January 3, 2022

Q&A #09: Do cross-reactive T cells explain mild course of Omicron infection?


Do cross-reactive T cells explain mild course of Omicron infection as suggested by


Note that this paper correctly states that “well-preserved T cell immunity to Omicron is likely to contribute to protection from severe COVID-19”. However, the data shown do not support the statement of these authors that “cross-reactive T cell responses acquired through vaccination or infection may contribute to these apparent milder outcomes for Omicron”. There is quite a difference between protection against symptomatic infection and protection from severe disease!

It will probably take some more time before scientists understand that cross-reactive CoV-specific T cells cannot explain the asymptomatic/ mild course of Omicron infection. CoV-specific T MEMORY cells do not provide sterilizing immunity and therefore cannot prevent or abrogate viral transmission. Of course, cytokines secreted by cross-reactive CoV-specific T cells could enhance recovery from disease and avoid a more severe course of C-19 illness. This is simply due to a T cell-mediated ‘adjuvant’ effect.

If in vivo priming of previously CoV-primed cross-reactive memory T cells were responsible for Omicron’s mild course of C-19 disease, one wonders why cross-reactive T memory cells were not already our bodies’ best shot at attenuating disease caused by the Delta variant. And how stupid would (vulnerable) people be to refresh their Flu shot on a yearly basis if cross-reactive T cells would be cross-protective against disease, or even infection. Some pretend, indeed, that vaccine-induced T cell immunity enables the immune system to limit the spread of the virus due to cross-reactivity of CoV-specific T memory cells! If this were to apply, we would expect a similar mechanism to occur in case of Flu vaccines, thereby making yearly vaccination with updated Flu shots completely redundant!

I can only insist that people read the rationale for the statements made above as explained in my recent contribution on this topic:

And there is more: Fighting a viral pandemic with vaccines that only mitigate symptoms is likely to promote immune escape, regardless the immune mechanisms and the underlying effectors that are responsible for this mitigation...

Support our work
Subscribe to our Substack Newsletter

Geert Vanden Bossche received his DVM from the University of Ghent, Belgium, and his PhD degree in Virology from the University of Hohenheim, Germany. He held adjunct faculty appointments at universities in Belgium and Germany. After his career in Academia, Geert joined several vaccine companies (GSK Biologicals, Novartis Vaccines, Solvay Biologicals) to serve various roles in vaccine R&D as well as in late vaccine development.

Geert then moved on to join the Bill & Melinda Gates Foundation’s Global Health Discovery team in Seattle (USA) as Senior Program Officer; he then worked with the Global Alliance for Vaccines and Immunization (GAVI) in Geneva as Senior Ebola Program Manager. At GAVI he tracked efforts to develop an Ebola vaccine. He also represented GAVI in fora with other partners, including WHO, to review progress on the fight against Ebola and to build plans for global pandemic preparedness.

Back in 2015, Geert scrutinized and questioned the safety of the Ebola vaccine that was used in ring vaccination trials conducted by WHO in Guinea. His critical scientific analysis and report on the data published by WHO in the Lancet in 2015 was sent to all international health and regulatory authorities involved in the Ebola vaccination program. After working for GAVI, Geert joined the German Center for Infection Research in Cologne as Head of the Vaccine Development Office. He is at present primarily serving as a Biotech / Vaccine consultant while also conducting his own research on Natural Killer cell-based vaccines.


Recent Posts
July 4, 2024

Like SARS-CoV-2, I'm ready for a major change…

July 3, 2024

This is how I feel

July 3, 2024

Sententia mox dicetur

Voices for Science and solidarity, © 2023