Immunity against COVID19 does not wane with antibodies
Many variants of the SARS2 virus were detected since the virus first appeared. More recently, the Omicron variant of the SARS2 virus has rapidly spread worldwide and became the dominant variant. Recent research has shown that this was mostly due to its ability to evade antibody-mediated immunity from both past infection as well as vaccination.
One unfortunate fact that characterizes the newly developed mRNA vaccines against the SARS2 virus is the relatively quick decline in the level of antibodies against the viral spike protein, between 2-6 months following vaccination.
This raised concerns of insufficient vaccination against future variants in the population.
However, although the Omicron variant spread rapidly worldwide, it did not cause a more severe diseases, especially in vaccinated individuals.
What then, is the reason that despite the relatively low antibody level following vaccination, and the ability of the virus to evade whatever antibodies that are present in the body, that the Omicron variant did not result in severe disease in large numbers worldwide?
Our immune system is comprised of multiple weapons, of which antibodies, made by immune cells called plasma cells, are just one of those weapons. Another weapon is a type of immune cells called immune cytotoxic T cells.
These cytotoxic T cells can identify and directly bind to cells infected with the virus and kill these cells to prevent spread of the viruses to other cells.
Researchers suspected that In light of the persistent protection against the SARS2 virus despite low antibodies levels, Cellular immune responses, particularly by cytotoxic T cell responses, probably contribute to protection against severe SARS-CoV-2 infection.
Two studies now published in the journal ‘Nature’ show that the cellular immunity induced by current vaccines against SARS-CoV-2 is highly conserved to the SARS-CoV-2 Omicron spike protein.
Specifically, individuals who received either the adenoviral or mRNA vaccines against the SARS2 virus demonstrated durable spike-specific immune T cell responses, which reacted similarly to the Beta, Delta and the Omicron variants.
Therefore, current vaccines still show robust protection against severe disease with the SARS-CoV-2 Omicron variant despite the substantially reduced neutralizing antibody responses.
Link to original studies:
https://www.nature.com/articles/s41586-022-04460-3
https://www.nature.com/articles/s41586-022-04465-y
Image credits:
Photo by Artem Podrez: https://www.pexels.com/photo/person-holding-covid-19-vaccine-vial-5878513/
Photo by Kaique Rocha: https://www.pexels.com/photo/people-walking-on-pedestrian-lane-during-daytime-109919/
Photo by Monstera: https://www.pexels.com/photo/interior-of-travel-agency-workplace-7411973/
Photo by Edward Jenner: https://www.pexels.com/photo/coronavirus-scale-model-on-peach-background-4031871/
Special thanks to:
Daniella Biton
Ofir Zvik
