COVID-19 vaccine hunt heats up globally, still no guarantee

Depending on how you count, there are between eight to 11 vaccine candidates in early stages of testing in China, the US, Britain and Germany — a collaboration between Pfizer Inc and BioNTech last week began a study in Germany that's simultaneously testing four somewhat different shots. More study sites are about to open in other countries — and between May and July another handful of different vaccines are set to begin first-in-human testing.