Second dose of treatment generates response among young people during Oxford University trial.
Researchers leading the University of Oxford’s Com-COV3 study have delivered results from a study researching the immune response and side-effect profile of ‘mixed’ two-dose COVID-19 vaccine schedules.
The trial unfolded in adolescents aged between 12 and 16 years who received either a full or a one-third dose of the Pfizer-BioNTech COVID-19 vaccine – or a full dose of the Novavax vaccine at least eight weeks after a first full dose of the Pfizer-BioNTech vaccine.
Researchers shared that a mixed schedule using a full dose of Pfizer-BioNTech followed by a full dose of Novavax generated higher antibody and T cell responses and triggered fewer break-through infections compared to the licensed full dose Pfizer-BioNTech schedule. Furthermore, the mixed schedule combated both wild-type COVID-19 and Omicron COVID-19 variants.
While all mixed and non-mixed vaccine schedules used in the study demonstrated favourable side effect profiles, participants who received fractional dose Pfizer-BioNTech as their second vaccine also reported fewer and milder side effects compared to the other study groups. Critically, no safety concerns were raised in the 148 participants in the 12 to 16 years age group.
This research becomes the first to report results from a randomised, controlled study analysing the immune response and side-effect profiles of standard and mixed COVID-19 vaccines among adolescents.
Dr Angela Minassian, chief investigator on the trial at the Oxford Vaccine Group, elaborated: “This study has embodied an incredible effort from our collaborating UK sites and the willing young people who took part. Together we have shown that mixed and fractional doses of COVID-19 vaccine schedules studied are well-tolerated and generate robust immune responses in adolescents for at least eight months.”
She added: “Of particular interest is the enhanced performance of Novavax’s protein subunit vaccine following a dose of Pfizer-BioNTech’s mRNA, compared to the standard two doses of Pfizer-BioNTech mRNA.”
“Amongst participants who had not been infected with COVID-19 before, those in the Novavax group were less likely to report a breakthrough infection than those in the standard Pfizer-BioNTech group. While interpretation should be cautious considering the study’s small sample size, this suggests that a combination of vaccine platforms may result in a greater breadth of protection,” she concluded.