Protect and Defend

With the global number of confirmed cases at nearly 5 million and more than 300,000 deaths from COVID-19, much remains unknown about SARS-CoV-2, the virus that causes the disease. Two critical questions are whether vaccines will prevent COVID-19 and whether individuals who have recovered from COVID-19 are protected when they encounter the virus again.

https://hms.harvard.edu/news/protect-defend