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 Table of Contents  
Year : 2022  |  Volume : 12  |  Issue : 2  |  Page : 49-50

COVID Immunity

Department of Pulmonary Medicine, Guwahati Medical College & Hospital, Guwahati, Assam, India

Date of Submission13-Sep-2022
Date of Acceptance13-Sep-2022
Date of Web Publication23-Nov-2022

Correspondence Address:
Prof. (Dr.) Basanta Hazarika
Department of Pulmonary Medicine, Guwahati Medical College & Hospital, Guwahati, Assam
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2278-8239.361831

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How to cite this article:
Hazarika B. COVID Immunity. Assam J Intern Med 2022;12:49-50

How to cite this URL:
Hazarika B. COVID Immunity. Assam J Intern Med [serial online] 2022 [cited 2023 Mar 22];12:49-50. Available from: http://www.ajimedicine.com/text.asp?2022/12/2/49/361831

  Antiviral Immunity Top

There are two types of immune system in our body: the innate and adaptive immune systems. Innate immune responses are the first line of defense against viruses. Adaptive immune responses, the second line of defense against viruses, involve antigen-specific recognition of viral epitopes. Adaptive immunity includes two complementary branches of the immune system: humoral immunity and cellular immunity. Humoral immunity to coronavirus disease-2019 (COVID-19) includes antibodies that bind the COVID-19 spike protein and either neutralize the virus or eliminate it through other effector mechanisms. Cellular immunity to COVID-19 includes virus-specific B cells and T cells, which provide long-term immunologic memory and rapidly expand on re-exposure to antigen. B cells produce antibodies, CD8+ T cells directly eliminate virally infected cells, and CD4+ T cells provide help to support the immune responses.

  Measuring Immune Responses Top

The immune response following infection with a virus can be measured by the detection of virus-specific antibodies such as IgA, IgM, IgG, or total antibodies through immunoassays, as well as by the detection of sensitized memory B cells and/or CD4+ and CD8+ T cells. The most commonly measured immune response is the presence of antibodies in serum. Serologic assays to detect the antibody response are usually based on enzyme immunoassays and testing has limited use in clinical management because it does not capture active infection; it can be very useful in determining the extent of infection or estimating attack rates in given populations. The most frequently used assays for detection of antibodies to COVID-19 are enzyme-linked immunosorbent tests, chemiluminescent tests, and lateral flow rapid diagnostic tests (RDTs).

  COVID-19 Immune Responses to Natural Infection Top

After infection with COVID-19, 90%–99% of infected individuals develop neutralizing antibodies within 2–4 weeks after infection.[1],[2] A small proportion of individuals do not develop neutralizing antibodies after COVID-19 infection for reasons that are unclear.[2] Individuals with mild or asymptomatic infection tend to have lower antibody levels than those with severe disease, and some studies have suggested that in some individuals, waning of antibody levels occurs within several months after infection.[3] How much cellular versus humoral immunity contributes to protection after natural infection is not fully understood. Studies point at neutralizing antibodies as a key element of immunoprotection, with cellular immunity likely to provide additional longer-term protection, especially against severe disease and death.[4] How long overall protection may last remains unclear, and this may differ depending on the disease severity. Reinfection with COVID-19 after recovery from COVID-19 infection can occur. In different studies, it was estimated that infection with COVID-19 provided 80%–90% protection from reinfection up to 7 months, and up to 94% protection against symptomatic disease.[5]

  COVID-19 Immunity with Vaccination Top

Vaccination induces an immune response in a safe way and significantly reduces the chances of developing COVID-19. Even if a person had COVID-19, vaccination will safely boost whatever immunity a person had from previous infection. The U.S. Centers for Disease Control and Prevention (CDC) released a report on October 29, 2021, getting vaccinated for the coronavirus significantly enhances immune protection and further reduces the risk of reinfection. A study published in August 2021 indicates that if a person had COVID-19 before and is not vaccinated, the person’s risk of getting re-infected is more than two times higher than of those who got vaccinated after having COVID-19.[6]

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Conflicts of interest

There are no conflicts of interest.

  References Top

Wajnberg A, Mansour M, Leven E, Bouvier NM, Patel G, Firpo-Betancourt A, et al. Humoral response and PCR positivity in patients with COVID-19 in the New York city region, USA: An observational study. Lancet Microbe 2020;1:e283-9.  Back to cited text no. 1
Arkhipova-Jenkins I, Helfand M, Armstrong C, Gean E, Anderson J, Paynter RA, et al. Antibody response after SARS-CoV-2 infection and implications for immunity: A rapid living review. Ann Intern Med 2021;174:811-21.  Back to cited text no. 2
Huang C, Huang L, Wang Y, Li X, Ren L, Gu X, et al. 6-month consequences of COVID-19 in patients discharged from hospital: A cohort study. Lancet 2021;397:220-32.  Back to cited text no. 3
Sekine T, Perez-Potti A, Rivera-Ballesteros O, Strålin K, Gorin JB, Olsson A, et al; Karolinska COVID-19 Study Group. Robust T-cell immunity in convalescent individuals with asymptomatic or mild COVID-19. Cell 2020;183:158-68.e14.  Back to cited text no. 4
Lumley SF, O’Donnell D, Stoesser NE, Matthews PC, Howarth A, Hatch SB, et al; Oxford University Hospitals Staff Testing Group. Antibody status and incidence of SARS-cov-2 infection in health care workers. N Engl J Med 2021;384:533-40.  Back to cited text no. 5
MMWR Morb Mortal Wkly Rep 2021;70:1081-3.  Back to cited text no. 6


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