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Excerpts from The New England Journal of Medicine
India
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New Delhi, December 25, 2020 :
Salient Features :
- Extent to which previously infected people are protected from a second infection is uncertain. This study was conducted to find out whether post-infection immunity exists, how long it lasts, and the effect on prevention of Covid infection.
- A prospective longitudinal cohort study of health care workers was conducted at Oxford University Hospital U.K to assess the relative incidence of subsequent Covid infections in health care workers who were seropositive for SARS-CoV-2 antibodies and as compared to those who were seronegative.
- 11,364(90.6%)seronegative (negative antibody test) and 1179 (9.4% ) seropositive (Positive antibody test) Health Care Workers were followed with two weekly PCR tests for a median period of > 6 month(200 days)
- 223 anti-spike–seronegative (Antibody negative) health care workers had a positive PCR test, whereas 2 anti-spike– seropositive (Antibody positive) health care workers had a positive PCR test (P=0.002). Both these workers were asymptomatic
- The incidence of positive PCR tests was inversely associated with anti-spike antibody titres
- The incidence of PCR-positive results fell with increasing antinucleocapsid antibody titres
According to Dr G C Khilnani , “Second infection (Re-infection) with Covid and value of antibodies inprotection is a burning question. This land mark study published TODAY has clarified several important issues which are disturbing our minds. It is true that all of us are sceptical and worried about the re-infection and wonder whether the vaccine which leads to production antibodies would indeed protect us from infection. Phase I and phase II (and some phase III) trials have revealed that antibodies (both to spike protein and necleocapsid) are formed in response to vaccination.”
This Government funded study done at Oxford University Hospital in UK has convincingly proved that presence anti-spike and anti-nucleocapsid IgG antibodies was associated with a substantially reduced risk of SARS-CoV-2 reinfection in the ensuing 6 months. It also suggests the infection, if occurs in seropositive (those with antibodies in their blood), is trivial (asymptomatic). This study is very encouraging and instils hope of protection. However, it is also clear that the protection is not 100% and the proven duration of protection is 6 months (duration of study). It is to be seen as to how long the antibodies would last (months or years). It is also to be seen whether these antibodies would give protection against new mutated virus (UK) which has shaken the world.
According to Dr G C Khilnani , vaccine is going to give us great protection, however, we will have to continue our practice of life style modification (mask, social distancing and hand hygiene) for long time. While the last pandemic (Spanish Flu) killed estimated 50 million people, the damage due to the current pandemic is reduced with knowledge gathered by studies conducted by scientists all over the world which led to guidelines for prevention and treatment.
Dr Khilnani said, “We should make use of Scientific knowledge to minimise transmission of this disease which has taken away so many lives and changed our life. We hope to get back too normalcy over a period of short time.”
Author : G C Khilnani Chairman, PSRI Institute of Pulmonary, Critical care and Sleep Medicine, PSRI Hospital, New Delhi. Formerly, Professor and Head Dept of Pulmonary Critical care and Sleep Medicine, AIIMS, New Delhi-110029 [email protected]
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