Latest: China says its vaccines may have weaker antibody response against new strains
Inactivated vaccines may be more effective against fighting new mutated strains of the coronavirus, according to a top immunologist.
Such vaccines, including the UAE-approved Sinopharm, use a “dead” version of the whole virus, offering protection against multiple areas.
That means they may hold up better against variants.
Luke O’Neill, professor of biochemistry in the School of Biochemistry and Immunology at Trinity College Dublin, said because inactivated vaccines are based on the whole virus, the immune system will have “lots of weapons against lots of parts of the vaccine”.
Several vaccines have now been approved against Covid-19.
Most of them, including Pfizer-BioNTech, Moderna, Oxford-AstraZeneca and Russia’s Sputnik V, target the spike protein on the surface of the coronavirus, which the virus uses to enter cells.
Covid-19 variants which have emerged in recent months in the UK, South Africa and Brazil include a number of mutations in the spike, which experts said may render the vaccines less effective.
"The other vaccines are just against the spike protein so if that mutates and escapes the immune system, the vaccines may not work as well," Prof O'Neill told The National
“The whole virus vaccines are very likely to work against any variant.”
He said it was not yet clear how much the spike vaccines will be affected by variants.
“And there are signs that the Pfizer vaccine might still generate antibodies against the UK variant, at least,” he said.
“Also there might still be a good T cell response with the Pfizer and other vaccines.”
Sinopharm and other inactivated vaccines are also expected to generate a T-cell response, he said.
At the weekend, White House health advisor Dr Anthony Fauci warned the Pfizer and other spike protein vaccines may not be as effective in guarding against new variants.
That is a concern as two that have emerged in the UK and South Africa are believed to be more transmissible and could even have higher mortality rates.
Early research, which has yet to be peer reviewed, backed Dr Fauci’s claim.
The study, published on bioRxiv, a website on which authors can share early findings, said the variant identified in South Africa, known as 501Y.V2, can evade antibodies provided by treatments. It may reduce the efficacy of some of the current vaccines, it said.
“Furthermore, 501Y.V2 shows substantial or complete escape from neutralising antibodies in Covid-19 convalescent plasma,” researchers with South Africa’s National Institute for Communicable Diseases wrote.
Their findings highlight the prospect of reinfection “and may foreshadow reduced efficacy of current spike-based vaccines”, they wrote.
The Pfizer-BioNTech, Moderna, Oxford-AstraZeneca and Russia’s Sputnik V vaccines issue instructions to the body to make its own version of the spike, which triggers antibodies against the virus.
But the spike is just one protein that forms the overall structure of the virus. There are in fact four: the spike, envelope (E), membrane (M) and nucleocapsid (N).
Inactivated vaccines likely target all four areas, researchers said.
Researchers have discovered that people who have been infected with SARS-Cov-2 make more antibodies against the N protein than the spike.
Their role in protecting people from infection is not fully understood, but they are likely to play a role and should be targeted by later generations of vaccines, they said.
"Future vaccines will probably focus on more than just the spike protein of Sars-CoV-2, and the N protein is a promising target to add to the current strategies being considered," Dr Sarah Caddy, an immunologist at the University of Cambridge, wrote in The Conversation.
Speaking on Irish radio last week, Prof O’Neill said he was not overly concerned by the new variants, but they require close monitoring.
“The worry would be if there are extra variants, another strain arises,” he told Radio One.
Many of the vaccines in development target the virus spike, but not all.
There are three inactivated vaccines in China in phase 3 trials, and another in India.
Several are in phase 1 and 2 phase trials, including another “worth watching”, said Prof O’Neill, by Valneva, a European manufacturer, which will produce the inactivated vaccine in Scotland.
It is currently undergoing a trial in the UK, which has ordered 60 million doses.
