One dose enough for those infected with Covid

One dose enough for those infected with Covid

Subject : Science & tech

Context : Single-dose of Covishield vaccine elicits a stronger immunity in individuals recovered from SARS-CoV-2 infection compared with those having no prior exposure, indicated a study published in the International Journal of Infectious Diseases.

Concept :

• All the seropositive or seronegative participants developed neutralizing antibodies by day 28 after the first dose of Covishield.
• The previously infected group mounted greater antibody response to a single dose of Covishield vaccine compared with the no prior exposure group.
• These results suggest protective immune memory in previously exposed individuals after a single dose of vaccine.
• Such individuals could mount memory recall response on a subsequent encounter with antigen as they have developed adaptive immune memory.

Immunological memory 

• Immunological memory is the ability of the immune system to respond more rapidly and effectively to pathogens that have been encountered previously, and reflects the preexistence of a clonally expanded population of antigen-specific lymphocytes.
• Memory responses, which are called secondary, tertiary, and so on, depending on the number of exposures to antigen, also differ qualitatively from primary responses.
• This is particularly clear in the case of the antibody response, where the characteristics of antibodies produced in secondary and subsequent responses are distinct from those produced in the primary response to the same antigen.
• Memory T-cell responses have been harder to study, but can also be distinguished from the responses of naive or effector T cells.
• The principal focus of this section will be the altered character of memory responses, although we will also discuss emerging explanations of how immunological memory persists after exposure to antigen.
• A long-standing debate about whether specific memory is maintained by distinct populations of long-lived memory cells that can persist without residual antigen, or by lymphocytes that are under perpetual stimulation by residual antigen, appears to have been settled in favor of the former hypothesis.