We would like to thank all our Com-COV and Com-COV2 study volunteers for their participation in these trials. Data from these studies have affected vaccine policy in the UK, and around the world.
Links to all publications arising from these trials can be found on the NISEC website. We will update this page whenever we have new information relating to our participants.
In the Com-COV study we have so far found that immunisation with the two ‘mixed’ schedules (Oxford/AstraZeneca followed by Pfizer or Pfizer followed by Oxford/AstraZeneca) produces antibody and T cell responses higher than that seen after two doses of the Oxford/AstraZeneca, which is known to be highly effective against severe disease. Short-term side effects are higher after the second dose in people who receive a “mixed” schedule, but there have been no safety concerns raised in the study.
In the Com-COV2 study we found that all the studied mixed-schedules (Oxford/AstraZeneca followed by Novavax or Moderna and Pfizer followed by Novavax or Moderna) were able to produce a response from both antibodies and T-cells in the immune system. All combinations produced antibodies that were higher than two doses of the Oxford/AstraZeneca vaccine. Short-term side effects after vaccination were higher in people who had Moderna as a second dose, but not in those who had Novavax.
The results from both these studies have been very reassuring, as have shown that mixed vaccine schedules are able to produce immune system responses that are above that of the Oxford/AstraZeneca vaccine – a vaccine that we know has very high real-world protection against severe disease and death.
These results are important because they show that countries can be more flexible in their approach to vaccination, potentially improving access to COVID-19 vaccines.
The most recent data from the Com-COV2 study relate to the Omicron variant of concern and are presented in a letter. These show that immune system antibody responses (neutralising antibodies) against the Omicron variant are lower in people who have had two doses of Oxford/AstraZeneca than two doses of Pfizer COVID-19 vaccine. The results presented in this letter are only from participants who had two doses of Oxford/AstraZeneca or Pfizer vaccines and are based on samples taken at one month after the second vaccine. We do not yet have information on the immune response of participants response of participants who received “mixed” vaccines against the Omicron SARS-CoV-2 variant.
We know from work published by the UK Health Security Agency that having a third dose is important to improve protection against the SARS-CoV-2 omicron variant and we would strongly encourage all our participants who have not yet received a third-dose booster to consider doing so.
If you do decide to do this, we would like to invite you for an end of study visit beforehand, so please contact your study site to discuss.
General information for COVID-19 vaccine trial participants from the National Institute of Health Research can be found here:
The Oxford Vaccine Group