Mixing Astra and Pfizer Shots Creates Strong Immune Response

Mixing doses of Covid-19 vaccines from Pfizer Inc. and AstraZeneca Plc creates a strong immune response, according to results from a University of Oxford study, a finding that could enable greater flexibility in the use of scarce supplies.

A mixed schedule of the Pfizer shot followed by the Astra vaccine, and vice versa, resulted in high concentrations of antibodies against Covid-19 when given four weeks apart, researchers reported Monday in the Lancet medical journal.

Injection with AstraZeneca vaccine in Taiwan

Photographer: I-Hwa Cheng/Bloomberg

Doctors and public health officials have been analyzing various ways to extend vaccine supplies -- by delaying the time between first and second doses, for ...