This winter's flu vaccine is effective against the most common strain of the virus less than half the time, the U.S. Centers for Disease Control and Prevention announced Thursday.
It is largely ineffective for people ages 18 to 49, preventing serious flu cases only 21 percent of the time.
The vaccine, whose "recipe" is tweaked every year in anticipation of which strains will prove to be commonplace, protected people exposed to the flu 48 percent of the time.
However, there were stark differences depending the strain encountered:
- The vaccine is 73 percent effective against the B strain of flu. Unfortunately, that's not the strain affecting the most people this flu season.
- It is only 43 percent effective against the more prevalent strain, which is a certain version of Influenza A dubbed H3N2 because of its protein makeup. Nine out of ten flu sufferers this winter have this type of Influenza A.
- Overall, its effectiveness reached 48 percent.
"Forty-eight percent is not bad. It's actually pretty good," said Peter Wenger, a pediatric infectious diseases expert at St. Peter's University Hospital in New Brunswick. A really stellar vaccine year would see an effectiveness of about 60 percent, he said.
"Is it perfect? Absolutlely not. But it's good. If we waited for everything to be perfect, we wouldn't leave the house," he said.
Although the current vaccine includes protection against H3N2, the CDC said viruses in that category evolve so quickly and frequently it's hard for vaccine-makers to anticipate the changes. Scientists have identified nearly 600 variations of the virus this season.
Public health officials stress it still makes sense to get the vaccine, as people have roughly 50 percent chance it will prevent the illness or if not, at least turn a rough experience into a more mild case.
"Influenza activity is likely to continue for several more weeks in the United States, and vaccination efforts should continue as long as influenza virus are circulating," the CDC warned.
Wenger agreed. "Given that the risks of vaccination are not great, despite what some people say, sure, why not get the shot? It's not expensive, and it means you're much less likely to get the flu."
Flu activity in New Jersey remains high.
One piece of bright news within the CDC report was word the anti-viral medication that can be used to reduce the severity of a flu case remains effective against this winter's dominant strains.
That caused the CDC to advise doctors to consider using anti-viral medication on any older patients whose symptoms are flu-like - even for patients who said they got vaccinated. They also should not wait for formal lab reports to come back before prescribing anti-viral treatment, the guidance stated.
Kathleen O'Brien may be reached at kobrien@njadvancemedia.com. Follow her on Twitter @OBrienLedger. Find NJ.com on Facebook.
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