In Brazil's Amazon a COVID-19 resurgence dashes herd immunity hopes - Reuters

BRASILIA (Reuters) - The largest city in Brazil’s Amazon has closed bars and river beaches to contain a fresh surge of coronavirus cases, a trend that may dash theories that Manaus was one of the world’s first places to reach collective, or herd, immunity.

University of Sao Paulo researchers suggested that a drastic fall in COVID-19 deaths in Manaus pointed to collective immunity at work, but they also believe that antibodies to the disease after infection may not last more than a few months.

The high infection rate suggested that herd immunity led to the dramatic drop in cases and deaths, the study said.

The study’s lead researcher, Ester Sabino, declined to be interviewed for this article because the Manaus herd immunity study awaits peer review for publication.

Almeida said too little is known about COVID-19 and whether re-infection is possible to verify if herd immunity was reached in Manaus, but some short-lived immunity probably had been attained.

“It’s a bit premature to speak of herd immunity from a new disease that we are still learning about, but we are seeing people with mild cases that appear to have anti-body immunity that can last for 2-3 months,” he said.

The Sao Paulo University study said coronavirus antibodies appeared to wane after just a few months, which could explain the resurgence in Manaus.