What you need to know about COVID-19 booster shots amid questions over mixing vaccines

People in high risk age groups can start getting a Pfizer COVID-19 booster shot, after officials with the Food and Drug Administration gave the go-ahead for the booster shots last week, but doctors are looking into whether or not mixing COVID-19 shots could help.

Currently, only Pfizer/BioNTech's COVID-19 booster shots have received emergency use authorization, but other brands might not be far behind, and at least some smaller studies show there can be benefits of mixing vaccines.

Chandler Doctor Andrew Carroll says patients have already been asking him about it.

"I think it is a good idea to get a boost, because it will help maintain this protection that you've enjoyed here for the last seven or eight or nine months, however long ago you got it," said Dr. Carroll.

Valleywise Health emergency care doctor Frank Lovecchio says he has seen early studies that show mixing and matching vaccines can be beneficial.

"There's many studies out there. They're small, but there are many studies that show if you got two Moderna shots and a Pfizer, your antibody levels will be higher, which suggest protection will be higher," said Dr. Lovecchio.

Currently, mixing shots is not recommended by federal officials. As far as supply, state officials say the rollout of booster shots will be much different than the initial vaccine rollout, as they have enough for boosters and people who still want a first dose.

"We're at a different stage now than we were in January or February, when vaccine supply was limited. We now have ample supply of vaccines across the state," said Jessica Rigler with the Arizona Department of Health Services.

Dr. Lovecchio says the bottom line is people should talk to their provider about the potential risks, and if they didn't get a Pfizer vaccine originally, they can wait. Some studies show Moderna has higher protection for longer, and their booster could be approved this fall or winter.

Who should get the booster?

Currently, people who got two Pfizer shots at least six months ago and who fall into one of these groups should get the booster:

  • People 65 and older, nursing home residents and assisted living residents.
  • Others ages 50 to 64 with a long list of risky health problems including cancer, diabetes, asthma, HIV infection and heart disease. Being overweight or obese is a category that qualifies roughly 70% of people in this age group.

The Centers for Disease Control and Prevention says these people may get a booster, but stopped short of a full recommendation:

  • People 18 to 49 who got their Pfizer shots at least six months ago with risky health problems can consider the booster based on their individual benefits and risks.
  • Anyone 18 to 64 with a risky job, such as health care, can consider boosters. Prisoners and people living in homeless shelters are also in this group.

Related: COVID-19 vaccine booster: Who is eligible for 3rd Pfizer shot?

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COVID-19 resources

CDC Website for COVID-19


https://espanol.cdc.gov/coronavirus/2019-ncov/index.html (In Spanish/En Español)

AZDHS Website for COVID-19


https://www.azdhs.gov/covid19/es/index.php (In Spanish/En Español)

AZDHS Website for COVID-19 Vaccination


https://www.azdhs.gov/covid19/es/vaccines/index.php (In Spanish/En Español)