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Immune responses to one dose of COVISHIELD
The February-March 2021 immunogenicity studies carried out by the Sri Jayewardenepura University’s Allergy, Immunology and Cell Biology Unit, Department of Immunology and Molecular Medicine on Sri Lankan healthcare workers who were the first to get the jab with AstraZeneca’s COVISHIELD vaccine have been published in the scientific journal ‘Nature Communications’ on Thursday.
The local research team headed by Prof. Neelika Malavige investigated antibody responses to SARS-CoV-2, neutralizing antibody responses, antibody responses to the variants, along with T cell responses.
They had found the following with regard to the immune responses to a single dose of COVISHIELD:
- 93.4% healthcare workers developed antibodies to a single dose of the vaccine, while 97.1% developed neutralizing antibodies. (Antibodies or immunoglobulins are protective proteins produced by the immune system in response to the presence of the virus.)
- There was no difference in immune responses in younger individuals compared to those >60 years of age.
- The vaccine induced potent T cell responses with 67.1% developing T cell responses.
- However, the antibody responses to the beta SARS-CoV-2 virus variant (the South African variant – B.1.351 or the 501Y.V2) was low.
- The antibodies to Delta (the Indian variant) were not measured, as Delta was not a problem during the time of the study.
Meanwhile, the group is also studying immune responses to other vaccines such as Sputnik V, Moderna and Sinopharm and how the immunity to these different vaccines persists. They are also comparing it with natural infection.
| Delta shows “escape” from vaccine-induced immunity Even though AstraZeneca’s COVISHIELD induced high neutralising antibody responses even after a single dose, a single dose gives less protection against variants such as Delta. Therefore, it is vital to get the second dose with the emergence of Delta, as only both doses would protect a person against such variants, Prof. Neelika Malavige said. She stressed that Delta has been shown to escape vaccine-induced immunity. Therefore, many people who have received both doses of any vaccine can get infected, although infection rates are “very much less” than in those who are unvaccinated. | |