According to researchers managing a University of Oxford-led Com-COV study, alternating doses of the Oxford-AstraZeneca and Pfizer-BioNTech vaccines generated robust immune responses against Covid-19.
If trials from the United Kingdom continue to show a similar response, combinations of vaccines could add resources and flexibility to the worldwide Covid-19 vaccination effort.
The AstraZeneca-Oxford vaccine has not been approved in the U.S. The Biden Administration had been expected to distribute some of the US supply of AZ vaccine to other nations. However, the process has been held up by problems at a Baltimore-area plant that was producing the vaccine.
AZ has headquarters, manufacturing, and logistics operations in northern Delaware.
Professor Matthew Snape, associate professor in Pediatrics and Vaccinology at the University of Oxford and chief investigator on 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,” Snape says.
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.”