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South Africa concern

Questions over AstraZeneca vaccine’s efficacy against new variant.

South Africa has suspended the rollout of the AstraZeneca vaccine after a small-scale trial found that the vaccine offers only “minimal protection against mild-moderate COVID-19 infection” from the coronavirus variant (B.1.351) first identified in South Africa last December.

“This is preliminary data,” says Adam Taylor, a virologist and researcher at the Menzies Health Institute Queensland at Griffith University, Queensland. “This is a very small study, and the demographics are restricted.”

The study, yet to be peer-reviewed, involved only 2000 volunteers who were on average 31 years old.

Researchers from the University of Witwatersrand, South Africa, and the University of Oxford, UK, found that the AstraZeneca vaccine was highly effective against the original coronavirus strain in South Africa. But its potency was substantially reduced against the new B.1.351 variant. 

Consequently, the South African government had decided to wait for more scientific evidence before resuming AstraZeneca rollout. “It’s certainly wise to wait for more data,” says Taylor, “but what we do not see from this study is the effect on severe disease.” 

Current data show no evidence of a reduction in the AstraZeneca vaccine’s effectiveness in preventing severe disease. “And that is important, it’s what causes hospitalisation, it’s what leads to death from COVID-19,” adds Taylor.

While Australia is under less pressure to begin COVID-19 vaccination than other countries, the government has already ordered over 53 million doses of the AstraZeneca vaccine. The Therapeutic Goods Administration is expected to approve its use within days, but these new findings raise questions about Australia’s reliance on the AstraZeneca vaccine in the fight against COVID-19.

“It’s too early to say that we shouldn’t be using this vaccine,” says Taylor, “especially when previous studies have shown good efficacy, good safety, and the prevention of severe disease and mortality.”

While Taylor suggests there is no reason for alarm just yet, it is crucial to keep up with genomic sequencing. “We’ve got to keep eyes on how the virus is changing. And what will help with that is ongoing sequencing of the virus. That’ll also give us a good indication of how well vaccines work,” he says. 

Although it’s hard to draw definite conclusions from such a small study, these findings indicate that this coronavirus strain may find ways to continue to spread in vaccinated populations. But vaccines will prevent severe disease, helping ease the toll on health-care systems in countries where the pandemic is still out of control.

In a press release, professor of vaccinology at the University of Oxford Sarah Gilbert, the AstraZeneca vaccine’s lead researcher, said that the team is already working on a new generation of the vaccine adapted to target emerging variants.

Some of the other vaccine makers, such as Novavax, have also begun updating their vaccines to tackle the new variants. mRNA vaccines, such as those from Pfizer or Moderna, can be rapidly modified to add genetic sequences from these new variants. “Hopefully these updated vaccines can be used as boosters as the pandemic progresses,” says Taylor.

Manuela Callari

Manuela Callari

Dr Manuela Callari is a Sydney-based freelance science writer who specialises in health and medical stories.

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