The Spanish health authorities made the decision to recommend Pfizer in those vaccinated with the first dose of AstraZeneca under 60 years of age after knowing the results of the Spanish study. A finding that coincides with the preliminary conclusions of the Com-Cov study carried out by the University of Oxford.
An article published on the Lancet journal preprint server reveals that both mixed programs (Pfizer-BioNTech followed by Oxford-AstraZeneca and Oxford-AstraZeneca followed by Pfizer-BioNTech) induced high concentrations of antibodies against the Covid-19 virus when doses were given four weeks apart.
“The results show that when given four weeks apart, both combination schedules induce an immune response that is above the threshold set by the standard Oxford/AstraZeneca vaccine schedule,” said Matthew Snape, Associate Professor of Pediatrics and vaccination at the University of Oxford and chief investigator of the trial.
Thus, the main conclusion of the study is that “all possible vaccination schedules involving the Oxford-AstraZeneca and Pfizer-BioNTech vaccines could potentially be used against Covid-19,” says the statement distributed by the university. However, the order of the factors does affect the result: with Oxford-AstraZeneca followed by Pfizer-BioNTech, a better immune response is generated.
“These results are an invaluable guide to the use of mixed-dose schedules; however, the four-week interval studied here is shorter than the more commonly used eight- to 12-week schedule for the Oxford-AstraZeneca vaccine. It is known that this longer interval results in a better immune response, and results for a 12-week interval will be available shortly,” adds Matthew Snape.
Another of the findings of this work was announced in May. The researchers reported that the combination of vaccines revealed more frequent mild-to-moderate reactions in mixed schedules compared to standard schedules; however, these were short-lived.
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