Mix and matching COVID-19 jabs gives high immunity, finds Oxford's study

Matching COVID-19 vaccines give people a better immune response when they receive the first dose of AstraZeneca or Pfizer-BioNTech shots followed by Moderna nine weeks later, according to the Oxford University study published in the Lancet medical journal.

“We found a really good immune response across the board … in fact, higher than the threshold set by Oxford-AstraZeneca vaccine two doses,” Matthew Snape, the Oxford professor behind the Com-COV2 trial, told the Reuters news agency on Monday.

If the AstraZeneca-Oxford vaccine is followed by a Moderna or Novavax shot, higher antibodies and T-cell responses were induced versus two doses of AstraZeneca-Oxford, according to researchers at the University of Oxford.

The findings supporting flexible dosing will offer some hope to low- and middle-income countries that may need to mix vaccines for first and second doses if supplies run low or become unstable.

“We’re showing … you don’t have to stick rigidly to receiving the same vaccine for a second dose … and that if the program will be delivered more quickly by using multiple vaccines, then it is OK to do so,” added Snape.

The study of 1,070 volunteers also found that a dose of the Pfizer-BioNTech vaccine followed by a Moderna shot was better than two doses of Pfizer-BioNTech.

Pfizer-BioNTech followed by Novavax induced higher antibodies than the two-dose Oxford-AstraZeneca schedule, 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 published study.

Many countries have been deploying a mix-and-match approach well before the new data was available, as they grappled with soaring infection numbers, low supplies, and slow immunization over some safety concerns.

The longevity of protection offered by vaccines has been under scrutiny, with booster doses being considered as well amid surging cases. The discovery of new variants, including Delta and Omicron, has increased the pressure to speed up vaccination campaigns.

Blood samples from participants were tested against the Wild-Type, Beta, and Delta variants, researchers of the Com-COV2 study said, adding that vaccines’ efficacy against the variants had waned, but this was consistent across mixed courses.

Deploying vaccines using different technology like Pfizer-BioNTech and Moderna’s mRNA, AstraZeneca’s viral vector, and Novavax’s protein-based shot within the same schedule is a relatively new approach.

The results may inform new approaches to immunization against other diseases, according to Oxford researchers.