Mixing AstraZeneca and Pfizer Covid jabs 'generates robust immune response'

28 June 2021, 16:13 | Updated: 28 June 2021, 16:27

Mixing the Pfizer-BioNTech and Oxford-AstraZeneca vaccines generates a robust immune response against coronavirus, research has found.

The Com-COV study, run by the University of Oxford, found that using the Pfizer and AstraZeneca vaccines interchangeably resulted in high concentrations of antibodies against the virus, when given four weeks apart.

Findings also suggested that the order of vaccines made a difference, with the AstraZeneca followed by Pfizer inducing higher antibodies than if the Pfizer were given first.

That said, both schedules produced higher antibodies than the standard two-dose AstraZeneca schedule.

Professor Matthew Snape, chief investigator on the trial and associate professor in paediatrics and vaccinology at the University of Oxford, said: "The Com-COV study has evaluated 'mix and match' combinations of the Oxford and Pfizer vaccines to see to what extent these vaccines can be used interchangeably, potentially allowing flexibility in the UK and global vaccine rollout.

"The results show that when given at a four-week interval both mixed schedules induce an immune response that is above the threshold set by the standard schedule of the Oxford-AstraZeneca vaccine.

"The investigators would like to thank the participants that made this important study possible."

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More flexibility with vaccines could help in the rollout on a global scale, with people being able to receive any jab that is available instead of having to wait for a matching one.

However, the findings were from an interval of four weeks between each dose, which is much shorter than the eight to 12-week schedule that is currently being used.

Professor Snape said: "This longer interval is known to result in a better immune response, and the results for a 12-week interval will be available shortly."

Deputy chief medical officer, Professor Jonathan Van-Tam, explained that results from the study of the 12-week interval could make a bigger difference in decisions around the vaccine rollout.

"Today's data are a vital step forward, showing a mixed schedule gives people protective immunity against Covid-19 after four weeks," he said.

"Equally, they offer supportive evidence that the standard (non-mixed) JCVI (Joint Committee on Vaccination and Immunisation) recommendations for Covid-19 vaccination all produce highly satisfactory immune responses, for both main vaccines in use.

"Given the UK's stable supply position there is no reason to change vaccine schedules at this moment in time.

"The results for the 12-week interval, which are yet to come, will have an instrumental role to play in decisions on the future of the UK's vaccination programme.

"Our non-mixed vaccination programme has already saved tens of thousands of lives across the UK but we now know mixing doses could provide us with even greater flexibility for a booster programme, while also supporting countries who have further to go with their vaccine rollouts and who may be experiencing supply difficulties."