The hidden risk of a missing flu season

Science · Published 8 October 2026 Swipe more like this →

In short: During the 2020-2021 period, the world saw an unusual absence of influenza. While this may have seemed like a reprieve, it created a biological loophole that could impact public health today.

The lack of circulating flu viruses during the pandemic resulted in fewer people developing natural immunity to common seasonal illnesses. This phenomenon means a larger portion of the population may now be susceptible to infection as viruses begin to circulate more freely again.

Experts initially feared a "twindemic" where both COVID-19 and influenza would surge simultaneously in 2020-2021. Because that scenario did not materialize, the resulting gap in community immunity presents a potential challenge for future respiratory virus management.

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