The Wits Vaccines and Infectious Diseases Analytics Research Unit, which runs the ChAdOx1 nCoV-19 vaccine trial in South Africa, has announced results

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 in mid-November 2020.

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 non-B.1.351 variants in South Africa. Researchers from South Africa and the 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, which will be 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 in those with prior infection.

In this study of approximately 2,000 volunteers where the median age was 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 low risk.

Work is already underway at the University of Oxford and in conjunction with partners to produce a 2nd 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. This could be relevant to the ChAdOx1 nCoV-19 vaccine, which has been developed using similar technology as the Janssen vaccine, and for which vaccine induced immune responses are also similar. ‘These findings also force us to recalibrate thinking about how to approach the pandemic virus and shift the focus from the aspirational goal of herd immunity against transmission to the protection of all at risk individuals in population against severe disease.’.