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

Hospitals in the Brazilian Amazon are collapsing again under pressure to treat Covid-19 patients. This is the case despite the high rate of coronavirus infection in the Amazon during the first wave of the virus, and suggests that herd immunity through infection may be more difficult than previously thought.

Hospital beds are not available in Manaus, the capital of the Amazon. People line up to buy oxygen tanks from private suppliers to try to …