The Amazon city of Manaus may have achieved ‘herd immunity’: study

The Brazilian city of Manaus, which was devastated by the coronavirus pandemic, may have suffered so many infections that its population now benefits from “herd immunity,” according to a preliminary study.

Published on the medRxiv website, the study analyzed the infection data with mathematical models to estimate that 66 percent of the population had antibodies against the new coronavirus in Manaus, where the pace of the pandemic was as fast as it was brutal.

That may be high enough to have reached the threshold for herd immunity, in which enough members of a population are immune to a disease that can no longer spread effectively, said the study authors, a group of 34 Brazilian researchers. and international.

“The unusually high infection rate suggests that herd immunity played an important role in determining the size of the epidemic,” they wrote in the study, which has not yet undergone peer review.

“All evidence indicates that it was the very fact of being so exposed to the virus that caused the reduction in the number of new cases and deaths in Manaus,” he told the Sao Paulo State Research Support Foundation (Fapesp), who helped fund the study.

Located in the Amazon rainforest, Manaus was the scene of horrifying images of invaded hospitals, mass graves and corpses piled up in refrigerated trucks when the pandemic peaked in May.

But deaths in the city of 2.2 million people have dropped dramatically in recent weeks, to an average of just 3.6 per day for the past 14 days.

Manaus is now one of the fastest reopening cities since the shutdown in Brazil, the country with the second highest death toll in the world, after the United States, with nearly 139,000 dead.

That includes schools, businesses, nightlife, and its famous opera house.

However, health experts warned that trying to achieve herd immunity was a dangerous path for policy makers.

“Community immunity through natural infections is not a strategy, it is a sign that a government failed to control an outbreak and is paying for it in lost lives,” tweeted Florian Krammer, professor of microbiology at the Icahn School of Medicine. Mount Sinai Hospital in New York.

Other experts cautioned that immunity to the virus can be short-lived.

Manaus has registered 2,462 deaths from COVID-19.

If it were a country, it would have the second highest death rate in the world, with 100.7 deaths per 100,000 inhabitants.

© 2020 AFP