London, Dec 7 (BUS): A major British study of mixing COVID-19 vaccines found that people had a better immune response when they received a first dose of AstraZeneca or Pfizer-BioNTech shots followed by Moderna nine weeks later, according to results on Monday.
“We found a really good immune response across the board … in fact, above the threshold set by two doses of the Oxford and AstraZeneca vaccines,” Matthew Snape, the Oxford professor in charge of the trial, called Com-COV2, told Reuters.
Findings that support flexible dosing will provide some hope for poor and middle-income countries that may need to combine different brands between the first and second shots if supplies decline or become unstable.
“I think the data from this study will be particularly interesting and valuable for low- and middle-income countries where they are still rolling out their first two doses of vaccines,” Snape said.
“We are showing… that you don’t have to commit too tightly to receiving the same vaccine for a second dose… and that if the program is delivered more quickly with multiple vaccines, it is okay to do so.”
If the AstraZeneca-Oxford (AZN.L) vaccine was followed by either Moderna (MRNA.O) or Novavax (NVAX.O), higher antibody and T-cell responses were induced against two doses of AstraZeneca-Oxford, according to researchers at the University of Oxford.
The study in 1,070 volunteers also found that a dose of Pfizer-BioNTech (PFE.N) (22UAy.DE) followed by a dose of Moderna (MRNA.O) was better than two doses of a standard Pfizer-BioNTech course.
Pfizer-BioNTech followed by Novavax induced higher antibodies than the two-dose Oxford-AstraZeneca schedule, although this schedule caused lower antibody and T-cell responses compared to the two-dose schedule of Pfizer-BioNTech.
No safety concerns have been raised, according to an Oxford University study and published in the Lancet medical journal.
Several countries were posting well-matched mix and match before strong data became available as countries faced rising infection numbers, low supplies and slow immunization due to some safety concerns.
The longevity of protection offered by vaccines is under scrutiny, with booster doses also being considered amid increasing cases. New variants, including Delta and Omicron, have increased pressure to speed up vaccination campaigns.
Researchers in the Com-COV2 study said blood samples from participants were tested against Wild-Type, Beta and Delta variants, adding that the efficacy of vaccines against variants had diminished, but this was consistent across mixed cycles.
Deploying vaccines using technology from different platforms — such as Pfizer and Moderna mRNA, the AstraZeneca viral vector and protein-based Novavax — and on the same timeline is new.
He said the findings may point to new approaches to immunization against other diseases.
The study also found that a first dose of the AstraZeneca-Oxford vaccine followed by any of the other candidates in the study generated a particularly strong response, consistent with findings in June.
The study is designed as a so-called “non-inferiority” study – the intent is to demonstrate that admixture is not significantly worse than standard schedules – and compares immune system responses with the gold-standard responses reported in previous clinical trials of each vaccine.
FKN