Immune imprinting

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.