(CNN) The United States reached a grim milestone on Saturday: 1 in 1,000 Americans have died from Covid-19 since the nation's first reported infection in late January.
In an ideal world, a pandemic vaccine could be delivered in a single shot, so supplies could be stretched to cover a lot of people. It would trigger no side effect more significant than a sore arm. And it would be easy to ship and store.
Two new studies give encouraging evidence that having COVID-19 may offer some protection against future infections. Researchers found that people who made antibodies to the coronavirus were much less likely to test positive again for up to six months and maybe longer.
As countries in Europe rush to close their borders to the United Kingdom to prevent transmission of a new — and potentially more transmissible — variant of SARS-CoV-2, research has estimated the effect of international travel restrictions on COVID-19 spread earlier in the pandemic.
