DURBAN (BLOOMBERG, REUTERS) - The Omicron variant evades immunity induced by Pfizer-BioNTech's shot better than other coronavirus variants, according to laboratory experiments that indicate a booster shot could help stop the highly mutated virus.
In the first reported experiments gauging the effectiveness of the Pfizer-BioNTech vaccine, researchers at the African Health Research Institute found that Omicron infection results in about a 40-fold reduction in virus-blocking antibodies compared with the strain detected in China almost two years ago.
The loss of immune protection is "robust, but not complete", said Professor Alex Sigal, head of research at the Durban-based laboratory, in an online presentation of the first reported experiments gauging the effectiveness of the vaccine against the new variant late on Tuesday (Dec 7).
"There will be more breakthrough" of vaccine-induced immunity, he said. "A good booster probably would decrease your chance of infection, especially severe infection leading to more severe disease. People who haven't had a booster should get one, and people who have been previously infected should be vaccinated."
Representatives for Pfizer and BioNTech, makers of the first Covid-19 vaccine cleared in the US, did not immediately respond to a request for comment.
Last week, BioNTech chief executive Ugur Sahin said that "we think it's likely that people will have substantial protection against severe disease caused by Omicron".
The study may add to the debate over whether tweaked, Omicron-targeted vaccines will be needed soon to continue effectively fighting the pandemic.
Moderna President Stephen Hoge has said there's a risk that existing vaccines will be less effective against the strain, although US medical adviser Anthony Fauci said the severity of illness caused by the variant may be limited.
Since South Africa announced the discovery of Omicron on Nov 25, about 450 researchers globally have been working to isolate the highly mutated variant from patient specimens, grow it in the lab, verify its genomic sequence, and establish methods to test it in blood-plasma samples, according to the World Health Organisation (WHO).
Omicron's rapid spread in South Africa has raised concern that the immune protection generated by vaccination, or a previous bout of Covid-19, may be insufficient to stop infections or stem a fresh wave of cases and hospitalisations.
The WHO has warned that Omicron could fuel surges with "severe consequences" amid signs that it makes the coronavirus more transmissible.
Still, the jump in cases in South Africa following Omicron's emergence hasn't overwhelmed hospitals so far, prompting some cautious optimism that the new strain may cause mostly mild illness.
The work in Prof Sigal's lab involved testing blood plasma from people who were vaccinated against Covid-19 with the Pfizer-BioNTech shot to gauge the concentration of antibodies needed to neutralise or block the virus.
Levels of neutralizing antibodies against omicron were notably higher in a subset of participants who had a bout of Covid-19 about a year earlier, Prof Sigal said.
That's "promising", said Dr John Wherry, director of the institute for immunology at the University of Pennsylvania's Perelman School of Medicine. It likely means an additional dose of the currently available vaccines would boost levels of neutralising antibodies to Omicron, though more data is needed to confirm that, he said.
The results are preliminary and exact levels of immune escape may change, Prof Sigal said.
The results, along with those from other labs currently under way, will help determine whether or not existing Covid-19 vaccines need to be altered to protect against Omicron.
Prof Sigal's laboratory was the first to isolate the Beta variant, a strain of the coronavirus that was identified in South Africa in late 2020.
He noted that Omicron escapes antibody neutralisation more readily than Beta, which had been considered the most immune evasive of the variants of concern detected previously.