How quickly do I need a second
COVID-19 vaccine shot?
By The Associated Press
January 13, 2021
How quickly do I need a second COVID-19 vaccine shot?
The first COVID-19 vaccines in the U.S. require two doses a
few weeks apart.
People should get some degree of protection within two weeks
of the first shot, with the second shot bringing about the
vaccineís full protection. For the vaccine by Pfizer and
Germanyís BioNTech, the second shot is supposed to be after
three weeks. For Moderna, itís four weeks.
But how closely those guidelines should be followed has been
a point of difference for the United States and the United
Kingdom, which has been rolling out the Pfizer vaccine and one
by Astrazeneca that requires two doses given four weeks apart.
To get more first shots into people and give them at least
some degree of protection, the U.K. says itís OK to delay the
boosters for as long as 12 weeks. But that strategy has been
nixed in the U.S., where regulators say thereís no science
backing the approach.
A major concern is that itís unknown how long the partial
protection from one dose can last. "There is no data to
demonstrate that protection after the first dose is sustained
after 21 days," Pfizer said.
U.S. regulators agreed, saying too few people in the Pfizer
and Moderna vaccine studies missed their scheduled boosters to
have enough data to show the strategy might work.
The timing of the shots doesnít have to be exact in the U.S.,
though; the Centers for Disease Control and Prevention says the
second shots can be given up to four days earlier or later.