How Much Time Should You Wait Before Second COVID Vaccine Dose?

While planning when to receive the COVID-19 vaccine, remember Pfizer-BioNTech and Moderna shots require different lengths of time between doses.

According to the Centers for Disease Control and Prevention, second shots should be administered as close to the recommended interval as possible, but can be given up to 42 days after the first dose, if necessary.

Here's when to receive the second dose:

• The second Pfizer dose should be given 21 days after your first dose
• The second Moderna vaccine dose should be given 28 days later

Though the CDC says second doses should not be administered earlier than the recommended interval, those given "within a grace period of 4 days earlier than the recommended date for the second dose are still considered valid."

Health care providers will likely schedule the second vaccine dose during the first dose appointment, typically with the option of picking another location, if necessary.

A new CDC study reported that a single dose of Pfizer's or Moderna's COVID vaccine was 80% effective in preventing infections. That number jumped to 90% two weeks after the second dose, the study on vaccinated health care workers showed.

Complete vaccination is said to be two weeks after a person receives their second dose of the two-shot Pfizer and Moderna vaccines, according to health officials.

If side effects persist after either dose of the vaccine, the CDC recommends people take over-the-counter medicines like ibuprofen, acetaminophen, aspirin or antihistamines, after speaking with a doctor.

The CDC does not recommend, however, that people take such over-the-counter medications or antihistamines to prevent side effects prior to receiving the coronavirus vaccine.

Health officials noted that it is not known how those medications might affect the efficacy of the vaccine. For people who take medications for underlying medical conditions, the CDC recommends to continue taking.