Two-dose Covid-19 vaccine regimens do not induce enough neutralising antibodies against the Omicron coronavirus variant, British scientists found, indicating that increased infections in those previously infected or vaccinated may be likely.
Researchers from the University of Oxford published results on Monday from a study yet to be peer-reviewed, where they analysed blood samples from participants who were given doses from AstraZeneca-Oxford or Pfizer-BioNTech, in a large study looking into mixing of vaccines.
The results come a day after British Prime Minister Boris Johnson warned that two shots will not be enough to contain Omicron, following findings from the UK health agency last week that boosters significantly restore protection against the variant.
The Oxford study said that there was no evidence yet that the lower level of infection-fighting antibodies against Omicron could lead to higher risk of severe disease, hospitalisation or death in those who have got two doses of approved vaccines.
"These data are important but are only one part of the picture. They only look at neutralising antibodies after the second dose, but do not tell us about cellular immunity, and this will also be tested," said Matthew Snape, Oxford professor and co-author of the paper.