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Covid-19 Impacts the Immune System

Covid-19 Damages and Dysregulates the Immune System

  • Covid causes T-cell exhaustion, meaning the immune system is less able to fight off pathogens (Loretelli et al., 2021 doi: 10.1172/jci.insight.146701)


  • Previous infection with earlier Covid-19 strains can lead to impaired immune responses to Omicron (a variant of Covid-19) (Reynolds et al., 2022 doi: 10.1126/science.abq1841)


  • Covid infects and kills T-lymphocytes (key cells of the immune system), causing low T-lymphocyte counts. 1(Guan et al., 2020 doi: 10.1056/NEJMoa2002032), 2(Shen et al., 2022 doi: 10.1038/s41392-022-00919-x)


  • Long Covid patients show reactivation of latent Epstein-Barr (a virus that can cause MS) and Varicella Zoster (virus that can cause shingles and Ramsey Hunt syndrome) viruses (Klein et al., 2022 *preprint doi: 10.1101/2022.08.09.22278592)


  • 2.8% of Long Covid patients reported Varicella Zoster Virus reactivation, leading to shingles, following Covid infection. Primary risk factors for VZV reactivation are age and immunodeficiency. (Davis et al., 2021 doi: 10.1016/j.eclinm.2021.101019)

  • Covid infection causes immunodefiency in recovered patients by downregulating a specific protein on B Cells (a type of immune cell). (Jing et al., 2021 doi: 10.1038/s41392-021-00749-3)


  • Increases in proteins that promote blood clotting and persistent endothelial cell (blood vessel lining) activation is seen in Long Covid, caused by immune dysfunction (Fogarty et al., 2022, doi: 10.1111/jth.15830)


  • T cell perturbations, similar to those seen in chronic HIV infection, persist for at least 6 months following Covid hospitalisation. (Govender et al., 2022 doi: 10.3389/fimmu.2022.931039)


  • Covid supresses host functional adaptive and innate immunity, causing morbidity and mortality. (Remy et al., 2020, doi: 10.1172/jci.insight.140329)


  • T cell apoptosis (cell death) leads to immunodeficiency in severe Covid infections through a mechanism similar to HIV. (André et al., 2022, doi: 10.1038/s41418-022-00936-x)


  • Persistent T cell abnormalities seen in Long Covid patients more than 3 months after initial infection. The changes seen were not correlated with ongoing subjective ill-health, fatigue and reduced exercise tolerance but were more marked with age. (Townsend et al., 2021, doi: 10.3389/fimmu.2021.676932)


  • Immunological dysfunction persists for at least 8 months following initial mild-to-moderate SARS-CoV-2 infection. (Phetsouphanh et al., 2022, doi: 10.1038/s41590-021-01113-x)


  • Covid patients show long-lasting depletion and functional impairment of dendritic cells and monocytes (immune cells) which may have consequences for susceptibility to secondary infections. (Winheim et al., 2021, doi: 10.1371/journal.ppat.1009742)


  • Long-term perturbation of the peripheral immune system seen months after SARS-CoV-2 infection. (Ryan et al., 2022 doi: 10.1186/s12916-021-02228-6)


  • Omicron subvariants BA.4 and BA.5 show enhanced innate immune suppression (ability to suppress host immune response) compared to earlier variants. (Reuschl et al., 2022 *preprint, doi: 10.1101/2022.07.12.499603)

Covid-19 Causes the Body to Attack Itself (Autoimmunity)

  • Covid causes production of autoantibodies which target the immune system, vascular cells, coagulation factors and platelets, connective tissue, and organ systems, including lung, the central nervous system compartment, skin, gastrointestinal tract and other tissues. (Wang et al., 2021 doi: 10.1038/s41586-021-03631-y)

  • Asymptomatic Covid infection can lead to severe Ulcerative Colitis (an inflammatory bowel disease). (Mora et al., 2022 doi: 10.7759/cureus.25783)

  • Mild Covid infection can produce significant levels of autoantibodies for 7+ months.(Bhadelia et al., 2021 *preprint doi: 10.1101/2021.01.21.21249176)


  • Covid infection precedes new appearance of autoimmune and inflammatory diseases. (Galleoti and Bayry, 2020 doi: 10.1038/s41584-020-0448-7)


  • Covid infection linked to development of vasculitis, arthritis, lupus and sarcoidosis.(Gracia-Ramos et al., 2021 doi: 10.3390/cells10123592)


  • Autoantibodies linked to Lupus, Rheumatoid Arthritis, Guillain-Barré syndrome, immune thrombocytopaenia and autoimmune haemolytic anaemia found in patients following Covid infection. (Moody et al., 2021 doi: 10.3390/ijms22168965)


  • In a group of non-hospitalised healthcare workers with Covid, 54% tested positive for autoantibodies- these targeted skin, smooth muscle, neutrophils (a type of white blood cell of the immune system) and gastric parietal cells (cells in the gut). (Richter et al., 2021 doi: 10.1111/cei.13623)


  • Growing evidence that infection with Covid is associated with the development of autoimmunity from organ-specific to systemic autoimmune and inflammatory conditions. (Gracia-Ramos et al., 2021, doi: 10.3390/cells10123592)


  • Genetically predisposed patients at higher risk of developing celiac disease following Covid infection, as infection causes epithelial damage in the intestines, leading to barrier breakdown. (Trovato et al., 2021, doi: 10.1111/ijcp.14452)


  • New-onset inflammatory bowel disease cases 1-4 months after Covid infection showing Covid may be able to trigger IBD in the same way as acute viral gastroenteritis. (Tursi et al., 2022, doi: 10.1097/MEG.0000000000002379)


  • Covid produces a protein with identical sequences to a liver cell protein, potentially explaining the epidemic of hepatitis seen in children by epitope mimicry causing autoimmune T cell response. (Wang and Liu, 2022, *preprint, doi: 10.1101/2022.05.16.49192)


  • Cases of inflammatory arthritis seen following recovery from Covid infection in patients aged 25-65. (Mukarram et al., 2021, doi: 10.1155/2021/6610340)

Covid-19 Can Lead to Development of New Allergies

• Mast cell activation syndrome (MCAS) may be triggered by Covid infection, resulting in new allergies and risk of anaphylaxis.

(Afrin et al., 2020 doi: 0.1016/j.ijid.2020.09.016)

• Mast cell (cells involved in allergies) activation symptoms are increased in Long Covid

(Weinstock et al., 2021 doi: 10.1016/j.ijid.2021.09.043)

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