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expert reaction to two papers looking at T cells (after COVID-19 vaccination or infection) and Omicron

Two studies, published in the journal Nature, have looked at T cells (after COVID-19 vaccination or infection) and Omicron.


Prof Eleanor Riley, Professor of Immunology and Infectious Disease, University of Edinburgh, said:

“The findings from these studies are not surprising but they are very welcome and reassuring.

“Unlike neutralising antibodies that must bind very tightly to the particular small region of the spike protein that attaches to the host cell, T cells can function effectively whichever region of the virus they recognise.  Our T cell responses are  highly diverse – both within an individual and between different people – and much less affected by a small number of mutations scattered across the virus.

“The finding that T cells of people who have been vaccinated against, or infected with, SARS-CoV-2 can recognise all the major variants of the virus that have emerged so far is thus pretty much as predicted and likely explains why the vaccines continue to be so effective against severe disease, whichever variant is circulating.  Whilst, in theory, variants that significantly evade T cell responses could arise, the diversity and complexity of T cell responses makes this highly unlikely.

“These studies also indicate that T cell responses are much more durable than neutralising antibodies, showing no significant decline over 8 months of follow up.  This is also very good news in terms of the ability of Covid-19 vaccines to confer long term protection.”


Prof Lawrence Young, Virologist and Professor of Molecular Oncology, Warwick Medical School, University of Warwick, said:

“These are very important and encouraging papers in terms of the ability of vaccine-induced immunity to protect from severe outcomes caused by infection with SARS-CoV-2 variants.  Much attention has focussed on the antibody response to vaccination and the ability of these antibodies to block virus infection.  However, a major component of the antiviral  immune response is mediated by T cells and these have been relatively neglected in studying vaccine-induced immune protection.  T cells can recognise and destroy virus-infected cells as well as promote the production of antibodies.  T cell responses induced by vaccination can provide long-term protection against the severe consequences of infection.

“These two studies show that while the protective antibody response induced by vaccination is not sufficient to prevent infection with the omicron variant, vaccination with either mRNA or adenovirus-based vaccines stimulate robust and durable T cell responses to the omicron variant.  The studies showed consistent T cell responses across different variants and demonstrated that natural infection also induced cross-reactive T cell responses.  Current vaccines are based on the spike protein from the original Wuhan strain of the virus and these new studies confirm high levels of cross-reactivity of T cell responses with the omicron and other variants.  This provides a possible explanation for the lower risk of hospitalisation and severe disease associated with omicron infection in vaccinated individuals as well as those infected with previous variants.

“These studies bode well for the ability of vaccine-induced immunity to protect against severe disease induced by future virus variants.  One issue not fully addressed by these studies is the degree to which these T cell responses wane over time although one of the studies measured responses 8 months after vaccination.”


Prof Penny Ward, Independent Pharmaceutical Physician, and Visiting Professor in Pharmaceutical Medicine at King’s College London, said:

“Two complimentary studies today exploring cellular immune responses to various SARS COV2 variants, particularly omicron, following vaccination/natural infection support the conclusion that, in contrast to antibody responses which are specific to the spike antigen coded for by the vaccine administered, cellular immune response is broader with T cell responses demonstrated against all viral variants tested.  While both papers explored cell responses assessed in blood taken within 1 month of vaccination/convalescence, Liu et al also evaluated retention of cellular response at month 8 post vaccination/convalescence demonstrating that responses are retained while neutralising antibody titre is significantly reduced.  While antibody is considered to be the more important in offering protection from infection, cellular immune response is considered to be important for control of disease severity.

“These data offer at least one explanation for the observed retained protection against severe disease following reinfection in vaccinated patients during the recent omicron wave, and offer at least some reassurance that these broad responses may also blunt disease severity should, as expected, further variants emerge.  Yet another reason to be vaccinated, particularly if working in a high risk environment – health and social care workers take note!”


‘T cell responses to SARS-CoV-2 spike cross-recognize Omicron’ by Roanne Keeton et al. was published in Nature on Monday 31 January 2022.

DOI: 10.1038/s41586-022-04460-3

‘Vaccines Elicit Highly Conserved Cellular Immunity to SARS-CoV-2 Omicron’ by Jinyan Liu et al. was published in Nature on Monday 31 January 2022.

DOI: 10.1038/s41586-022-04460-3


All our previous output on this subject can be seen at this weblink:



Declared interests

Prof Eleanor Riley: “No COIs to declare.”

Prof Penny Ward: “I am semi-retired, but I am owner/Director of PWG Consulting (Biopharma) Ltd a consulting firm advising companies on drug and device development. Between December 2016 and July 2019 I served as Chief Medical Officer of Virion Biotherapeutics Ltd, a company developing antiviral treatments for respiratory viral diseases. Previous employee of Roche, makers of tocilizumab (anti IL6 antibody) and CMO of Novimmune, makers of empalumab (anti IFN gamma antibody).”

None others received.

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