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Two-dose vaccines induce lower antibodies against Omicron — Oxford study

Two-dose COVID-19 vaccine regimens do not induce enough neutralising antibodies against the Omicron coronavirus variant, British scientists have found, meaning that increased infections in those previously infected or vaccinated might be likely.

Researchers from the University of Oxford published results on Monday (13 December) 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, reports Reuters, came a day after British Prime Minister Boris Johnson warned that two shots would not be enough to contain Omicron, after findings from the UK health agency last week that boosters significantly restore protection against the variant.

The Oxford study said 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.

Study details

Reduced neutralisation of SARS-COV-2 Omicron-B.1.1.529 variant by post-immunisation serum

Wanwisa Dejnirattisai, Robert Shaw, Piyada Supasa, Chang Liu, Arabella Stuart, Andrew Pollard, Xinxue Liu, Teresa Lambe, Derrick Crook, Dave Stuart, Juthathip Mongkolsapaya, Jonathan Nguyen-Van-Tam, Matthew Snape, Gavin Screaton, the Com-COV2 study group

Pre-print published in MedRxiv on 10 December 2021

In this report, we present live neutralisation titres against SARS-CoV-2 Omicron variant, compared with neutralisation against Victoria, Beta and Delta variants. Sera from day-28 post second-dose were obtained from participants in the Com-COV2 study who had received a two-dose COVID-19 vaccination schedule with either AstraZeneca (AZD1222) or Pfizer (BNT162b2) vaccines. There was a substantial fall in neutralisation titres in recipients of both AZD1222 and BNT16b2 primary courses, with evidence of some recipients failing to neutralise at all. This will likely lead to increased breakthrough infections in previously infected or double vaccinated individuals, which could drive a further wave of infection, although there is currently no evidence of increased potential to cause severe disease, hospitalisation or death.


Reuters article – Two-dose vaccines induce lower antibodies against Omicron, study finds (Open access)


MedRxiv article – Reduced neutralisation of SARS-COV-2 Omicron-B.1.1.529 variant by post-immunisation serum (Open access)


See more from MedicalBrief archives:


Triple shot of Pfizer vaccination ‘neutralises Omicron variant ‘


Mixing COVID-19 vaccinations gives better immune response — Oxford trial


Boosters significantly strengthen immunity — Cov-Boost trial



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