Immune imprinting

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    In Context

    • Recently, studies have found ‘immune imprinting’ might be making bivalent boosters less effective.

    More about the news

    • About:
      • Countries like the UK and the US have rolled out variant-specific or bivalent boosters, in the hope that they would provide better protection against the coronavirus infection in comparison to the original vaccine. 
        • However, studies have shown that a phenomenon in our bodies, called immune imprinting, might be making these new boosters far less effective than expected.
    • Bivalent boosters:
      • Bivalent boosters are made to counter both the Omicron strains and the original Covid-19 strain.

    More about immune imprinting

    • Meaning:
      • Immune imprinting is a tendency of the body to repeat its immune response based on the first variant it encountered through infection or vaccination — when it comes across a newer or slightly different variant of the same pathogen.
    • Origin:
      • The phenomenon was first observed in 1947, when scientists noted that 
        • “People who had previously had flu, and were then vaccinated against the current circulating strain, produced antibodies against the first strain they had encountered”, according to a report published in the journal Nature. 
      • At the time, it was termed the ‘original antigenic sin’ but today, it’s commonly known as imprinting.
    • How does it work?
      • Over the years, scientists have realised that imprinting acts as a database for the immune system
        • It helps put up a better response to repeat infections
      • After our body is exposed to a virus for the first time, it produces memory B cells that circulate in the bloodstream and quickly produce antibodies whenever the same strain of the virus infects again.
    • Issue:
      • The problem occurs when a similar, not identical, variant of the virus is encountered by the body. 
        • In such cases, the immune system, rather than generating new B cells, activates memory B cells, which in turn produce antibodies that bind to features found in both the old and new strains, known as cross-reactive antibodies.
      • Although these cross-reactive antibodies do offer some protection against the new strain, they aren’t as effective as the ones produced by the B cells when the body first came across the original virus.
    • Ways to deal with immune imprinting
      • Nasal vaccines: Some scientists have said nasal vaccines might be better at preventing infections than injected ones. 
        • They believe the mucous membranes would create stronger protection, despite carrying some imprint of past exposure.
      • Spacing vaccine shots: Researchers are also trying to find if spacing out coronavirus vaccine shots on an annual basis, could help with the problem of imprinting.

    Pan-sarbecovirus vaccines: There’s also considerable effort directed toward developing what’s called pan-sarbecovirus vaccines that will protect against all COVID-causing variants and maybe even protect against other SARS and related viruses.