Study shows mixing AstraZeneca and Pfizer vaccines generates strong immune response against COVID-19

Mixing doses of the Pfizer and AstraZeneca vaccines can generate a strong immune response against COVID-19, an Oxford University study has found. The study, conducted by Oxford Vaccine Group's Com-Cov vaccine trial, found that those who are given a dose of AstraZeneca followed by a dose of Pfizer four weeks later generated a better immune response.

Oxford developed the AstraZeneca vaccine, which is used in the U.K. In the U.S., three other COVID-19 vaccines are available: Moderna, Johnson & Johnson and Pfizer-BioNTech. The Oxford study recruited 830 volunteers, 50 years or older, in the U.K. to test four different vaccine combinations.