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

Doctors and public health officials have been exploring various ways to maximize vaccine supplies - for example, by delaying the time between the first and second doses - as many low- and middle-income nations try to figure out how to cope with the vaccine shortage. The ability to mix doses could help countries with supplies of different vaccines help each other.

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

Flexible programs

Both vaccine combination programs produced more antibodies than two doses of Astra, the study revealed. The best T-cell response occurred with the Astra vaccine followed by the Pfizer vaccine, and the highest antibody response was seen with two doses of Pfizer.

"This advocates for flexibility in the use of these programs, when local circumstances require it," Matthew Snape, an Oxford professor who led the trial, told a news conference. "This gives everyone options."

AstraZeneca vaccine doses are currently administered 12 weeks apart in the UK, which extends accessibility and appears to increase the efficacy of the vaccine. Additionally, an Oxford study published Monday showed that giving the vaccines up to 10 months apart further improved responses. The results of a trial of the combined doses at 12-week intervals will be available "within the next month or so," Snape said at the briefing.

The trial involved 830 volunteers aged 50 and over and tested the vaccines only against the variant first identified in Wuhan. New tests against additional variants of the coronavirus could be useful in informing which vaccines and combinations to use in potential winter booster doses, Snape said. Additional program research will look at the combination of Moderna Inc. and Novavax Inc. vaccines.

Last month, preliminary research in the study revealed that the combination of Pfizer and Astra doses increased side effects, such as fatigue and headaches. However, the Lancet study findings indicated that these were short-lived.

Note:

The information in this article is not intended to influence your decision whether to be vaccinated. You should conduct your own research when making a decision.