In an analysis, submitted as a pre-print prior to peer-review publication, a two-dose regimen of the ChAdOx1 nCoV-19 vaccine provides minimal protection against mild-moderate COVID-19 infection from the B.1.351 coronavirus variant first identified in South Africa.
Efficacy against severe COVID-19 infection from this variant was not assessed. The analyses being submitted in the pre-print show the vaccine had high efficacy against the original coronavirus strain in South Africa.
Researchers from the University of Witwatersrand and others in South Africa and the University of Oxford, UK found that viral neutralisation by sera induced by the ChAdOx1 nCoV-19 coronavirus vaccine against the B.1.351 coronavirus variant were substantially reduced when compared with the original strain of the coronavirus.
These early data, have been submitted for scientific peer-review, appear to confirm the theoretical observation that mutations in the virus seen in South Africa will allow ongoing transmission of the virus in vaccinated populations, as has been recently reported even in those with prior infection due to earlier circulating variants.
In this study of approximately 2,000 volunteers who were on average 31 years old, mild disease was defined as at least one symptom of COVID-19. Protection against moderate-severe disease, hospitalisation or death could not be assessed in this study as the target population were at such low risk.
Work is already underway at the University of Oxford and in conjunction with partners to produce a second generation of the vaccine which has been adapted to target variants of the coronavirus with mutations similar to B.1.351, if it should prove necessary to do so.
Shabir Madhi, Professor of Vaccinology and Director of the Vaccines & Infectious Diseases Analytics (VIDA) Research Unit at University of the Witwatersrand, and Chief Investigator on the trial in South Africa said: “Recent data from a study in South Africa sponsored by Janssen which assessed moderate to severe disease, rather than mild disease, using a similar viral vector, indicated that protection against these important disease endpoints was preserved.
“These findings recalibrate thinking about how to approach the pandemic virus and shift the focus from the goal of herd immunity against transmission to the protection of all at risk individuals in population against severe disease.”
Andrew Pollard, Professor of Paediatric Infection and Immunity, and Chief Investigator on the Oxford vaccine trial, said: “This study confirms that the pandemic coronavirus will find ways to continue to spread in vaccinated populations, as expected, but, taken with the promising results from other studies in South Africa using a similar viral vector, vaccines may continue to ease the toll on health care systems by preventing severe disease.”
Sarah Gilbert, Professor of Vaccinology at the University of Oxford said: “Efforts are underway to develop a new generation of vaccines that will allow protection to be redirected to emerging variants as booster jabs, if it turns out that it is necessary to do so.
“We are working with AstraZeneca to optimise the pipeline required for a strain change should one become necessary. This is the same issue that is faced by all of the vaccine developers, and we will continue to monitor the emergence of new variants that arise in readiness for a future strain change.”
Note: these findings are early preliminary data, which will be submitted for peer review and will appear as a pre-print in the days ahead.