> These vaccines were invented a year ago A single scientist at Pfizer created 10 vaccine candidates in a day. Most worked, but some were less 'tolerated' than

> These vaccines were invented a year ago A single scientist at Pfizer created 10 vaccine candidates in a day. Most worked, but some were less 'tolerated' than others. It's ok to do that in a lab setting, with health care standing by. There are limited resources for trials, you can't easily scale to millions.