Mixing AstraZeneca and Pfizer vaccines generates strong immune response against COVID-19
Coronavirus spike is 'in unvaccinated groups' says expert
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Alternating doses of the Oxford-AstraZeneca and Pfizer-BioNTech vaccines generates a robust immune responses against COVID-19, according to researchers running the University of Oxford-led Com-COV study. In a paper published on the Lancet pre-print server, they report that both “mixed” schedules (Pfizer-BioNTech followed by Oxford-AstraZeneca, and Oxford-AstraZeneca followed by Pfizer-BioNTech) induced high concentrations of antibodies against the SARS-CoV2 spike IgG protein when doses were administered four weeks apart. The finding suggests there could be greater flexibility and overlap in vaccination schedules involving the Oxford-AstraZeneca and Pfizer-BioNTech vaccines moving forward.
Professor Matthew Snape, Associate Professor in Paediatrics and Vaccinology at the University of Oxford, and Chief Investigator on the trial, 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 roll-out.
“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.”
A significant finding related to the order the vaccines administered.
Receiving the Oxford-AstraZeneca vaccine first and the Pfizer-BioNTech second induced higher antibodies and T-cell responses than Pfizer-BioNTech/Oxford-AstraZeneca, and both of these induced higher antibodies than the licensed, and highly effective “standard” two-dose Oxford-AstraZeneca schedule.
The highest antibody response was seen after the two-dose Pfizer-BioNTech schedule, and the highest T cell response was observed from Oxford-AstraZeneca followed by Pfizer jab.
The T cell response is an integral and essential part of the host immune response to to virus infection.
Professor Matthew Snape said: “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”.
Deputy Chief Medical Officer Professor Jonathan Van-Tam said: “Today’s data are a vital step forward, showing a mixed schedule gives people protective immunity against COVID-19 after four weeks.
“Equally, they offer supportive evidence that the standard (non-mixed) JCVI 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 (homologous) 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.”
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