Will Population (Herd) Immunity To Covid-19 Be Permanent Or Seasonal?

In just three weeks, the number of Covid-19 cases in the United States has plummeted by 35 percent. Death rates have yet to follow suit, but they have leveled out, with hospitalization rates on the decline, too. Given that the vaccine rollout is still proceeding slowly, the ebb is the glimmer of hope we need as we start to emerge from a long, dark winter. But is this really the light at the end of the tunnel, or just a period of calm before yet another storm?

There are two possible expirations for the sudden decrease. Americans, whether chastened by the holiday surges or influenced by the new administration, may be embracing safety measures like mask-wearing and social distancing. But it could be that population immunity, also known as herd immunity, is on the horizon. While confirmed case counts hover around 26 million, a study recently published in JAMA suggests the actual number is likely four times as high, around 100 million. Between the 100 million Americans who have contracted the virus and the 24 million vaccinated so far, we may be in the early phase of a steady decline. Similarly, India reached peak infection in mid-September 2020, a time when an estimated one third of the population has been infected. Since then new cases have been on a steady decline from a high of 100,000 per day to roughly 12,000.

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Originally published on Forbes (February 1, 2021)

© William A. Haseltine, PhD. All Rights Reserved.