South Africa pauses Covid-19 vaccine rollout after disappointing AstraZeneca results

AstraZeneca’s vaccine did not provide significant protection against mild to moderate Covid-19 caused by the variant of the virus dominant in South Africa, researchers announced late on Sunday. 

The country has now paused its rollout of the vaccine as experts meet this week to discuss the data and how it will shape the country’s use of the jab.

The AstraZeneca vaccine was tested among about 1 750 healthy adults in South Africa. Half of those in the study were randomly assigned to receive the vaccine; the other half took a placebo of saline solution. Neither group knew which was which.

Jab initially showed 75% efficacy against mild-to-moderate Covid-19

By October 2020, less than a year after it started, the trial showed promising results.
The jab cut people’s risk of developing mild to moderate Covid-19 by 75%. But progress was short-lived.

Just less than two months later, South Africa entered its second wave of Covid-19 infections —  this time fuelled by a novel, faster-spreading variant of the virus.

Against this new foe, AstraZeneca’s vaccine was largely powerless to prevent mild to moderate Covid-19, says Shabir Madhi, the director of the Vaccines and Infectious Diseases Analytics Research Unit at the University of the Witwatersrand University. The findings, released in a presentation on national television, have been submitted for publication in a peer-reviewed journal and are currently being processed.

“Until the end of October, the AstraZeneca vaccine was showing tremendous potential in terms of reducing even mild and moderate cases,” Madhi says. “But, what is an unfortunate reality for viruses, bacteria and most other organisms is that they do mutate.” 

Viruses mutate commonly, creating new variants. Not all variants, however, change the way the virus spreads or affects people. The variant first discovered in South Africa has been shown to spread more quickly, but there is no evidence it causes people to become more sick.

What do you need to know about the AstraZeneca vaccine in South Africa?

  • The vaccine is safe to use, but did not show significant protection against mild or moderate Covid-19 when tested against the Covid-19 variant common in South Africa.
  • The South African AstraZeneca study could not tell scientists if the vaccine could protect against severe Covid-19, deaths or hospitalisation, because the sample size was too small, and people in it were largely healthy.
  • The trial could also not detect any protection against Covid-19 that was less than 60%. A vaccine that could halve a person’s risk of mild to severe Covid-19 for at least six months would meet the World Health Organisation (WHO) minimum vaccine requirements.

Still, Madhi says, there are limits to what the AstraZeneca vaccine trial could or couldn’t show. For instance, it wasn’t designed to detect any reductions in Covid-19 risk of less than 60%. And the AstraZeneca jab may yet still show promise in preventing severe Covid-19.  

How well does a Covid-19 vaccine need to be to help curb infections? 

Madhi says both United States and European drug regulators, as well as the WHO, say they’re looking for jabs to reduce people’s risk of Covid-19 by half, and for that protection to last at least six months. 

Variant first discovered in South Africa proves formidable for Covid-19 vaccines 

AstraZeneca’s findings come less than two weeks after Johnson & Johnson (J&J) issued a press release stating its one-dose Covid-19 vaccine reduced the risk of moderate to serious disease by about 57% in South African participants, despite the new variant

However, the jab performed better in the United States, reducing that same risk by 72%. Similarly, the Novavax vaccine was found to reduce HIV-negative people’s risk of mild to severe Covid-19 in South Africa by 60%. Still, it again was found to be more effective in the United Kingdom in the absence of the variant now dominating South African Covid-19 cases.

“We’ve now come to appreciate that not only is [the new variant] more transmissible,” Madhi says, “but that it also might be resistant to antibodies that have been induced by past infection … as well as antibodies that might be induced by many of the vaccines.”

Madhi cautions that although current vaccines were not specifically designed to address new variants, this is likely to change. United States pharmaceutical company Moderna is already studying a booster shot to improve its vaccine’s efficacy against the variant dominant in South Africa after lab tests showed the jab performed more poorly against the new variant, Stat news recently reported. 

The company has offered South Africa 20-million doses by May, according to activist Rehad Desai, who says he has seen leaked email correspondence between the government and Moderna. This comes after Moderna initially told the government it wasn’t interested in registering its vaccine for use in South Africa, Health Minister Zweli Mkhize said in December.

New results, new Covid-19 vaccine strategy?

The disappointing results from AstraZeneca’s trial in South Africa come a little more than a week after the country celebrated the arrival of one-million doses of the AstraZeneca vaccine. Mkhize says local and international scientists will review the evidence and advise the government how to use the jabs best.

Meanwhile, the country is expected to know in just days whether scientists working on the J&J vaccine trial can begin giving the jab to healthcare workers in the country as part of an expanded study, trial researcher and Medical Research Council president Glenda Gray says.

Although the J&J was 57% effective at preventing moderate to severe Covid-19 caused by the variant, it was even better at guarding against severe and critical Covid-19 cases across countries — variant or no variant, Gray explains. 

The J&J vaccine ultimately reduced a person’s risk of developing severe and critical Covid-19 by 85%, even when confronted by the new variant. The large, late-stage international trial of the vaccine also confirmed that the jab was safe.

In advocating for an expanded trial of the vaccine, scientists are likely balancing healthcare workers’ need for access to an effective vaccine shown to drastically reduce deaths with the need to collect more data on the jab.

This careful balancing act has led to similar clinical access programmes in the past to allow patients with extensively drug-resistant tuberculosis with no other options access to new treatments.

J&J has already applied to the US regulator, the Food and Drug Administration, to distribute the vaccine under emergency use provisions. Similar other applications are pending globally, Gray says.

J&J provides data on its vaccine regularly to the South African Health Products Regulatory Authority as part of a rolling review to help fast-track approvals. 

Meanwhile, time is of the essence for South Africa. The country’s current AstraZeneca vaccine stocks will expire in early April unless the provider, the Serum Institute of India, can either send new stock or advise South Africa it can safely extend the vaccine’s shelf life.

Almost out of its second wave, the country is also expecting a fresh wave of infections in three to four months, Madhi says.

“The question that we need to ask ourselves is: Knowing that both AstraZeneca and the J&J vaccine are safe … and even though there are question marks in terms of the effectiveness of the AstraZeneca vaccine against severe disease — do we want to take the risk of not vaccinating high-risk groups now knowing that you’re not going to cause harm, but they might be protected against severe disease?” Madhi says.

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Laura López González
Laura López González is a freelance health journalist and editor with more than 15 years of experience covering global health. She is the former deputy editor of South Africa's Bhekisisa Centre for Health Journalism.

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