What we know about Oxford University/AstraZeneca Covid-19 vaccine and the South African variant
The Oxford University/AstraZeneca vaccine provides only “minimal protection” against mild to moderate Covid-19 infection from the South African variant, a study has shown, but there is hope that it may still offer life-saving protection against it.
The findings, which have yet to be peer-reviewed, appear to confirm the theory that mutations seen in this variant will allow ongoing transmission of the virus in vaccinated populations.
Oxford University and AstraZeneca are now working on a new generation of vaccines that would offer protection against the emerging variants, which could be given as booster jabs if required.
The research did not assess whether the vaccine would prevent the variant causing severe Covid-19 infection, hospitalisation or death because the 2,000 volunteers in South Africa involved, who had an average age of 31, were at such low risk.
But there are grounds for hope that the vaccine could still provide life-saving protection against the variant, which has been detected in more than 100 cases in the UK.
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, added: “Efforts are under way 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.”
A pre-print of the study can be read online.
The B.1.351 coronavirus variant - often referred to as the South Africa variant, as it first emerged there - is not currently dominant worldwide. But it is the dominant variant in the Eastern and Western Cape provinces of South Africa, and has been reported in at least 20 other countries, including the UK, US, Austria, Norway and Japan.
On February 2, the government said it had identified 105 cases of the South Africa variant and 11 of these could not be traced to travel from South Africa.
A new ‘surge testing’ regime is being carried out to track the variants in the UK, with positive cases sequenced for genomic data. Everyone over the age of 16 is being asked to take a coronavirus PCR test - booked in the usual way - in the following locations:
- East of England - EN10 (Broxbourne)
- London - W7 (Ealing), N17 (Haringey) and CR4 (Mitcham)
- West Midlands - B31 (Birmingham, WS2 (Walsall), WR3 and some people in WR9 ( both Worcester)
- South East - ME15 (Maidstone) and GU21 (Woking)
- North West - PR9 (Southport)
- Worcestershire WR3
- an area in Sefton PR9
- areas in Bristol and South Gloucestershire.
The UK leads the world in genomic surveillance of the virus and has contributed more than half the world’s Covid-19 genome sequences, thanks to the efforts of the Cambridge-led Covid-19 Genomics UK (COG-UK) Consortium.
Such surveillance has identified that a mutation - known as E484K - to the virus’ spike protein, is present in the South African variant. But it has also been found in some samples of other variants, including the UK’s fast-spreading Kent variant (B.1.1.7) and the Brazilian (B.1.1.28) variant.
Additional contact tracing, laboratory analysis and testing is being carried out in areas where this mutation has been detected, which include Bristol and Liverpool.
This ‘escape mutation’ helps the virus evade the body’s immune defences
Preliminary data from a University of Cambridge study using the Pfizer/BioNTech vaccine has shown that almost a tenfold increase in antibodies was required to neutralise this mutation. For those aged over 80, this was only achieved after the second dose of the vaccine was delivered, the study found.
In research published on Friday, University of Cambridge scientists warned that mutations similar to those in the B1.1.7 UK variant could also arise in cases of chronic infection, where treatment over an extended period could provide the virus multiple opportunities to evolve.
Meanwhile, another highly infectious variant, P.1, has been present in Brazil since mid-2020 and was the cause of the surge in infections that hit Manaus so hard.
There was better news, however, from the preliminary findings of Phase III clinical trials in the UK, Brazil and South Africa on the Oxford University/AstraZeneca vaccine.
It found the vaccine was safe and effective at preventing Covid-19, with no severe cases and no hospitalisations, more than 22 days after the first dose.
The vaccine efficacy was deemed to be 76 per cent after one dose, with this protection maintained after a second. Delaying the second dose for 12 weeks or more actually led to an increase in this effectiveness to 82 per cent. This was good news for the UK’s vaccine roll-out, as second doses here are being administered after up to 12 weeks.
Encouragingly, the analysis also suggested the vaccine appeared to reduce asymptomatic transmission of the virus by 67 per cent after one dose and 50 per cent after two.
The findings can be read in the Lancet.