If I’ve gotten the first dose of the Moderna or Pfizer vaccine is there any flexibility in the 21 or 28 day waiting period to receive the second dose? And, if I missed the time window do I have to start all over again?

Timing of Your Second Shot

The timing between your first and second shots depends on which vaccine you received.

If you received the Pfizer-BioNTech COVID-19 Vaccine, you should get your second shot 3 weeks (or 21 days) after your first.

If you received the Moderna COVID-19 Vaccine, you should get your second shot 4 weeks (or 28 days) after your first.

You should get your second shot as close to the recommended 3-week or 4-week interval as possible. However, your second dose may be given up to 6 weeks (42 days) after the first dose, if necessary. You should not get the second dose early. ‚ÄčThere is currently limited information on the effectiveness of receiving your second shot earlier than recommended or later than 6 weeks after the first shot.

However, if you do receive your second shot of COVID-19 vaccine earlier or later than recommended, you do not have to restart the vaccine series. This guidance might be updated as more information becomes available.

Source: CDC