A preprint of ongoing work to assess effectiveness of Oxford’s ChAdOx1 coronavirus vaccine shows that the existing vaccine has similar efficacy against the B.1.1.7 ‘Kent’ coronavirus strain currently circulating in the UK to previously circulating variants.
The Oxford University researchers who developed the ChAdOx1-nCoV 19 vaccine have found that it remains effective against one of the new variants of the disease.
The preprint also describes recent analysis showing that vaccination with ChAdOx1 nCoV-19 results in a reduction in the duration of shedding and viral load, which may translate into a reduced transmission of the disease.
Andrew Pollard, Professor of Paediatric Infection and Immunity, and Chief Investigator on the Oxford vaccine trial, said:
‘Data from our trials of the ChAdOx1 vaccine in the United Kingdom indicate that the vaccine not only protects against the original pandemic virus, but also protects against the novel variant, B.1.1.7, which caused the surge in disease from the end of 2020 across the UK.’
Sarah Gilbert, Professor of Vaccinology, and Chief Investigator on the Oxford vaccine trial, said:
‘All viruses accumulate mutations over time, and for influenza vaccines there is a well-known process of global viral surveillance, and selection of strains for an annual update of the vaccines.’
Between 1 October 2020 and 14 January 2021, the researchers used swabs taken from volunteers with both symptomatic and asymptomatic infection enrolled in a phase II/III vaccine efficacy study to work out which strain of coronavirus they had been infected with after receiving either the vaccine or the control.
The protection against symptomatic infection was similar despite lower neutralising antibody titres in vaccinated individuals against the B.1.1.7 variant than the 'Victoria’ strain of virus.
These are the first findings regarding the efficacy of the Oxford vaccine against new variants. Vaccine researchers are already looking at ways to modify the existing vaccines quickly and simply to protect against new variants.
Professor Gilbert continued:
‘Coronaviruses are less prone to mutation than influenza viruses, but we have always expected that as the pandemic continues, new variants will begin to become dominant amongst the viruses that are circulating and that eventually a new version of the vaccine, with an updated spike protein, would be required to maintain vaccine efficacy at the highest level possible
‘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, supplied as a pre-print for information prior to undergoing the peer review process.