Why You Need Two Shots of the Moderna & Pfizer Vaccines

02.02.2021 | 3 min read

This information is current as of Feb. 2, 2021. For more recent updates on COVID-19 vaccines, visit COVID-19 Vaccines: Get the Facts. Vaccines made by Pfizer-BioNTech and Moderna have received emergency use authorization from the U.S. Food and Drug Administration for use against the new coronavirus and require two doses to be fully effective. All COVID-19 vaccines currently available in the United States have been shown to be highly effective at preventing COVID-19. However, wearing masks in shared spaces, staying socially distant and frequently washing your hands are critical measures to continue as vaccines are distributed – even if you have been vaccinated yourself. The Michigan Department of Health and Human Services is managing how the vaccines are distributed and administered throughout the state. State officials continue to expand vaccine eligibility as more vaccines become available.

Find out how to get a COVID-19 vaccine by visiting Michigan.gov/COVIDvaccine.

Why a two-part vaccine?

It is a common practice for a vaccine to require a second dose. The two-part regimen of the Pfizer and Moderna COVID-19 vaccines are like shots adults receive to prevent shingles and the ones teens receive to prevent HPV. The first shot starts building protection. A second shot a few weeks later is needed to get the most protection the vaccine has to offer. The vaccine from Pfizer-BioNTech requires a second shot three weeks after the first one. Moderna’s vaccine requires a second dose a month later. While the first shot has been shown in clinical trials to provide protection, a second shot is needed to make sure the vaccine will provide long-lasting immunity. The second dose also should be from the same vaccine manufacturer as the first dose, so state health officials said it is best to stick with the same provider for both shots. Both the Pfizer-BioNTech and Moderna vaccines use a new type of vaccine with messenger RNA instead of using a live virus. The messenger RNA tells your body’s cells to make a specific protein, which then activates to produce an immune response should you encounter the coronavirus that causes COVID-19.

Second-dose reminders

Knowing it might be difficult for some people to remember when to get their second COVID-19 vaccination, state and federal health officials have mapped out multiple ways for people to be reminded when the last step of the two-part shot is due. Here are some of the reminders in the works:

COVID-19 vaccination reminder card will be given to people receiving the first dose of the vaccine. It has space for a written reminder for a second-dose appointment.
People with smartphones are being asked to take a picture of these reminder cards and add the due date for the second dose to their calendars.
MDHHS is developing text messaging reminders that will be sent prior to a person’s second dose.
The U.S. Centers for Disease Control and Prevention has a “V-safe After Vaccination Health Checker” app for smartphones. It can send people reminders when they are due for a second dose.