British Study Says Mixing Pfizer Or AstraZeneca's COVID-19 Vaccine With Moderna Gives Better Immunity

Illustration of the COVID-19 vaccine alerted by Pfizer, Moderna and AstraZeneca. (Collage/VOI)

JAKARTA - A large UK study of blending COVID-19 vaccines has found that people have a better immune response when they receive the first dose of a shot of AstraZeneca or Pfizer's COVID-19 vaccine followed by Moderna nine weeks later, results showed Monday.

"We found an excellent immune response across the trials, in fact, higher than the threshold set by the two-dose Oxford-AstraZeneca vaccine," Matthew Snape, the Oxford professor behind the trial dubbed Com-COV2, told Reuters, as quoted December 7.

The findings in favor of flexible dosing will provide hope for poor and middle-income countries, which may need to combine different brands of first and second vaccines if supplies run low or become unstable.

"I think the data from this study will be very interesting and valuable for low- and middle-income countries, where they are still rolling out the first two doses of the vaccine," said Snape.

"We showed you don't have to be rigid about receiving the same vaccine for a second dose and if the program is going to be delivered more quickly using multiple vaccines then it's OK to do it," he said.

When the AstraZeneca-Oxford vaccine is followed by injections of Moderna or Novavax, higher antibody, and T-cell responses are induced than two doses of AstraZeneca-Oxford, according to researchers at the University of Oxford.

Illustration of a COVID-19 vaccination. (Wikimedia Commons/MDGovpics)

Meanwhile, a study of 1.070 volunteers also found that administering a dose of Pfizer-BioNTech vaccine followed by an injection of Moderna was better than the two standard doses of Pfizer-BioNTech.

And, administration of the Pfizer-BioNTech vaccine followed by Novavax induced higher antibodies than the two-dose Oxford-AstraZeneca vaccine, although this schedule induced lower antibody and T-cell responses than the two-dose Pfizer-BioNTech schedule.

No safety concerns were raised, according to the Oxford University study published in the medical journal 'Lancet'.

Many countries have implemented mix-and-match long before robust data are available, as countries are faced with soaring infection rates, low supplies, and slow immunization due to several safety concerns.

The longevity of protection offered by the vaccine has come under scrutiny, with booster doses being considered also amid soaring cases. New variants, including Delta and Omicron, have now increased pressure to accelerate vaccination campaigns.

Blood samples from participants were tested against the Wild-Type, Beta, and Delta variants, the Com-COV2 study researcher said adding, the vaccine's efficacy against the variants had diminished, but this was consistent across mixed courses.

To note, deploying vaccines using technologies from different platforms, such as Pfizer and Moderna mRNA, AstraZeneca virus vector and Novavax protein-based injections in the same schedule is nothing new.

The results could inform new approaches to immunization against other diseases, he said.

The study also found that the first dose of the AstraZeneca-Oxford vaccine followed by one of the other candidates in the study produced a very strong response, consistent with findings in June.

Later, the study was designed as a so-called "non-inferiority" study. The aim was to demonstrate that admixture was not substantially worse than the standard schedule and to compare the immune system response to the gold standard response reported in previous clinical trials of each vaccine.