Endemicity. I think we may have to re-evaluate our expectations of endemicity for SARS-CoV-2. In temperate parts of the world, we think of seasonality as the phase-locking of incidence/transmission at one time of year, often the winter... 1/6
This is patterned from our experience with influenza. The 4 well-documented flu pandemics emerged, produced a succession of waves over the first 2 years, then settled into a pattern of seasonal, one-outbreak-per-year endemicity. At population scales,... 2/6
...partial protection conferred from prior infection (and vaccination) keeps incidence and severe disease at levels lower than seen during the pandemic waves. Influenza is not alone; other respiratory viruses are seasonal, too, including the ‘endemic’ coronaviruses... 3/6
...(OC43, HKU1, 229E, NL63). But SARS-CoV-2 is different. It’s more aggressive. I don’t think we should expect it to devolve to a flu-like pattern. It has a much higher R0, evades immunity on shorter time scales, and is more virulent (jury still out on Omicron). 4/6
Given these properties, multiple outbreaks each year, such as we’ve seen during 2021, may be the norm for the foreseeable future. We may find ourselves in a different kind of endemic equilibrium in which boosting is needed every 4-6 months... 5/6
...and highly effective therapeutics are needed to limit severe disease. All this would need to be available globally and equitably. This is a daunting prospect. And psychologically challenging. 6/6
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