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COVID-19 ISO Insights

Covid-19 Correlated with a Reduction in Flu Cases – Some Precautions to Remain?

June 21, 2021

By Travis Decaminada

Key Takeaway: Covid-19 precautions may have dramatically reduced the number of influenza infections over the past year, potentially causing some strains of the virus to go extinct. Government agencies suggest that some Covid-19 measures may continue during future flu seasons.

One of the few positive impacts of the Covid-19 pandemic: some strains of the influenza virus have reportedly gone extinct, per NPR. Even better, fewer strains of the flu virus may also lead to more effective vaccines. According to the article, in order to develop a flu vaccine scientists must “guess”, in a sense, which strains of the flu virus will be most active in a given flu season, if they’re wrong, the resulting vaccines may fail to properly immunize people. Per the article:

So what they have to do is sort of look within each class of viruses to see which strains are the most dominant. But they're doing it months in advance. Like, for our flu shot in the Northern Hemisphere, they're deciding in February what should go into the flu shot we're going to get the following autumn. So they have to look and see what seems to be dominant, what seems to be receding and make some choices. But it's been very hard in recent years, particularly with H3N2 viruses because they've been so diverse.

The implication being that fewer active flu viruses may make this decision easier for scientists going forward. Further, per CNBC, future flu vaccines and covid vaccines may be delivered at the same time, potentially reducing cases of the flu even further.

Covid and the Flu

The ISO Emerging Issues (EI) team wrote about the link between covid-19 and a reduction in influenza cases last year (here). Since then the Centers for Disease Control and Prevention (CDC) have also released their own report noting that influenza cases have been “historically low” in the United States, highlighting that positive test results have decreased from >20% to 2.3% over the past year. A reduction of more than 800%.

The CDC credits this decrease to the “community mitigation measures” put in place in an effort to combat Covid-19. Unsurprising given that Covid-19 reportedly spreads in a similar way to the influenza virus. Last August the EI team reported on the influenza virus spreading via fomites here. The CDC also notes that preventative measures put in place for Covid-19 may continue in the future. The immunocompromised and other high-risk groups in particular may benefit from adopting some Covid-19 protocols.

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