The false promise of herd immunity for COVID-19

The false promise of herd immunity for COVID-19

In May, the Brazilian city of Manaus was devastated by a large outbreak of COVID-19. Hospitals were overwhelmed and the city was digging new grave sites in the surrounding forest. But by August, something had shifted. Despite relaxing social-distancing requirements in early June, the city of 2 million people had reduced its number of excess deaths from around 120 per day to nearly zero.

In September, two groups of researchers posted preprints suggesting that Manaus’s late-summer slowdown in COVID-19 cases had happened, at least in part, because a large proportion of the community’s population had already been exposed to the virus and was now immune. Immunologist Ester Sabino at the University of São Paulo, Brazil, and her colleagues tested more than 6,000 samples from blood banks in Manaus for antibodies to SARS-CoV-2.

“We show that the number of people who got infected was really high — reaching 66% by the end of the first wave,” Sabino says. Her group concluded1 that this large infection rate meant that the number of people who were still vulnerable to the virus was too small to sustain new outbreaks — a phenomenon called herd immunity. Another group in Brazil reached similar conclusions.


3 thoughts on “The false promise of herd immunity for COVID-19

  1. Emma Talbot says:

    I think this is a startling fact, but we have to take it.

  2. Aadila Ghaffari says:

    Right now the higher margin fixed is at 90%. What would happen to the 10%?

    1. Lilly Cherian says:

      Well, Aadila, I appreciate your anxiety, but there is no way to save everybody — whichever way you look at it. Perhaps governments and researchers picthed in late, if not too late.

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