Kamil Krzaczynski | Reuters
Researchers leading the Com-COV study – which examines the feasibility of using a different vaccine for initial ‘primary’ vaccination to follow-up ‘booster’ vaccination – found that alternating doses of the two vaccines generated strong immunity.
However, the study found that immune responses differed depending on the order of vaccination, with the Oxford-AstraZeneca vaccine followed by the Pfizer-BioNTech vaccine generating the best immune response of the two mixed schedules.
Doses of the vaccines were given four weeks apart with data for a 12-week dose interval to come, the researchers said after posting their latest findings on the Lancet preprint server on Monday.
“The two” mixed “programs (Pfizer-BioNTech followed by Oxford-AstraZeneca and Oxford-AstraZeneca followed by Pfizer-BioNTech) induced high concentrations of antibodies against the peak IgG protein of SARS-CoV2 when the doses were lowered. administered four weeks apart, ”the researchers noted.
“This means that all possible vaccination schedules involving the Oxford-AstraZeneca and Pfizer-BioNTech vaccines could potentially be used against Covid-19. “
The findings could add much-needed flexibility to vaccination programs around the world, according to Matthew Snape, associate professor of pediatrics and vaccinology at the University of Oxford and lead investigator of the trial.
“The results show that when given four weeks apart, the two mixed regimens induce an immune response above the threshold set by the standard Oxford / AstraZeneca vaccine regimen. “
The researchers noted that the two mixed regimens induced higher antibodies than the “standard” two-dose Oxford-AstraZeneca regimen. Currently, it is recommended that the two doses required by the AstraZeneca vaccine be administered eight to 12 weeks apart. Previous clinical trials have found that the longer gap between doses increased the effectiveness of the AstraZeneca-Oxford vaccine, to 82.4%, against symptomatic Covid-19 infection.
The highest antibody response in the new study was seen after the two-dose Pfizer-BioNTech schedule, and the highest T-cell response was from an Oxford-AstraZeneca shot followed by Pfizer-BioNTech, have noted the researchers, without giving further details.
The Covid vaccines currently licensed in the UK and US stimulate our immune system to generate antibodies to protect us from infection. Antibodies are produced by specialized white blood cells called B lymphocytes or B cells. T lymphocytes, on the other hand, are a second type of white blood cell that also plays an important role in our immune system; T cells can both attack cells that have been infected with a pathogen or virus, such as Covid, and also help B cells make antibodies.
“These results are an invaluable guide to the use of mixed dose schedules, but the four week interval 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 results for a 12 week interval will be available shortly, ”added Snape.
The UK vaccination program has been applauded for its speed and agility so far. The UK was quick to clear and roll out the vaccines and are now offering everyone over 18 their first vaccines while giving the rest of the population their second dose. To date, 84.1% of all UK adults have received a first dose and 61.6% have received two doses of a Covid vaccine, according to government data.
“Our single-person (counterpart) vaccination program has already saved tens of thousands of lives across the UK, but we now know that mixing doses could give us even more flexibility for a booster program, while supporting countries that need to go further with their vaccines and that might encounter supply difficulties, ”he said.
In May, researchers reported preliminary data from Com-COV showing mild to moderate reactions more common in mixed programs compared to standard programs, however, these were short-lived.
Read more: Mix and Match vaccine study reveals increased risk of mild to moderate symptoms
The University of Oxford is leading the Com-COV study, led by the National Immunization Schedule Evaluation Consortium, and is supported by £ 7million ($ 9.7million) in government funding from the Vaccines Taskforce.