Weakest AstraZeneca Covid-19 vaccine against South African strain

The trial, which involved about 2,000 volunteers with a median age of 31, was too small and its participants too young to draw broad conclusions about the vaccine’s overall effectiveness in protecting against coronavirus disease, especially when it comes to hospitalizations or death. However, their findings contribute to concerns that a mutant virus is making existing Covid-19 vaccines less effective and that vaccines will need to be updated to protect against new strains of viruses.

Johnson & Johnson and Novavax Inc.,

whose vaccines have not yet been authorized in any country, also found that their vaccines were less effective in recent human clinical trials in South Africa. But their vaccines were still considered 50% or more effective in preventing mild or moderate cases of Covid- 19 and even more powerful in protecting recipients from serious illness and hospitalization due to the new strain.

Sunday’s press release on the AstraZeneca study in South Africa did not provide an efficacy rate for the vaccine. The Johnson & Johnson test in South Africa included about 6,500 people, while Novavax’s test had 4,400.

The University of Witwatersrand in Johannesburg, which conducted the AstraZeneca trial, said it could not assess whether the vaccine provided protection against more severe cases of Covid-19, because the relatively young trial participants were at low risk of developing severe Covid-19 symptoms.

Still, the chief investigator for the South African trials and the University of Oxford scientists who developed the AstraZeneca vaccine said that, based on the results of other vaccine trials, they were optimistic that their injection would provide protection against Covid- 19 serious.

“This study confirms that the pandemic coronavirus will find ways to continue to spread in vaccinated populations, as expected,” said Andrew Pollard, director of the Oxford Vaccine Group at the University of Oxford, in the press release on the results of the trial. “But, with the promising results of other studies in South Africa using a similar viral vector, vaccines can continue to lessen the impact on health systems by preventing serious illnesses.”

An AstraZeneca spokesman said the company believes that “our vaccine can protect against serious illnesses”.

The South African strain, known as B.1.351, is already responsible for most infections in South Africa and has been responsible for a sharp increase in Covid-19 cases in countries like Mozambique and Zambia in recent weeks.

Researchers in the United States, Canada, Israel and several European and African countries have also detected the virus in positive coronavirus test samples from people with no recent travel history, suggesting that it is spreading in the community. In total, it has been identified in 32 countries and virologists say it is likely to be present in others that do not systematically sequence positive test samples.

Scientists in South Africa and the United Kingdom believe that the B.1.351 strain is about 50% more contagious than previous versions of the virus based on the much faster increase in Covid-19 infections during the second wave of South Africa. South compared to the first and biological studies of changes in the structure of the virus.

South African researchers said that variant B.1.351 does not appear to lead to more deaths or more serious cases of Covid-19.

Ravi Gupta, a professor of clinical microbiology at the University of Cambridge who was not involved in the South African AstraZeneca vaccine trial, said Sunday’s results underscored the need to update the current Covid-19 vaccine crop against the new variants. Still, he said, he hopes AstraZeneca’s shots will still provide some protection against the new strain. “We definitely still need to use vaccines to protect people from serious illness,” he said.

Concern about the South African variant and its impact on vaccine effectiveness is centered on a mutation known as E484K. The researchers believe that this mutation makes it more difficult for antibodies to control and neutralize the virus.

The same mutation was also found in a separate variant discovered in Brazil. Researchers in the UK said earlier this month that they found the E484K mutation in a small number of patients infected with another variant of the rapidly spreading coronavirus that is causing infections there.

—Jenny Strasburg contributed to this article.

Write to Gabriele Steinhauser at [email protected]

Corrections and amplifications
Volunteers in a South African study with AstraZeneca’s Covid-19 vaccine had an average age of 31 years. An earlier version of this article incorrectly stated that they had an average age of 32.