Study supports flexible second dose options following Pfizer or Oxford jabs

First doses of the Oxford/AstraZeneca or Pfizer/BioNTech coronavirus vaccines with second doses of the Moderna or Novavax jabs will generate robust immune responses against Covid-19, researchers have found.

According to the study, participants who received a first dose of the Oxford of Pfizer jab generated a robust immune response when given a second dose of vaccines manufactured by Novavax or Moderna nine weeks later.

No safety concerns were raised in this study of 1,070 participants, the University of Oxford-led Com-COV study found.

Researchers say the study supports the flexible use of these vaccines in primary immunisation schedules, which is crucial to help their rapid deployment especially in low-and middle-income countries where vaccine supply may be inconsistent.

“Encouragingly, all these schedules generated antibody concentrations above that of the licensed and effective two-dose Oxford/AstraZeneca schedule.

“When it comes to cellular immunity, having a first dose of the Oxford/AstraZeneca vaccine followed by any of the other study vaccines generates a particularly robust response.”

The research found that both Oxford followed by Moderna/Novavax schedules both induced higher antibodies and T-cell responses than the licensed and highly effective standard’ two-dose Oxford schedule.

Pfizer/Moderna induced higher antibody and T-cell responses than the standard two-dose Pfizer schedule.

And Pfizer/Novavax induced higher antibodies than the two-dose Oxford schedule which induced lower antibody and T-cell responses than the two Pfizer doses.

Researchers also looked at the vaccine responses to different coronavirus variants.

Blood samples taken from participants were tested for their effectiveness against the Wild-Type, Beta and Delta variants.

While it was observed that the vaccines’ efficacy against the variant strains had decreased, this was a consistent trend across the mixed schedules.

The study, published in The Lancet, also found that a significantly higher number of short-lived vaccine reactions were reported in volunteers who received a second dose of Moderna compared to those who received two doses of the Oxford or Pfizer jabs.