Covid-19 outbreak in Manaus suggests herd immunity may not be possible

New Scientist Default Image — Oxygen supplies have run out in hospitals in Manaus, Brazil, so people are buying cylinders from private companies to use at home

Hospitals in the Brazilian Amazon are collapsing once again under the strain of treating covid-19 patients. This is despite the high rate of coronavirus infections in Amazonas during the first wave of the virus, and suggests that if herd immunity by infection is possible, it may be harder to achieve than previously thought.

In Manaus, the capital of Amazonas, hospital beds are unavailable. People are queuing to buy oxygen tanks from private suppliers to attempt to …