Jakub Porzycki | NurPhoto | Getty Images
LONDON – Two doses of Oxford-AstraZeneca or Pfizer-BioNTech Covid-19 vaccines are significantly less effective at repelling the omicron than previous versions of the coronavirus, scientists have found.
However, the researchers were optimistic that the booster injection would improve immunity against the new, highly hereditary variant.
In a new study, announced Monday, researchers at the University of Oxford tested blood samples from people 28 days after taking the second dose of either vaccine.
When the omicron was injected into these samples, the scientists reported a “significant drop” in neutralizing antibodies that fight Covid, compared to the immune responses seen against earlier variants.
The research paper noted that some vaccine recipients “were unable to neutralize [the virus] generally.”
“This is likely to lead to an increase in the number of breakthrough infections in previously infected or double-vaccinated individuals, which could trigger a new wave of infection, although there is currently no evidence of an increased potential to cause serious illness, hospitalization or death,” the study authors said.
A pre-press study that has not yet been peer-reviewed was published on the MedRxiv server.
Gavin Screaton, head of the Department of Health Sciences at the University of Oxford and lead author of the article, said in a press release Monday that the results should “make it clear that those who are offered the booster should take it.”
“While there is no evidence of an increased risk of severe illness or death from the virus among the vaccinated population, we must remain cautious as more cases continue to place a significant burden on health systems,” he warned.
“Vaccinations stimulate many parts of our immune system, including neutralizing antibodies and T cells,” added study co-author Theresa Lamb, professor of vaccinology at the University of Oxford.
“Real-world efficacy data has shown us that vaccines continue to protect against severe disease with previous options of concern. The best way to protect us in this pandemic is to get vaccines in service. “
A report released by the UK Health Safety Agency on Friday said the two doses of the Covid vaccine were significantly less effective in preventing symptomatic illnesses caused by the omicron variant infection compared to the delta vaccine. However, the report notes that after booster vaccination, vaccines were considered 70–75% effective in preventing symptomatic infections.
“In previous versions, the vaccine was more effective against serious illnesses, including hospitalization and death, than against mild illnesses,” the UKHSA said in a statement. “It will take several weeks before the effectiveness of Omicron can be assessed for severe illness, but based on this experience, it is likely to be significantly higher than for symptomatic illness.”
In a televised statement on Sunday, British Prime Minister Boris Johnson warned Britain would face a “tidal wave” of Omicron infections and announced the country would be accelerating its revaccination program to offer all adults a third dose of the vaccine by the end of the year. The government previously planned to extend its pressure boosting scheme to everyone over 18 by the end of January.
Johnson’s announcement came after chief healthcare professionals in England, Scotland, Wales and Northern Ireland raised the UK coronavirus threat to four – the second-highest – in light of the spread of the omicron.
Elsewhere, an Israeli study published Saturday showed that a three-dose course of Pfizer-BioNTech vaccine offered significant protection against the omicron variant. In July, Israel began its revaccination program.
The findings from Israel came after researchers in South Africa discovered that omicron could partially evade immunity from two vaccines of the Pfizer-BioNTech vaccine.
The omicron variant, considered more infectious than its delta predecessor, was first discovered in South Africa in November and has since spread to at least 38 countries around the world and 25 US states.