SEATTLE — We often hear about health care facilities and residents waiting to receive second doses of the COVID-19 vaccine. But is there a difference between the first and second doses of the Pfizer and Moderna vaccines?
Pfizer and Moderna both reported their vaccines are roughly 95% effective in preventing the virus, but a person needs two shots to get that level of protection. While you need two doses for it to be fully effective, both the first and second doses of the Pfizer or Moderna COVID-19 vaccine are the same.
To verify, we looked at the original Pfizer and Moderna COVID-9 vaccine studies and consulted with Dr. Larry Corey, a nationally renowned vaccine expert at Seattle’s Fred Hutchinson Cancer Research Center who is coordinating all the vaccine trials in the U.S.
In the studies themselves, both of which were published in the New England Journal of Medicine, the method portion states that people received the Pfizer vaccine doses 21 days apart, and the Moderna doses 28 days apart. If the doses had different amounts of liquid vaccine or a different substance inside, the study would state the difference.
“The first dose and the second post are identical,” explained Corey. “[You can not mix] Pfizer and Moderna, but what's in that syringe is identical. The Pfizer first dose is the same as the Pfizer second dose, and [so is] the Moderna vaccine.”
So, we can verify there is no difference between the first and second doses of the vaccine. People’s reactions to the vaccines might differ, but it’s not because the first and second doses of the vaccine are different.