If You're Getting A Two-Shot Vaccine, Do The Shots Have To 'Match'?

by Colleen Dilthey Thomas
Scary Mommy and Yulia Reznikov/Getty

Vaccine is the buzzword of the minute. Everyone is talking about getting a vaccine, scheduling a vaccine or the people they know who have received a vaccine. Families are reuniting for the first time in more than a year because according to the CDC, 19% of the U.S. population is fully vaccinated against the COVID-19 virus, and 33% have had at least one dose. Vaccines are bringing people peace of mind after a year of fear and loss. People grapple with which vaccine is best? Which is the most effective? Which will give the least chance for side effects? But recently people have started talking about something new. What if you mixed vaccines? Like take a Pzifer first and follow up with Moderna in a few weeks? Is it safe? Or effective? Inquiring minds want to know!

In January, Britain made a suggestion that stunned healthcare experts. If you’ve had a dose of one vaccine and the second isn’t available, go ahead and mix things up. Caveat, if the original vaccine manufacturer is available, stick with it. But to vaccinate as much of Britain as quickly as possible, they say that mixing manufacturers seems to be OK. As reported in the New York Times, according to Britain’s new guidance, “every effort should be made” to complete a dosing regimen with the same shot first used. But when “the same vaccine is not available, or if the first product received is unknown, it is reasonable to offer one dose of the locally available product” the second time around.

At the time, this suggestion had no testing to back it up. The New York Times notes that clinical trials at the University of Oxford began in February when volunteers were given a dose of Pfizer-BioNTech vaccine then a dose of AstraZeneca’s, or vice versa. Soon those volunteers blood will be tested to see if mixing the vaccines was in fact effective. Without that analysis though, it’s like throwing darts and hoping one hits a bullseye.

At this time, there are other vaccines being developed in Britain, some in clinical trials while others are being tested in animals. As those vaccines are approved, they will begin to mix doses with the additional vaccines to create even more potential dosing combinations. Some researchers think that two different doses may in fact work better than just one. “I think we’re on the cusp of some interesting data,” said Adam Wheatley, an immunologist at the University of Melbourne in Australia in The New York Times report.

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The Times also stated that a heterologous prime-boost, the fancy term for mixing vaccines, has been used for years. Trials in mice have been done for vaccinations against influenza, Ebola and HIV. But due to cost and the amount of work, clinical trials have not been possible. With COVID-19, things are a bit easier. These drug manufacturers are making parallel products; therefore, they can be tested together. Hopefully with clinical trials moving forward daily, we’ll have a better idea of what truly is safe and effective soon.

In the United States, the CDC has noted that the authorized COVID-19 vaccines “are not interchangeable,” and that “the safety and efficacy of a mixed-product series have not been evaluated. Both doses of the series should be completed with the same product.” OK. So what is the real deal? Is it safe and effective or not? In theory, yes, but is it a good idea, maybe. The truth is, we really don’t know yet. Just as it took time for the vaccinations to be developed and approved, it will take time and trials to determine the effectiveness of a mix-and-match.

But until we know for sure, the CDC does have a few recommendations to help make sure that you receive your second dose of the same vaccine and have it administered on time.

  1. Hold on to your card. Vaccination sites should be providing a written record of your vaccination for you to take with you. Information such as your name, the date and the vaccination dosage that you have received will be on that card. Keep that!
  2. Register for v-safe. This is a smart-phone tool that allows you to provide feedback on your vaccine, how you are feeling and to set up reminders for the second dose.
  3. After you’ve enrolled in v-safe, sign up for VaxText, a free service that will send you a second dose reminder.
  4. Make sure that your immunization record is recorded in the Immunization Information System or ISS. Also get that vaccine info into your medical records.
  5. Finally, make your appointment for the second dose before leaving the vaccination site to help ensure that you will receive the same vaccine type the next go around.

So what can you do in the meantime? President Biden has announced that all adults will be eligible for a vaccine by April 19th. If you’re able, get that vaccine and a little peace of mind. But follow the protocols given by the organization distributing the vaccine. The faster adults are vaccinated, the closer we will be to getting back to our new normal.

Information about COVID-19 is rapidly changing, and Scary Mommy is committed to providing the most recent data in our coverage. With news being updated so frequently, some of the information in this story may have changed after publication. For this reason, we are encouraging readers to use online resources from local public health departments, the Centers for Disease Control, and the World Health Organization to remain as informed as possible.