AZ and Pfizer can be safely mixed to boost immunity: Study

LONDON: Doses of the Astrazeneca and Pfizer vaccines can be “mixed and matched” to generate a strong immune response against COVID-19, new research shows.

The Com-cov study, led by Professor Mathew Snape of Oxford University, has demonstrated that people can safely receive a first shot of the Astrazeneca vaccine followed by a second dose of the Pfizer jab over a four-week period – and vice versa.

Known as a heterologous prime-boost, this type of vaccination induces “high concentrations” of antibodies that target the spike protein which covers the outside of Sars-cov-2, the study found.

The data provides support for the decision of some European countries that have started offering alternatives to Astrazeneca as a second shot ater the vaccine was linked to rare blood clots.

Mathew Snape, the Oxford professor behind the trial, said that the findings could be used to give flexibility to vaccine rollouts, but was not large enough to recommend a broader shit away from clinically approved schedules on its own.

“It’s certainly encouraging that these antibody and T-cell responses look good with the mixed schedules,” he told reporters. “But I think your default has to stay, unless there’s a very good reason otherwise, to what is proven to work,” he added referring to the same-shot vaccine schedules assessed in clinical trials.

The highest antibody response was seen in people receiving two doses of Pfizer vaccine, with both mixed schedules producing beter responses than two doses of Astrazeneca vaccine.

An Astrazeneca shot followed by Pfizer produced the best T-cell responses, and also a higher antibody response than Pfizer followed by Astrazeneca.

The results were for combinations of vaccines given at four week intervals to 830 participants.

COM-COV is also looking at mixed schedules over a 12-week interval, and Snape noted that Astrazeneca’s shot was known to produce a beter immune response with a longer interval between doses.