Flu vaccine 55% effective in children this season, early estimates show
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The 2019-2020 influenza vaccine has been 45% effective overall in the United States this season and 55% effective in children, according to preliminary estimates published today in MMWR.
Based on data from more than 4,100 adults and children, vaccine effectiveness (VE) against any type of influenza was estimated to be 45% (95% CI, 36%-53%), including 50% against influenza B/Victoria viruses (95% CI, 39%-59%) and 37% against influenza A(H1N1) (95% CI, 19%-52%).
The season got off to an early and unusual start, with influenza B viruses predominating. B viruses are more common in children, and this season has been particularly tough on school-age kids.
Overall, there have been 26 million to 36 million illnesses and 12 million to 17 million medical visits attributed to influenza in the U.S. this season, according to CDC estimates. The agency estimates that there have been 250,000 to 440,000 hospitalizations and 14,000 to 36,000 deaths related to influenza this season.
As of Feb. 8, there were 92 reported influenza-related pediatric deaths attributed to influenza. Other than the 2009 pandemic, this is the largest number recorded at this point in the season since reporting began during the 2004-2005 season, according to the authors of the MMWR report.
The VE estimates were consistent with those from previous seasons, which ranged from 40% to 60% when influenza vaccines were antigenically matched to circulating viruses, the authors noted.
The rate of outpatient visits attributed to influenza first exceeded the national baseline during the week ending Nov. 9 — signaling the earliest start to an influenza season in more than a decade, the authors said.
After an executive order was issued by the White House on Sept. 19, the CDC, NIH, FDA and the Biomedical Advanced Research and Development Authority began collaborating to improve the effectiveness of influenza vaccines. – by Ken Downey Jr.
Disclosures: The authors report no relevant financial disclosures.
Perspective
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Bernhard L. Wiedermann, MD, MA
I was reasonably pleased that there were no hints of poor efficacy, particularly in children. The numbers are similar to what we’ve seen in past years, though this year was very different in that we’ve had a slightly earlier influenza season and most importantly a predominance of influenza B strains. Of course, what they can’t tell us is how well the vaccines worked at preventing hospitalization and more serious outcomes, but I suspect we are seeing benefit there as well. We’ll get more numbers in late summer, after they have had a chance to crunch the numbers at the end of the influenza season, that will provide more accurate estimates of efficacy. Those numbers are usually a little different from the interim results.
Although we’re on the front lines and still in the midst of a busy influenza season, it’s really impossible for me to have even an educated guess about vaccine efficacy locally. We just don’t have the number of patients to allow me to draw my own conclusions.
The bottom line for the public is we are still in the midst of a very busy influenza season. It is not too late to immunize yourself and your children, so please do so now. These numbers support the conclusion that there is a significant benefit from this year’s influenza vaccines. And of course, always practice good hygiene by not going to work when sick, not sending children to school when they are sick, covering your mouth and nose for coughing and sneezing, and washing your hands!
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