Pfizer-AstraZeneca COVID-19 vaccine combination better than 2 AstraZeneca shots: Study

Washington: A study led by the Oxford University has discovered that alternating doses of the AstraZeneca and Pfizer-BioNTech vaccines generate robust immune responses against the coronavirus disease (Covid-19). The researchers, who are looking into the feasibility of using a different vaccine for the initial “prime” vaccination to the follow-up “booster” vaccination, discovered that alternating doses of the two vaccines generated strong immunity.

The study, published on the Lancet pre-print server, says "mixed" doses of these vaccines induced high concentrations of antibodies against the SARS-CoV2 spike IgG protein when they were given four weeks apart. The study indicated that all possible vaccination schedules involving the Oxford-AstraZeneca and Pfizer-BioNTech vaccines could potentially be used against coronavirus disease (Covid-19).

"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," Matthew Snape, an associate professor in paediatrics and vaccinology at the University of Oxford and the chief investigator, said.

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," he noted.

However, the study found that the immune responses differed according to the order of immunisation, with the Oxford-AstraZeneca shot followed by the Pfizer-BioNTech vaccine generating the better immune response out of the two mixed schedules.

Snape said that these results are an invaluable guide to the use of mixed dose schedules, but the interval of four weeks studied is shorter than the eight to 12-week schedule most commonly used for the Oxford-AstraZeneca vaccine.

The United Kingdom's vaccination program has been applauded for its speed and agility so far. It was quick to authorise and deploy vaccines and is now offering all over-18s their first shots while giving the remainder of people their second doses. To date, 84.1% of all UK adults have had the first dose and 61.6% have had two doses of a Covid-19 vaccine, government data shows.