South Africa (SA) has put its planned roll-out of AstraZeneca(AZ)/Oxford University’s COVID-19 vaccine on hold after new study results showed that the jab provides ‘minimal’ protection against the SA variant.
The study, conducted by researchers from the University of Witwatersrand and Oxford University, found that a two-dose regimen of the vaccine – also known as ChAdOx1 nCoV-19 – provides only minimal protection against mild-to-moderate COVID-19 caused by the SA or B.1.351 variant.
The research included approximately 2,000 volunteers with mild disease, which is defined as having at least one symptom of COVID-19.
The study did not assess the AZ/Oxford vaccine’s ability to protect against moderate-to-severe disease caused by the SA variant.
The early data, which has not yet been peer reviewed, seems to support the theory that mutations in the virus observed in the SA variant will enable ongoing transmission in vaccinated populations.
“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 healthcare systems by preventing severe disease,” said Andrew Pollard, chief investigator on the AZ/Oxford vaccine trial.
The researchers noted that Oxford University is already working on developing a second-generation vaccine that will be adapted to target variants of COVID-19 with mutations similar to B.1.351.
Following the publication of the pre-print study results, South African Health Minister Zweli Mkhize announced that the plans to roll out the vaccine in the country will be halted.
She added that the government will seek advice from experts on how to proceed with the vaccination programme going forward.
AZ has said that it is confident that its vaccine will be able to offer protection against serious illness, and this will help to ease the burden health systems are currently facing.
The company also found that the vaccine is effective against the COVID-19 variant that is currently dominant in the UK – also known as the B.1.1.7 variant.
Pfizer/BioNTech have found that the SA variant has a ‘small effect’ on their vaccine.
Researchers from Pfizer and the University of Texas Medical Branch (UTMB) noted that neutralisation against the virus with the three key mutations present in the SA variant was ‘slightly lower’ when compared to the other evaluated viruses.
Moderna has also announced that its COVID-19 vaccine appears effective against both the UK and the SA variants.
Researchers found that the Moderna COVID-19 vaccine produced neutralising antibodies that protect against both the UK and the SA variants.
In the early laboratory study, researchers observed no significant impact on antibodies with the UK variant, relative to prior variants.
However, Moderna noted that there was a six-fold reduction in neutralising antibodies observed with the SA strain, although the company added that the levels induced by its vaccine should still offer protection.