News Release

Vaccine monitoring crucial as SARS-CoV-2 variants continue to evolve

Peer-Reviewed Publication

The Francis Crick Institute

Researchers at the Francis Crick Institute and the National Institute for Health and Care Research Biomedical Research Centre at UCLH have highlighted the importance of continued surveillance of emerging SARS-CoV-2 variants and vaccine performance as the virus continues to evolve.

Published today as a research letter in The Lancet, their study compared the newer monovalent COVID vaccine, which specifically targets the XBB variant of Omicron (as recommended by the World Health Organisation), with older bivalent vaccines containing a mix of an Omicron variant and the original strain of COVID-19, which the UK deployed in Autumn 2023 before turning to monovalent vaccines1

The researchers found that both vaccines generated neutralising antibodies against the most recent strain of Omicron, BA.2.86. However, the new monovalent vaccine generated higher levels of antibodies against a range of other Omicron variants.

The team collected blood and nasal mucosal samples both before and after a fifth dose vaccination from 71 participants of the Legacy study, a research collaboration between the Crick and the NIHR University College London Hospitals Biomedical Research Centre. They compared the antibody levels before and after vaccination.

All 36 participants who received the bivalent vaccine and 17 who received the monovalent vaccine had boosted levels of antibodies against all variants tested, including the newest strain BA.2.86, which caused a wave of infection this winter. But those with the newer monovalent vaccine had 3.5x higher levels of antibodies against the XBB and BQ.1.1 strains after their booster vaccination.

Since the Omicron virus is highly transmissible and the virus replicates in the nose and throat, the researchers tested the levels of antibodies in the participants’ nasal cavity.

They found that the monovalent vaccine increased their ability to produce mucosal antibodies against most of the tested variants, whereas the bivalent vaccine didn’t provide a significant boost.

Neither vaccine increased neutralising antibody levels in the nasal cavity against the newest variant, BA.2.86, suggesting that current vaccines may be less likely to stop transmission or prevent asymptomatic or mild illness, while still protecting against severe disease.

This highlights the importance of careful vaccine updates and continuing to complement a vaccination programme with the development of antibody drugs that work against all variants, as some more vulnerable people don’t respond well to vaccines.

Emma Wall, Senior Clinical Research Fellow at the Crick and Consultant in Infectious Diseases at UCLH, said: “The UK’s strategy to deploy stocks of older vaccines paid off last year, as both vaccines provided equal protection against the newest strain. However, ongoing monitoring is needed, as the virus is continuing to evolve, so vaccine-induced antibodies might not work so well in the future. In the long run, vaccines that are effective against all new variants and can block COVID-19 being transmitted from person to person are needed.”

David LV Bauer, Group Leader of the RNA Virus Replication Laboratory at the Crick, said: “The situation this winter could have been different if the newly emerged BA.2.86 and JN.1 variants were substantially distinct from older Omicron variants, but fortunately this wasn’t the case.

“Most new variants arise quicker than most clinical trials can produce data. But laboratory analysis can provide a detailed picture very quickly. Continued surveillance will help us stay on top of viral evolution.”


For further information, contact: or +44 (0)20 3796 5252

Notes to Editors

Reference: Shawe-Taylor, M and Greenwood, D. et al. (2024). Divergent performance of vaccines in the UK autumn 2023 COVID booster campaign. The Lancet. 10.1016/S0140-6736(24)00316-7.

  1. In Autumn 2023, the UK deployed stocks of ‘bivalent’ vaccines, which encode the Spike protein of the Omicron BA.5 variant that circulated in 2022, and the original 2019 strain of COVID-19, before turning to newer ‘monovalent’ vaccines, which encode the Spike protein of the XBB.1.5 Omicron variant that circulated in early 2023.

The Francis Crick Institute is a biomedical discovery institute dedicated to understanding the fundamental biology underlying health and disease. Its work is helping to understand why disease develops and to translate discoveries into new ways to prevent, diagnose and treat illnesses such as cancer, heart disease, stroke, infections, and neurodegenerative diseases.

An independent organisation, its founding partners are the Medical Research Council (MRC), Cancer Research UK, Wellcome, UCL (University College London), Imperial College London and King’s College London.

The Crick was formed in 2015, and in 2016 it moved into a brand new state-of-the-art building in central London which brings together 1500 scientists and support staff working collaboratively across disciplines, making it the biggest biomedical research facility under a single roof in Europe.

About UCLH

UCLH (University College London Hospitals NHS Foundation Trust) provides first-class acute and specialist services in five hospitals in Central London including the National Hospital for Neurology and Neurosurgery at Queen Square which is the largest hospital of its kind in the UK. UCLH is committed to education and research and forms part of UCLPartners which in March 2009 was officially designated as one of the UK's first academic health science centres by the Department of Health. UCLH works closely with UCL, translating research into treatments for patients. For more information visit We are also on Facebook (UCLHNHS), Twitter (@uclh), Youtube (UCLHvideo) and Instagram (@uclh).

About the NIHR

The National Institute for Health and Care Research (NIHR) is the nation's largest funder of health and care research. The NIHR:

  • Funds, supports and delivers high quality research that benefits the NHS, public health and social care
  • Engages and involves patients, carers and the public in order to improve the reach, quality and impact of research
  • Attracts, trains and supports the best researchers to tackle the complex health and care challenges of the future
  • Invests in world-class infrastructure and a skilled delivery workforce to translate discoveries into improved treatments and services
  • Partners with other public funders, charities and industry to maximise the value of research to patients and the economy

The NIHR was established in 2006 to improve the health and wealth of the nation through research, and is funded by the Department of Health and Social Care. In addition to its national role, the NIHR supports applied health research for the direct and primary benefit of people in low- and middle-income countries, using UK aid from the UK government.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.