HYBRID IMMUNITY

1. Context 

2. About hybrid immunity

• It is gained from a previous infection plus vaccines either the primary doses or both primary and booster doses.
• The study said hybrid immunity offers a "higher magnitude and durability" of protection compared to infection alone, emphasising the need for vaccination.
• However, with the faster-spreading omicron variants leading to more infections and consequently more people developing this hybrid immunity, the study suggested that booster doses may be delayed.
• We already know that hybrid immunity provides the best protection against infection after vaccination acts like a booster.
• Getting a natural infection best after vaccination so that the risk of death is lower provides better protection than vaccines alone because it prepares the body against the entire virus, rather than say just the spike protein.

3. The study findings

• Protection against severe disease and hospitalisations from a Sars-CoV-2 infection alone was found to be 82. 5 per cent at three months after the last shot or infection.
• This protection stood at 74. 6 per cent at 12 months and 71. 6 per cent at three months and dropped to 24. 7 per cent at 12 months and 15. 5 per cent at 15 months.
• In comparison, hybrid immunity with just the primary vaccine doses was found to be 96 per cent at three months and 97. 4 per cent at 12 months.
• The same can offer 69 per cent protection against reinfection at three months, dropping to 41. 8 per cent at 12 months.
• The effectiveness of hybrid immunity gained from infection coupled with the primary as well as a booster dose stood at 97.2 per cent at three months and 95. 3 per cent at six months.
• The same immunity was found to be 68.6 per cent effective at three months and 46. 5 per cent at six months.

4. The implication of the findings

• These results provide information that can be used to tailor guidance on the number and timing of SARS-CoV-2 vaccinations.
• In regions with high Sars-CoV-2 Seroprevalence, the primary vaccination focused mainly on those at the highest risk of severe diseases such as the old or co-morbid can offer high protection against severe disease and hospitalisation for at least one year.
• As per the World Health Organisation, the global seroprevalence of the presence of antibodies against Sars-CoV-2 whether because of infection or vaccination stood at 67 per cent as of October 2021.
• Two-thirds of Indians had these antibodies as early as June-July 2021 after the delta variant wave earlier that year.

For Prelims & Mains