A new trial being run out of the University of Oxford will look at outcomes when individuals receive doses of two different COVID-19 vaccines. Over 800 participants aged 50 and up will receive the AstraZeneca vaccine followed by Pfizer’s vaccine or vice versa, or two doses of each. Doses will be given at 4- and 12-week intervals to also study the effect of spacing. While researchers hope to prove that there is no concern with mixing vaccines, a development that could greatly ease the logistics of widespread inoculation, some scientists are optimistic that mixing could be proven to offer an even greater immune response than using two doses of the same vaccine.