The flu vaccine has been 68% effective at preventing hospitalizations in children but has been less protective for seniors this season, according to preliminary data released Wednesday by the Centers for Disease Control and Prevention (CDC).
The vaccine showed a 35% effectiveness at preventing hospitalization for seniors in one study and 42% effectiveness in another analysis.
For individuals with weak immune systems, the vaccine reduced the risk of hospitalization by 44% in one study and 30% in another.
The flu season hit early this year, with the weekly hospitalization rate peaking in December and declining since then, according to CDC data. Since October, the flu has caused 25 million illnesses, 280,000 hospitalizations, and 18,000 deaths, including more than 100 children.
Flu cases surged last fall after two years of low virus circulation due to the masking and social distancing measures implemented during the Covid-19 pandemic.
Dr. Jose Romero, head of the National Center for Immunization and Respiratory Disease, noted that the simultaneous circulation of Covid, flu, and respiratory syncytial virus (RSV) put significant pressure on hospitals and drug supply chains in the U.S.
“After a brief and anticipated uptick of hospitalizations and cases around the holidays, we are now seeing a continued decrease in Covid, influenza, and RSV cases and hospitalizations nationally,” Romero told the CDC’s independent advisory committee Wednesday.
“While influenza activity is declining, it remains possible that a second wave may occur later in the season as it has in the past,” Romero added.
Children and seniors are typically at the highest risk of severe disease from the flu. About 52% of children and 70% of seniors had received a flu vaccine as of late January, according to CDC data. The CDC recommends seasonal vaccination for everyone aged 6 months and older.
The effectiveness of flu vaccines can vary widely from season to season, depending on how well the strains included in the shots match the circulating viruses. Dr. Lisa Grohskopf, a CDC official, stated that the vaccines and circulating flu strains were reasonably well matched this season.
Hospitals were overwhelmed last fall by the simultaneous spread of Covid, flu, and RSV. The Children’s Hospital Association called on the Biden administration to declare a public health emergency in November, describing the surge in hospitalized children at that time as “alarming.”
While there are widely available Covid and flu shots, no vaccines exist for RSV. However, several companies are developing RSV vaccines for older adults that could receive Food and Drug Administration approval this year.
Pfizer is developing a vaccine that protects infants from RSV, and Sanofi has asked the FDA to approve an antibody called nirsevimab that also protects children up to two years old.
