What is Hybrid Immunity?

Context

According to a meta-analysis published in “Lancet Infectious Diseases”, Hybrid immunity — from a previous infection coupled with vaccination — offers a “higher magnitude and durability” of protection against severe Covid than an infection alone.

Probable Question

What is Hybrid Immunity?  How does hybrid immunity provide better protection against severe Covid than an infection alone? (150 words, 10 marks)

Highlights of the study

• The study is based on an analysis of 11 other studies on the protective effectiveness of previous SARS-CoV-2 (Covid) infection and 15 studies on the protective effectiveness of hybrid immunity.
• A hybrid immunity offers a “higher magnitude and durability” of protection as compared to infection alone, emphasizing the need for vaccination.
• Hybrid immunity, coupled with primary vaccine doses, was effective in preventing severe disease and hospital admission in 97.4 percent of participants upto 12 months.
  • The effectiveness of only hybrid immunity against reinfection stood at 41.8 percent at 12 months. 
  • And, the effectiveness of only previous infection against severe disease and hospital admission was 74.6 percent at 12 months.
  • After 12 months, protection against reinfection for all forms of immunity dipped to 24.7 per cent.
• The effectiveness of hybrid immunity gained from infection coupled with the primary as well as a booster dose stood at 97.2% at three months and 95.3% at six months.
  • The same immunity was found to be 68.6% effective at three months and 46.5% at six months.
• Hybrid immunity in combination with the first booster vaccination conferred a significant gain in protection compared to first booster vaccination alone at 90 days.
• The study provides information that can be used to tailor guidance on the number and timing of SARS-CoV-2 vaccinations.

Recommendations of the study

• In places with high prevalence of infection and low resources, the focus should be on administering primary doses to people who are at the highest risk of developing severe disease. This, it says, will offer a high level of protection against severe disease for at least one year in people who have had the infection.
  • India has administered two primary doses of vaccine to at least 90 percent of people above the age of 12 years across the country.
• Rolling out booster drives whenever an increase in number of infections is expected. 
• A six-month delay in booster dose “might be justified” in individuals with a known history of previous infection and full primary vaccination.

What is Hybrid Immunity?

• Hybrid immunity is gained from a previous infection plus vaccines – either the primary doses or both primary and booster doses. 
• Hybrid immunity provides better protection than vaccines alone because it prepares the body against the entire virus, rather than just the spike protein.

What are memory B cells?

• A memory B cell is a type of B-lymphocyte that forms part of the adaptive immune system.
  • B lymphocytes are the cells of the immune system that are responsible for producing antibodies that invade pathogens like viruses.
  • They form memory cells that get triggered on subsequent infection or vaccination from the same pathogen for faster antibody production.

News Source: Indian Express

https://indianexpress.com/article/explained/explained-health/hybrid-immunity-most-effective-against-severe-covid-study-8392858/

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