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| A South African health worker receives the Johnson and Johnson coronavirus disease (COVID-19) vaccination at the Khayelitsha Hospital near Cape Town, South Africa, Feb. 17, 2021. Reuters |
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In a non-peer-reviewed study published last week, a team in Boston found a drop in the amount of the mutated South Africa strain neutralised by antibodies induced by the Pfizer-BioNTech and Moderna vaccines of between 75 and 97-fold. The drop was 13-fold against another strain circulating in Brazil.
"Strikingly, neutralisation of all three South African B.1.351 strains was substantially decreased," the researchers said.
Similar trends were reported by researchers in Germany and the US National Institutes of Health.
The lead scientist of the Boston study, Alejandro Balazs from the Ragon Institute of MGH, MIT, and Harvard, said authorities should monitor cases to "ensure that we have a clear view of which variants are responsible for new infections".
"I believe several companies have already announced that they would begin development of an updated booster shot," Balazs said in the paper published on preprint platform medRxiv.
The Pfizer-BioNTech and Moderna vaccines use mRNA technology, which has so far had the best results against Covid-19.
Clinical trials showed that their protection rates exceeded 90 per cent, higher than any other types of vaccines on the market.
In many areas around the world including Hong Kong, the mRNA shots are a major part of vaccine roll-out plans.
Benjamin Neuman, a virologist and professor of biology at Texas A&M University, said the three papers indicated that "immunity built with the currently available vaccines is less effective at blocking infection by the South Africa and Brazil variants of Sars-CoV-2", the virus that causes Covid-19.
"This is certainly not good news," said Neuman, who was not involved in any of the studies.
"All of the major approved vaccines based on the spike protein, including Moderna, Pfizer, AstraZeneca, Sputnik V and CanSino, and the upcoming Johnson&Johnson, Novavax and Sanofi vaccines use the same stabilised version of the spike that was circulating in late 2019.
"The concern with basing so many vaccines on the same variant is that a virus that can escape one vaccine, can likely escape all of them."
The B.1.351 variant is of particular concern.
It was first detected in communities near Cape Town where herd immunity was believed to have established after the first wave of infection.
Researchers in South Africa said the B.1.351 variant might have found new ways to evade the human immune system by evolving continuously in the region's large HIV-positive population.
The variant has spread to many countries including Britain and the United States.
In South Africa, health authorities have halted plans to vaccinate its people with 1 million doses of the AstraZeneca vaccine because of "disappointing" results against the strain.
But scientists said people should still get the vaccine when it became available.
"Anyone deciding whether to take the vaccine today should keep in mind that they have been demonstrated in several trials to very significantly reduce cases of severe disease. None of the studies published so far, including ours, has questioned the efficacy of these vaccines," Balazs said.
"There are good reasons to believe that even if neutralisation were reduced, there are other protective mechanisms which could still protect against severe disease."
Neuman agreed, saying the reduced potency might only affect a small amount of antibodies that stop the virus from entering cells.
"There are lots of ways for the immune system to recognise Sars-CoV-2, and nearly all of those are identical, no matter the variant," he said.
"Even if a vaccinated person should become infected with a variant, the other components of immunity should still lead to shorter and milder illnesses."
Major drug companies including Pfizer and Moderna are working on upgraded versions based on emerging variants.
The mRNA vaccines are thought to take less time to alter but it is still not known when they will become available to the general public.
"Since the starting pool of effective antibodies would be reduced, people would likely need to be revaccinated sooner in order to stay protected," Neuman said.
