South Africa Pauses Use of AstraZeneca COVID-19 Vaccine, Saying It Is Ineffective Against Variant


Investigators are working to create a second generation of the vaccine, adapted to target variants with mutations similar to those found in South Africa.

South Africa has put its use of Oxford and AstraZeneca’s coronavirus disease 2019 (COVID-19) vaccine on hold, after findings suggested minimal protection against mild-to-moderate infections with the variant now dominant in the country.

According to a press release from the University of Oxford, a 2-dose regimen of the ChAdOx1 COVID-19 vaccine provided minimal protection against mild-to-moderate infection caused by the B.1.351 variant first found in South Africa.1 The strain has multiple variations in the spike protein, and although there is currently no evidence suggesting that it impacts disease severity, some evidence shows that the spike protein mutations may affect neutralization by some polyclonal and monoclonal antibodies.2

In the new analysis, which was submitted as a pre-print prior to peer-review publication, investigators from the University of Witwatersrand and others found that viral neutralization by sera induced by the ChAdOx1 vaccine against the B.1.351 variant was substantially reduced compared to the original strain of COVID-19. The early data have been submitted for peer review, and the press release said the findings seem to confirm the theory that mutations in the virus seen in South Africa will allow ongoing transmission even in vaccinated populations.1

The study included approximately 2000 volunteers at an average age of 31 years. Mild disease was defined as at least 1 symptom of COVID-19, and the press release said they were not able to assess protection against mild-to-moderate disease, hospitalization, or death because the target population was at such low risk.1

According to the press release, investigators are working to create a second generation of the vaccine, adapted to target variants with mutations similar to B.1.351.1 In a statement, chief investigator of the trial Shabir Madhi, PhD, said recent data from other studies suggest that protection against more severe disease may still be effective with the vaccine.1

“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,” Madhi said in the press release. “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.”1

According to reporting by Reuters, the South African government is waiting for advice from scientists on how to proceed. The country hopes to vaccinate 40 million people in order to achieve some level of herd immunity, but it had yet to administer a single vaccine as of Sunday.3 It will begin offering the Johnson & Johnson and Pfizer/BioNTech vaccines to health workers in the coming weeks.3

“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,” said Andrew Pollard, chief investigator of the Oxford vaccine trial, in a press release.1


  • ChAdOx1 n-Cov-19 provides minimal protection against mild-moderate COVID-19 infection from B.351 coronavirus variant in young South African adults [news release]. University of Oxford; February 7, 2021. Accessed February 8, 202
  • Antrim, A. COVID-19 Variants Raise New Questions About Vaccines. Pharmacy Times; February 4, 2021. Accessed February 8, 2021.
  • Winning A, Kumwenda-Mtambo O. South Africa puts AstraZeneca vaccinations on hold over variant data. Reuters; February 8, 2021. Accessed February 8, 2021.

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