Study suggests AstraZeneca followed by Pfizer, 4 weeks apart, gives strong immunity

According to the results of a study recently conducted by a University of Oxford, mixing doses of Covid-19 vaccines from Pfizer Inc. and AstraZeneca Plc creates a strong immune response against Covid-19.

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.

The order in which people got the vaccines affected the results. Astra followed by Pfizer produced higher levels of immune antibodies and T-cells than Pfizer followed by Astra.

Doctors and public health officials have been analyzing various ways to extend vaccine supplies — by delaying the time between first and second doses, for example — as many low- and middle-income nations try to figure out how to cope with vaccine scarcity. The ability to mix doses might help countries with supplies of different vaccines assist one another.