Natural infection – and vaccines – generate a very wide variety of antibodies,each designed to attach themselves to a different part of the virus.
Antibodies that stick to COVID-19’s spike – the cellular harpoon SARS-CoV-2 uses to bind to human cells – are key,because they can block the virus from infected cells.
Changes to the shape of the virus’ spike can render some of those antibodies unable to stick.
But that does not mean the vaccine will become ineffective;a virus would require many,many changes to fully escape antibodies.
“We’re not focussing on a single molecule on the spike,” said Professor Trevor Drew,director of the Australian Centre for Disease Preparedness.
“All the information we have so far,both from our own work and from information in the UK and elsewhere,says at the moment the vaccine efficacy is unlikely to be affected.”
A woman waits to be tested for COVID-19 in a shopping centre car park in Johannesburg.Credit:AP Photo/Jerome Delay
Onestudy,posted on January 19 by a team led by scientists from the Rockefeller University in New York,looked at antibody responses to a virus bearing the variant’s mutations in 20 patients who had received either the Pfizer or Moderna vaccine.
It found vaccine-induced antibodies effectively neutralised viruses with the same mutations as B.1.1.7,the variant first spotted in Britain,and 501Y.V2,the variant first spotted in South Africa.
“The fact that neutralising activity is retained is encouraging,” said University of Sydney professor of medical microbiology James Triccas.
“Our focus should now be on next generation vaccines,in particular developing platforms that allow us to ‘pivot’ quickly to combat new variants.”
Vaccine researcher Professor James Triccas in a lab at Sydney University.Credit:Nick Moir
A second paper,led by the University of Cambridge’s Ravindra Gupta,looked at blood from 15 patients who had been given the Pfizer vaccine and also found modest reductions in vaccine effectiveness against a virus with B.1.1.7’s mutations.
“Vaccines will be impacted by variants,” Professor Gupta said, “though not for most individuals or at population level unless more mutations accrue.”
And athird study,published by Moderna’s own scientists on Monday,found B.1.1.7 did not cut the vaccine’s power. The South African strain moderately reduced it,but the vaccine was still able to neutralise the virus. In astatement,the company said it would start developing a “booster shot” that could cover the new variant.
A vial of the Pfizer-BioNTech COVID-19 vaccine.Credit:Bloomberg
“This is not surprising and this is the normal behaviour of viruses,to mutate and escape,” said Victoria University immunologist Professor Vasso Apostolopoulos.
“For example,the flu vaccine is updated every year to include mutated variants of the virus.”
A fourthstudy looked at 501Y.V2,or B.1.351,as the variant first spotted in South Africa is also known.
That virus is raising the most concern among scientists because it includes nine changes to its spike protein. A variant spotted in Brazil bears similar changes.
In tests on the blood of 44 patients who had recovered from COVID-19,21 had no detectable neutralising antibodies to 501Y.V2.
However,patients who had higher levels of natural immunity were much more likely to generate neutralising antibodies to 501Y.V2,suggesting a vaccine that produces a strong immune response might still cover the virus.
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“The current vaccines are expected to still be effective but with time – hopefully years – we will likely need second generation vaccines that are more effective against new variants,” said Professor Brendan Crabb,director of the Burnet Institute.
Based on that,he said governments everywhere should be working to quickly vaccinate the population,alongside using standard control measures,such as testing and tracing,to push infection numbers down.
“Remember,the more virus there is,the faster variants will arise,” he said.
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