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Mixing vaccines provides good protection from COVID-19, study finds

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Alternating doses of the Oxford/AstraZeneca and Pfizer vaccines generate robust immune responses against COVID-19, an NIHR supported study has found.

Both options generate high concentrations of antibodies against the SARS-CoV2 spike IgG protein when doses were administered four weeks apart.

This means all possible vaccination schedules involving the Oxford/AstraZeneca and Pfizer vaccines could potentially be used against COVID-19.

The Com-COV study is led by the University of Oxford and recruited 830 volunteers aged 50 and above from eight sites, including 100 at Oxford Vaccine Group.

Professor Matthew Snape, Associate Professor in Paediatrics and Vaccinology at the University of Oxford, and Chief Investigator on the trial, said: “The results show that when given at a four-week interval both mixed schedules induce an immune response that is even better than that seen after the standard schedule of the Oxford/AstraZeneca vaccine. The investigators would like to thank the participants that made this important study possible.

“These results are an invaluable guide to the use of mixed dose schedules, however the interval of four weeks studied here is shorter than the eight to 12-week schedule most commonly used for the Oxford/AstraZeneca vaccine. This longer interval is known to result in a better immune response, and the results for a 12-week interval will be available shortly.” 

An Oxford/AstraZeneca then Pfizer/BioNTech schedule induced higher antibodies and T-cell responses than Pfizer/BioNTech then Oxford/AstraZeneca.

The highest antibody response was seen after the two-dose Pfizer schedule and the highest T-cell response from Oxford/AstraZeneca followed by Pfizer.

To volunteer to be contacted about taking part in trials, sign-up to the NHS COVID-19 Vaccine Research Registry.

Read more on the NIHR website.