CONTEXT : Studies published in the New England Journal of Medicine (NEJM), pointed out that bivalent boosters made to counter both the Omicron strains and the original Covid-19 strain don’t generate significantly greater antibody responses than an additional dose of the original mRNA vaccines.
As per the scientists, this observed ineffectiveness of the bivalent or variant-specific boosters might be due to immune imprinting.
WHAT IS IMMUNE IMPRINTING ?
- As many countries 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 but recent studies has shown that a phenomenon in our bodies, called IMMUNE IMPRINTING might be making these new booster vaccines far less effective than as expected.
- BIVALENT BOOSTERS : The bivalent COVID-19 vaccines or boosters include a duo component of the original virus strain to provide protection against COVID-19 and a component of the omicron variant to provide protection against infection caused by the omicron variant.
- IMMUNE IMPRINTING : It is a tendency of the body to repeat its immune response based on the first variant it encountered either through infection or vaccination, when it comes across a new or slightly different variant of the same pathogen.
- In other words immunological imprinting means your immune memory preferentially sees what it has seen before.
- Initially it was termed as “ORIGINAL ANTIGENIC SIN”, when it was first observed in 1947.
- Over the years scientists have realised that immune imprinting acts as a database for the immune system, helping it to put up a better response to repeated infections.
HOW BOOSTERS ARE INEFFECTIVE ?
- Whenever a vaccinated body encounters a new strain of virus, our immune system should create a new and stronger antibody to kill the variant. But immune imprinting prevents our immune system from creating new and strong antibodies.
- The human body uses the previous memory cells to form new antibodies rather than creating new antibodies known as cross-reactive antibodies.
- Suppose Person 1 was infected with normal COVID and Person 2 was infected with the new variant. Person 1 has taken his vaccine doses but person 2 has not. To counter new variant doctors give vaccine doses to both persons. Booster doses are provided to person 1 and the normal doses are given to person 2 as this is the first time for person 2.
OUTCOME : Immunity built-in Person 2 is high. Because person 1 uses memory cells to counter new variant. On the other hand, person 2 will build new antibodies against variant virus.
HOW TO DEAL WITH IMMUNE IMPRINTING ?
- According to some scientists, “nasal vaccines might be better at preventing infections than the injected vaccines”. As they believe the mucous membranes would create stronger protection despite carrying some imprint of past exposure.
- Researchers are also trying to find if coronavirus vaccine shots on an annual basis could help with the problem of imprinting.
- PAN-SARBECOVIRUS VACCINES : There are considerable efforts directed toward developing new pan-sarbecovirus vaccines that will protect against all COVID-causing variants and maybe even protect against other SARS and related viruses.
B-CELLS AND ANTIBODIES
- As when 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.
- The problem occurs when a different variant of the same 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”.
- Although these cross-reactive antibodies produced by memory B-cells do offer some protection against the new strain, but they are not as effective as the original antibodies ones produced by the B cells when the body first came across the original virus.
OTHER FINDINGS OF RECENT STUDIES
- It was observed in the studies that the bivalent boosters “did not elicit a discernibly superior virus-neutralising peak antibody response as compared with boosting with the original monovalent vaccines” across all coronavirus strains tested.
- The authors of the Columbia University research said that even if the bivalent boosters are as effective as the original ones that doesn’t mean people should not get the bivalent booster.
- The findings of the studies suggested that immune imprinting might be posing a hurdle in the success of the bivalent or variant-specific vaccines.
- Scientists suggest that regardless of the type, coronavirus vaccines are crucial in preventing serious illness.
- Scientists also observed that “there is a need to come up with a vaccine that can overcome imprinting and check the transmission of the virus”.
SOURCE : THE INDIAN EXPRESS
Syllabus : MAINS, GS-3 Science and Technology