Science

Covid-19: Expert calls for national pandemic prevention programme

Vinson Kurian Thiruvananthapuram | Updated on June 07, 2021

Genomic studies may help evolve early warning system

India should ideally carry out large-scale 'genomic epidemiology' or genomic studies of the 2019-novel coronavirus (2019-nCoV) and its variants, according to Dr Satish Ranjan, Germany-based molecular immunologist and a Covid-19 scientific consultant.

This should be adopted as national pandemic prevention programme and surveillance information policy for characterising new emerging variants to predict outcome on disease severity and its overall short-term and long-term impact on social and economic life.

Dr Ranjan said that this should be followed by studying the new variants in terms of transmissibility, pathogenicity, virulence and immune escape. This is important in the context of getting to know about their exact prevalence and implications as well as for formulating required guidelines and policies.

Lessons to be learnt

Absence of extensive genomic surveillance and lack of assessment of its impact was responsible for precipitating the severe second wave. Lessons need to be learnt from how variant B.1.617 drove the wave from late last year but was not acknowledged until March,2021, Ranjan says.

Also read: Australia’s Victoria logs biggest rise in Covid-19 cases in a week

"It is well understood that variants may emerge and spread silently in future. We need to do the genomic epidemiology to develop an early warning system and prescribe Covid-appropriate behaviour and other measures to avoid the spread of disease."

Making genomic epidemiology a permanent part of pandemic preparedness would improve responses to problematic variants of any infectious disease in future as well, Ranjan told BusinessLine.

Immunity from antibodies

A research article published in the 'Science' journal has said that immunity offered by antibodies can last up to eight months after natural infection but that offered by other components of the immune system can remain for longer.

Immunity from antibodies can be variant-specific and may not provide blanket shield against emerging variants. Virus undergoing mutations in spike protein may escape neutralisation by antibodies as they take on proteins located on the virus surface, especially spike proteins.

Study involving only antibody-mediated immunity may not reflect the efficacy of other components of immunity, especially that of T-cell immunity, which lead to viral clearance independent of antibodies. This immunity can last longer irrespective of fading antibodies and may also work against variants as it can target proteins inside the virus.

Comprehensive immunity study

Comprehensive studies involving the outcome of all components of natural immunity are needed to understand the effectiveness and longevity of naturally acquired immunity post infection, Ranjan pointed out.

A comprehensive immunity study in combination with genomic sequencing data (genomic epidemiology) will throw light on actual immunity against the variants and possibilities of re-infection by other prevailing or emerging variants, Ranjan said.

"It is very important to understand whether re-infections are caused by different variants, in which case, attaining comprehensive herd immunity may remain a distant dream. Attained herd immunity will be only strain specific. Re-infection from emerging variants will still be possible with varying degree of disease severity."

Genomic sequencing data

Genomic sequencing of variants from vaccinated individuals will provide a real-time understanding of effectiveness of vaccine-induced immunity. This will reveal which variants are responsible for infection and re-infection post vaccination and disease severity compared with the non-vaccinated. This data will help thwart many apprehensions about vaccination.

The future of this pandemic will depend heavily on the type of immunity acquired through infection or vaccination and how the virus evolves over a period of time, said Ranjan.

Emerging evidence suggest it is nearly impossible to eradicate this virus which may remain as endemic to a given area/country. "We can hope to deal with it only with proper understanding of evolving strains by adopting a 'genomic epidemiology' study and by doing a comprehensive immunity study," Ranjan said.

Published on June 07, 2021

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