Here’s What Happens If You End Up Getting Two Different Vaccines

Since the COVID-19 vaccine has steadily become more available to people across the United States, roughly 29% of the population has received at least one dose. And although only 16% of the country is fully vaccinated, President Joe Biden announced that all adults will be eligible for the shot by May 1. Until then, many qualifying groups across the country remain the same: people over the age of 55, healthcare and essential workers, people aged 16 and older, and those with underlying medical conditions being some of the few.

But with appointments missed and many hunting for leftovers, one question is starting to cross our minds: what happens if you somehow get two different vaccine doses?

According to the Centers for Disease Control and Prevention (CDC), while more research is needed on the subject, there should be no side effects to mixing vaccines. The Cleveland Clinic turned to the CDC's findings in their own research on mixing different types of COVID-19 vaccine shots in February; according to the CDC, medical professionals administering vaccinations should do their best to ensure patients receive two of the same shots if they're administering the Pfizer-BioNTech or Moderna vaccine.

However, in an "exceptional situation" where a second shot of the first vaccine type isn't available, "any available mRNA COVID-19 vaccine may be administered at a minimum interval of 28 days between doses to complete the mRNA COVID-19 vaccination series.”

With COVID-19 vaccines becoming more accessible to people around the world, scientists in the United Kingdom are almost two months into testing whether it's safe to mix vaccination types. These trials, currently being held at Oxford University in London, began after the country gave their medical professionals the okay to mix vaccine shots in January. Volunteers in the trial will either receive one dose of the Pfizer vaccine followed by one dose of the AstraZeneca vaccine, the reverse, or two regular doses of each vaccine type. Eight hundred and thirty-three volunteers over the age of 50 are being tested, and the gaps between the groups range from four to 12 weeks to get a clearer picture of how everyone is affected.

Scientists and medical professionals began testing the blood of volunteers in the U.K. trial in March, and it is expected to continue through April.