South Africa Halts AstraZeneca COVID-19 Vaccine Rollout Amid Concerns Over Efficacy Against B.1.351 Variant

Compiled by Keke

Recently, according to foreign media reports, South Africa has postponed the rollout of the AstraZeneca/Oxford University COVID-19 vaccine, as data indicates that the vaccine “provides only minimal protection” against mild cases caused by the South African variant B.1.351. This data was released by the Wits Vaccine and Infectious Disease Analytics (VIDA) research unit, which is conducting COVID-19 vaccine trials in South Africa. These findings are yet to undergo peer review.

Currently, the actual efficacy against severe COVID-19 infection for the South African variant has not been assessed, but the AstraZeneca vaccine demonstrates high efficacy against the original non-B.1.351 variants in South Africa. This study indicates that the AstraZeneca/Oxford vaccine neutralizes the virus, with a significant reduction in efficacy against the B.1.351 variant compared to the original “wild-type” strain originating from China.

This study enrolled approximately 2,000 volunteers with a mean age of 31 years. Mild disease was defined as the presence of at least one COVID-19 symptom. As the study targeted a low-risk population, it was unable to assess efficacy against moderate-to-severe disease, hospitalization, or death.

Oxford University and AstraZeneca are already developing a next-generation vaccine that, if necessary, will be modified to target the South African B.1.351 variant.

Shabir Madhi, Professor of Vaccinology at the University of the Witwatersrand, Director of VIDA, and Principal Investigator for the South African trial, pointed out: “The latest data from a study initiated by Janssen in South Africa indicate that the study assessed moderate to severe disease rather than mild disease, demonstrating protection against these important disease endpoints. The study used a similar viral vector. This may be relevant to the ChAdOx1 nCoV-19 vaccine (AstraZeneca/University of Oxford vaccine), which was developed using technology similar to that of the Janssen vaccine and induces a comparable immune response.”

Maddi added, “These findings also compel us to recalibrate our approach to the COVID-19 pandemic, shifting the focus from the ideal goal of achieving population immunity to prevent transmission to protecting all high-risk groups within the population from severe disease.”

Two virologists advising the South African government stated at a press conference, “South Africa’s suspension of vaccine rollout is necessary so that the government can establish a new protocol aimed at ensuring that each vaccine reduces the burden of COVID-19 in South Africa.”

Salim Abdool Karim, an epidemiologist at Columbia University and a member of the South African government’s advisory committee, stated, “The rollout of the AstraZeneca vaccine needs to be temporarily halted so that we can obtain data on its clinical efficacy, and we need to adopt a new rollout strategy.”

News of the suspension of promotions has heightened concerns about the South African variant B.1.351. The AstraZeneca vaccine has not yet been authorized for use in the United States, and if its rollout is paused in South Africa, it seems unlikely to be used in the U.S. within the next few months. The vaccine has received authorization for use in the UK and the EU but has not yet submitted an approval application in the U.S. In the UK, South Africa, and Brazil, the vaccine demonstrated 76% efficacy after a single dose; after the second dose administered three months later, the vaccine's efficacy increased to 82%.

The U.S. Food and Drug Administration (FDA) is awaiting the completion of U.S. clinical trials. AstraZeneca stated that the trials would conclude “within the next one to two months.”

This delay was at least partly linked to a clinical trial hold in November 2020, when a UK patient who had received the vaccine developed partial spinal paralysis, potentially related to the vaccine. Although clinical trials resumed quickly thereafter in the UK and other countries (such as Brazil), trials in the United States were delayed by several weeks while the U.S. FDA evaluated the data.

Further questions remain regarding the research data from AstraZeneca and the University of Oxford. In one cohort of the trial, participants inadvertently received a half dose for the initial injection; this group demonstrated an efficacy of up to 90%, compared with 62% in the full-dose group. This discrepancy remains to be explained. Other unresolved issues include the vaccine’s efficacy in individuals aged 65 years and older.

Ashish Jha, Dean of the Brown University School of Public Health, believes that the U.S. FDA’s decision to await clearer data from U.S. clinical trials is a reasonable one under normal circumstances. However, a pertinent question arises: Are the current research findings and data reflective of normal circumstances?

According to AstraZeneca’s previous announcement, data from the Phase III UK trial have been shared with the U.S. FDA, and the vaccine authorization application will be submitted once data from the U.S. trials become available. The drug regulatory agencies in Germany and France have stated that there is currently insufficient evidence to justify vaccination of individuals aged 65 and older; therefore, they are limiting vaccination to those under the age of 65.

Early observations of the research data behind the suspension of rollout in South Africa do not clearly demonstrate issues with the vaccine. These data are limited to a small number of patients and may be insufficient to draw conclusions. Madhi pointed out that before the B.1.351 variant became more prevalent in South Africa, the AstraZeneca/Oxford University vaccine showed a trend of reducing mild COVID-19 cases by 75%. However, with the emergence of the variant, this figure dropped significantly, showing only a 22% reduction based on 42 symptomatic COVID-19 cases. Nevertheless, this finding is also unreliable, as the 95% confidence interval for the 22% efficacy estimate ranges from -50% to 60%.

AstraZeneca maintains that the vaccine can still prevent severe disease caused by infection with the South African variant, although current studies do not provide evidence in this regard.

Reference Source: South Africa Pauses AstraZeneca Vaccine Rollout Over Small but Dismal Study Results