How have SARS-CoV-2 variants of concern impacted national case fatality rates?

Since November 2020, there has been a rapid emergence and spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VoCs). These VoCs are often associated with enhanced transmissibility and virulence as compared to the ancestral strain of SARS-CoV-2.

Study: The influence of SARS-CoV-2 variants of concern on national case fatality rates. Image Credit: Mediantone / Shutterstock.com

Recently, the SARS-CoV-2 Delta variant has become the dominant circulating strain in several countries, including India and the United States. In addition to the Delta variant, there have also been increasing reports on the Lambda variant, which has also been associated with increased resistance against vaccines as it spreads through much of South America.

As of August 23, 2021, SARS-CoV-2 has infected over 212 million and caused the deaths of almost 4.5 million people worldwide. A new study available on the pre-print server medRxiv* aims to analyze the degree to which the new VoCs cause fluctuations in daily case fatality rates (CFR) across several countries, and whether these variants increase the vulnerability of patients with certain comorbidities to COVID-19.

About the study

To determine the effect of SARS-CoV-2 VoCs, the researchers utilized a credible proxy for daily case fatality rates (pCFR) that is sensitive to the spread of the variants throughout a given country.

To determine any changes in the susceptibility of the patient population to co-factors, the researchers conducted linear correlation studies. In these studies, the data was based on national epidemiological statistics that were reported to the relevant national and international authorities.

Study findings

The pCFR provides a useful metric that helps to track the spread of the SARS-CoV-2 VoCs, along with monitoring the country’s vaccination implementation program. In the United Kingdom, a rise in the COVID-19 fatality rate was observed following the emergence of the Alpha variant.

However, a sharp decline in this nation’s fatality rate occurred following the implementation of an ambitious vaccination program. This low fatality rate was found to persist despite the spread of the Delta variant across the United Kingdom.

With respect to the United States and Germany, an increase in the daily pCFR was observed following the spread of the Delta variant. This suggests that the Delta variant was much more virulent than the ancestral strain of SARS-CoV-2.

The study concluded that the increase in virulence of the SARS-CoV-2 VoCs might be due to the presence of certain comorbidities in persons that leads to depressed functioning of the immune system, which can increase the severity of COVID-19 infection in those individuals.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Suchandrima Bhowmik

Suchandrima has a Bachelor of Science (B.Sc.) degree in Microbiology and a Master of Science (M.Sc.) degree in Microbiology from the University of Calcutta, India. The study of health and diseases was always very important to her. In addition to Microbiology, she also gained extensive knowledge in Biochemistry, Immunology, Medical Microbiology, Metabolism, and Biotechnology as part of her master's degree.