A study backed by the UK government finds that mixing and matching Covid-19 vaccines may result in higher protection against the virus. People vaccinated with AstraZeneca for their first dose, and topped up with Pfizer, had nine times more antibodies than those who took two AstraZeneca doses. Researchers of the Oxford University said the findings strongly suggested the approach could enhance immunity, although, antibodies are just one part of the immune response.
Chief investigator of the study, Professor Matthew Snape said the UK should stick to its standard dosing regimen because it was proving to work in the real world. He warned there was a danger of complicating the hugely successful roll-out, which has seen four-fifths of the adult population getting at least one vaccine. Speaking in a press brief, he said, “The default has to stay to what is proven to work.”
Scientists of the study said the findings opened the door for more flexible roll-outs in countries with limited supplies. They will continue to monitor 830 participants in the trial to see how much protection the 'mix and match' strategy provides against Covid in the real world. Published in The Lancet, the study looked at the efficacy of either two doses of Pfizer, two of AstraZeneca, or one of them followed by the other.
The Com-Cov trial found that AstraZeneca's vaccine followed by Pfizer's induced higher levels of antibodies and T cells than vice versa. The mix-match approach produced more antibodies than two regular doses of AstraZeneca's, no matter which way round the jabs were given. All second doses were given four weeks apart and the trial recruited 830 volunteers who were aged 50 and above. All combinations worked well, priming the immune system.
The largest antibody levels were induced after two doses of Pfizer, and the highest T cell response was from AstraZeneca's followed by Pfizer. Prof Snape said the findings will give officials confidence that in case the Covid situation in the country changes, there are different dosing strategies that are safe and highly effective.
