• Thread by ShamanJeffrey on Thread Reader App – Thread Reader App

    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.

    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, 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 (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).

    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 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.

    #endémie #Covid-19