Two European patients were confirmed to have been re-infected with the coronavirus, raising concerns about people’s immunity to the virus as the world struggles to tame the pandemic.

Researchers at the University of California, San Francisco (UCSF) synthesized a molecule inspired by llama antibodies called nanobodies that could neutralize SARS-CoV-2, the virus that causes Covid-19.

Global coronavirus cases pushed past 20 million, according to a Reuters tally, with the United States, Brazil and India accounting for more than half of all known infections.

Johnson & Johnson kicked off U.S. human safety trials for a Covid-19 vaccine after releasing details of a study in monkeys that showed the company’s best-performing vaccine candidate offered strong protection in a single dose.

Unlisted German biotech firm CureVac will become the second company after rival BioNTech to launch human trials of an experimental coronavirus vaccine in the country, eyeing a potential approval in mid-2021.

Cancer patients with COVID-19 who were treated with a drug combination promoted by U.S. President Donald Trump to counter the coronavirus were three times more likely to die within 30 days than those who got either drug alone, U.S. researchers reported.

The novel coronavirus has killed more than 100,000 people in the United States, according to a Reuters tally, even as the slowdown in deaths encouraged businesses to reopen and Americans to emerge from more than two months of lockdowns.

France, Italy and Belgium acted to halt the use of hydroxychloroquine to treat patients suffering from COVID-19 amid questions about the safety of the generic anti-malaria drug.