Past Covid Infection Provided Substantial Protection Against Reinfection: Lancet Study

Washington: For people previously infected with COVID-19, their risk of hospitalisation or death is 88 per cent lower for at least 10 months compared to those who had not been previously infected, according to a study published in The Lancet journal. The analysis also suggests that the level and duration of protection against reinfection, symptomatic disease and severe illness is at least on a par with that provided by two doses of the mRNA vaccines (Moderna, Pfizer-BioNtech) for ancestral, Alpha, Delta and Omicron BA.1 variants. The study did not include data on infection from Omicron XBB and its sublineages.

Vaccination is the safest way to acquire immunity, whereas acquiring natural immunity must be weighed against the risks of severe illness and death associated with the initial infection, said lead author Stephen Lim from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington, US.

Study co-author Caroline Stein from IHME explained that vaccines continue to be important for everyone in order to protect high-risk populations such as those who are over 60 years of age and those with comorbidities.

This also includes populations that have not previously been infected and unvaccinated groups, as well as those who were infected or received their last vaccine dose more than six months ago, Stein said.

Decision makers should take both natural immunity and vaccination status into consideration to obtain a full picture of an individual’s immunity profile, the researcher added.

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The team conducted a review and meta-analysis of all previous studies that compared the reduction in risk of COVID-19 among non-vaccinated individuals against a SARS-CoV-2 reinfection to non-vaccinated individuals without a previous infection up to September 2022.
It included 65 studies from 19 countries and evaluates the effectiveness of past infection by outcome (infection, symptomatic disease, and severe disease), variant, and time since infection.
Studies examining natural immunity in combination with vaccination i.e., hybrid immunity were excluded from the analyses.
Analysis of data from 21 studies reporting on time since infection from a pre-Omicron variant estimated that protection against reinfection from a pre-Omicron variant was about 85 per cent at one month — and this fell to about 79 per cent at 10 months, the researchers said.

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Protection from a pre-Omicron variant infection against reinfection from the Omicron BA.1 variant was lower (74 per cent at one month) and declined more rapidly to 36 per cent at around 10 months, they said.
Analysis of five studies reporting on severe disease (hospitalisation and death) found that protection remained universally high for 10 months: 90 per cent for ancestral, Alpha, and Delta, and 88 per cent for Omicron BA.1.
Six studies evaluating protection against Omicron sub-lineages specifically (BA.2 and BA.4/BA.5) suggested significantly reduced protection when the prior infection was pre-Omicron variant.
However, when the past infection was Omicron, protection was maintained at a higher level, according to the researchers.

The weaker cross-variant immunity with the Omicron variant and its sub-lineages reflects the mutations they have that make them escape built-up immunity more easily than other variants, said IHME co-author Hasan Nassereldine.

The limited data we have on natural immunity protection from the Omicron variant and its sub-lineages underscores the importance of continued assessment, particularly since they are estimated to have infected 46 per cent of the global population between November 2021 and June 2022, Nassereldine added.

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(This story has not been edited by NDTV staff and is published from a syndicated feed.)

NDTV – Dettol have been working towards a clean and healthy India since 2014 via the Banega Swachh India initiative, which is helmed by Campaign Ambassador Amitabh Bachchan. The campaign aims to highlight the inter-dependency of humans and the environment, and of humans on one another with the focus on One Health, One Planet, One Future – Leaving No One Behind. It stresses on the need to take care of, and consider, everyone’s health in India – especially vulnerable communities – the LGBTQ population, indigenous people, India’s different tribes, ethnic and linguistic minorities, people with disabilities, migrants, geographically remote populations, gender and sexual minorities. In wake of the current COVID-19 pandemic, the need for WASH (Water, Sanitation and Hygiene) is reaffirmed as handwashing is one of the ways to prevent Coronavirus infection and other diseases. The campaign will continue to raise awareness on the same along with focussing on the importance of nutrition and healthcare for women and children, fight malnutrition, mental wellbeing, self care, science and health, adolescent health & gender awareness. Along with the health of people, the campaign has realised the need to also take care of the health of the eco-system. Our environment is fragile due to human activity, which is not only over-exploiting available resources, but also generating immense pollution as a result of using and extracting those resources. The imbalance has also led to immense biodiversity loss that has caused one of the biggest threats to human survival – climate change. It has now been described as a “code red for humanity.” The campaign will continue to cover issues like air pollution, waste management, plastic ban, manual scavenging and sanitation workers and menstrual hygiene. Banega Swasth India will also be taking forward the dream of Swasth Bharat, the campaign feels that only a Swachh or clean India where toilets are used and open defecation free (ODF) status achieved as part of the Swachh Bharat Abhiyan launched by Prime Minister Narendra Modi in 2014, can eradicate diseases like diahorrea and the country can become a Swasth or healthy India.