to the CDC’s Brendan Flannery.
Influenza took off in early November as COVID and a respiratory virus called RSV roiled emergency departments. Among kids, flu-related hospitalization rates in November and December were as high as any in recent years, Flannery said. At least 111 flu deaths have been reported among children, the most since the 199 in the 2019-2020 season.
The dominant flu strain was the kind typically associated with higher rates of hospitalizations and deaths, particularly among older people. In some years, the vaccines were virtually ineffective against that strain in people 65 and older. But this season’s vaccine has done unusually well, with the best results seen in at least 10 years, said Flannery, who is responsible for the CDC’s flu vaccine effectiveness data.
Flu apparently made a very early exit, with the virus declining since the end of November.
It’s not clear exactly why the wave crested so early, but flu seasons have been unusually mild or otherwise strange since the coronavirus pandemic began, Flannery said.
CDC officials caution that flu season might not be over — late winter or spring second surges aren’t uncommon.
Among CDC findings:
- The vaccine was 44% effective in preventing adults’ lab-confirmed flu visits to urgent care clinics and hospital emergency rooms and 39% effective for people 65 and older.
- It was 43% effective against flu-related hospitalizations of all adults and 35% against flu hospitalizations of seniors.
- Among kids, the vaccine was 68% effective in preventing illnesses severe enough to require hospitalization and 42% effective for visits to the emergency department.
