Professor Snape's study on mixing COVID-19 vaccines announces its results

matthew snape

The study on mixing different COVID-19 vaccines led by St Cross Member of Common Room Professor Matthew Snape, Associate Professor in Paediatrics and Vaccinology at the University of Oxford, has reported results supporting flexible second dose options following Oxford-AstraZeneca or Pfizer-BioNTech jabs.

According to the paper published in the Lancet, when given a first dose of the Oxford-AstraZeneca or the Pfizer vaccines followed nine weeks later by a second dose of COVID-19 vaccines manufactured by Novavax or Moderna it created a robust immune response.

No safety concerns were raised in this study of 1,070 participants, who took part in the study.

Chief investigator of the trial Professor Snape commented:

Thanks to studies such as these, we are now getting a more complete picture of how different COVID-19 vaccines can be used together in the same vaccine schedule. Encouragingly, all these schedules generated antibody concentrations above that of the licensed and effective two dose Oxford-AstraZeneca schedule. It’s only through the inspiring efforts of the Com-COV2 participants and study teams that we can generate these data; this will help get the world immunised against COVID-19 as quickly as possible.

The study confirmed that the primary vaccine made a difference to the immunogenicity of the various schedules as follows:

  • Oxford-AstraZeneca followed by Moderna/Novavax schedules both induced higher antibodies and T-cell responses than the licensed and highly effective ‘standard’ two-dose Oxford-AstraZeneca schedule.
  • Pfizer-BioNTech/Moderna induced higher antibody and T-cell responses than the standard two-dose Pfizer-BioNTech schedule
  • Pfizer-BioNTech/Novavax induced higher antibodies than the two-dose Oxford-AstraZeneca schedule; this schedule induced lower antibody and T-cell responses than two-dose Pfizer-BioNTech schedule.

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.

In addition, 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 either Oxford-AstraZeneca or Pfizer-BioNTech.

Professor Snape said:

Using different types of vaccines within the same schedule as we have done here (for example mRNA vaccines, viral-vector vaccines or protein-based vaccines) is a relatively novel approach to immunisation. As well as providing evidence for flexibility in deployment, these results suggest this approach can also help generate better immune responses. This has implications beyond COVID-19 and will inform new approaches to immunisation against other diseases that are, as yet, not vaccine preventable.

In September, the study was further expanded to explore multiple options for second dose COVID-19 vaccines in young people aged 12 to 16 years.