How vaccine studies progress
Pfizer and BioNTech have enrolled nearly 44,000 people in testing their vaccine. As with any double-blind testing, neither volunteers, nor Pfizer and BioNTech know who gets the real vaccine and who gets the placebo. This is done to reduce the risk of the researchers or participants influencing the outcome of the testing.
SOURCES: Associated Press
Of the 44,000 enrolled, half are given a placebo and half are administered the vaccine.
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A second dose is
About three weeks later
The volunteers are monitored to see who develops symptoms or tests positive.
Independent observers examine how safe and effective the vaccine is.