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CDC says second COVID-19 vaccine dose is important, but timing doesn't have to be exact

Covid19 Vaccine
Posted at 10:18 AM, Jan 27, 2021
and last updated 2021-01-27 15:29:20-05

SOUTHERN COLORADO — If you're worried about getting your second dose of the Pfizer or Moderna vaccine because of unexpected delays, the Centers for Disease Control and Prevention says the timing of the second dose doesn't have to be exact. Experts say you should still plan to get the second dose, though.

For the Pfizer vaccine, the booster comes three weeks (21 days) after vaccine administration. The Moderna vaccine requires the second dose four weeks (28 days) after inoculation.

However, the CDC says if you can't make the appointment in that recommended time frame, you will be fine as long as you get that second shot within 6 weeks (or 42 days) from getting the first one.

Here is the full written recommendation from the CDC's website:

"Persons should not be scheduled to receive the second dose earlier than recommended (i.e., 3 weeks [Pfizer-BioNTech] or 1 month [Moderna]). However, second doses administered within a grace period of 4 days earlier than the recommended date for the second dose are still considered valid. Doses inadvertently administered earlier than the grace period should not be repeated.
The second dose should be administered as close to the recommended interval as possible. However, if it is not feasible to adhere to the recommended interval, the second dose of Pfizer-BioNTech and Moderna COVID-19 vaccines may be scheduled for administration up to 6 weeks (42 days) after the first dose. There are currently limited data on efficacy of mRNA COVID-19 vaccines administered beyond this window. If the second dose is administered beyond these intervals, there is no need to restart the series."

Data has shown that the two vaccines are at least 94% effective after the second dose is administered. So far, there is not enough data to estimate the effectiveness of a single dose, leaders from the Federal Drug Administration said earlier this month.

"Your immune system is very smart," said NBC Senior Medical Correspondent John Torres. "It will remember receiving the initial dose. So, the bottom line is to get fully vaccinated in order to have all the protection you can against the virus." Torres explained you still want to try and get the shot as close to the recommended time frame as you can, and do not let a delay stop you from getting a second shot altogether.