Five questions you should be asking about Pfizer's coronavirus vaccine

Important scientific announcements are usually made through peer-reviewed medical research papers, not company press releases

Pfizer’s announcement on Monday that its Covid-19 shot appears to keep nine of 10 people from getting the disease sent its stock price rocketing. Many news reports described the vaccine as if it were our deliverance from the pandemic, even though few details were released.

There was certainly something to crow about: Pfizer’s vaccine consists of genetic material called mRNA encased in tiny particles that shuttle it into our cells. From there, it stimulates the immune system to make antibodies that protect against the virus. A similar strategy is employed in other leading Covid-19 vaccine candidates. If mRNA vaccines can protect