Pfizer has said a booster dose of its COVID-19 vaccine was able to neutralise the new Omicron variant in lab studies, even though the initial two doses appear significantly less effective.
The announcement on Wednesday is the first official statement from vaccine manufacturers on the efficacy of current shots against Omicron.
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Pfizer and its partner BioNTech said that lab tests showed a booster dose increased by 25-fold the level of so-called neutralising antibodies against Omicron. Their results have not been peer-reviewed.
According to the early laboratory research using blood serum from vaccinated people, a booster third dose generated around the same level of antibodies against Omicron as is seen after a second dose with other variants.
Scientists have speculated that the high jump in antibodies that comes with a third dose of COVID-19 vaccines might be enough to counter any decrease in effectiveness.
Antibody levels predict how well a vaccine may prevent infection with the coronavirus but they are just one layer of the immune system’s defences. Pfizer said two doses of the vaccine may still induce protection against severe disease.
“Although two doses of the vaccine may still offer protection against severe disease caused by the Omicron strain, it’s clear from these preliminary data that protection is maximised with a third dose of our vaccine,” Pfizer CEO Albert Bourla said in a statement.
“Ensuring as many people as possible are fully vaccinated with the first two dose series and a booster remains the best course of action to prevent the spread of COVID-19,” Bourla said.
The companies also said an Omicron-specific version of their coronavirus vaccine, which is currently under development, would be available by March.
The findings are broadly in line with a preliminary study published by researchers at the Africa Health Research Institute in South Africa on Tuesday, saying that Omicron can partially evade protection from two doses of the Pfizer-BioNTech vaccine. The findings also suggested that a third shot might help fend off infection.
The detection of the first Omicron cases two weeks ago coincided with a spike in infection numbers across the world.
The variant has fuelled concerns about a global COVID-19 resurgence.
Omicron has so far been found in 57 countries, according to the World Health Organization, with many reimposing travel restrictions to stem the spread.
No deaths have yet been associated with the variant, with some health officials saying that while Omicron may be more contagious than previous variants, early signs suggest it may cause less severe disease.