Mixing medications is usually a huge no-no, but a surprising new study has shown that it may be an effective strategy when it comes to Covid-19 vaccines. A study out of Oxford University, in England, has shown that people who were given a dose of AstraZeneca’s vaccine followed by Pfizer’s generated a better immune response than those who received two doses of the same vaccine. The study, published in The Lancet medical journal in late June, was undertaken by Oxford Vaccine Group’s Com-Cov vaccine trial. It involved testing four different vaccine combinations (including standard “homologous” combinations, or two doses of the same vaccine) on 830 volunteers from the U.K., all of whom were at least 50 years old. Of all the tested combos, a mix of Pfizer and AstraZeneca yielded the highest antibodies and T-cell responses, especially when AstraZeneca was administered first. Why the order of the shots mattered is still a mystery.

What’s not so mysterious is the impact of this new information. Not only is it valuable to know which vaccines work best together, knowing that certain vaccines can be safely mixed could allow suppliers to mix and match what they have available, helping doses reach the highest number of people possible. In an interview with CBS News, Deputy Chief Medical Officer Professor Jonathan Van-Tram explained, “Our non-mixed (homologous) vaccination program has already saved tens of thousands of lives across the U.K., but we now know mixing doses could provide us with even greater flexibility for a booster program, while also supporting countries who have further to go with their vaccine rollouts and who may be experiencing supply difficulties.” Oxford’s investigations into Covid-19 vaccine mixtures isn’t over. In fact, six new “arms” of the mixing-trial are now in the process of recruiting around 175 candidates each. Among other combinations, a regimen of Moderna and Novavax will soon be tested. According to a press release, the study’s overall intent is to “demonstrate that mixing is not substantially worse than not mixing.” Here’s hoping that these new findings will help get more shots into more arms!

[Image description: Empty bottles of various Covid-19 vaccines.] Credit & copyright: Christof Stache/AFP/Getty

Written by: Maria C.
More about this Curio:
BBC: "Mixing Covid Jabs Has Good Immune Response, Study Finds."
CBS News: "Study Shows Mixing AstraZeneca and Pfizer Vaccines Generates Strong Immune Response Against COVID-19."
Wall Street Journal: "Vaccine Mix Study Suggests Combinations Safe and Effective."