The severe acute respiratory syndrome coronavirus disease (COVID-19), which is the pathogen responsible for the coronavirus disease (COVID-19), continues to spread globally. Over 221 million have been infected since December 2020, with over 4.5 million succumbing to this disease.
sTheir study, which was published in The Lancet Infectious Diseases, is the largest one to date, as it analyzed over 40,000 COVID-19 cases. The results of the current suggest that outbreaks of the Delta variant in unvaccinated populations might cause a more significant burden on health care systems than the Alpha variant.
Study: Hospital admission and emergency care attendance risk for SARS-CoV-2 delta (B.1.617.2) compared with alpha (B.1.1.7) variants of concern: a cohort study. Image Credit: Alexandros Michailidis / Shutterstock.com
The threat of the Delta variant
As SARS-CoV-2 evolves and novel variants emerge globally, sustained monitoring and rapid assessment of genetic changes are needed for public health officials to respond immediately to new outbreaks. Moreover, it is essential to monitor the spread of these variants in order to impose proper infection control measures and mitigation strategies.
The B.1.1.7 variant, which is otherwise known as the Alpha variant, was initially detected in England in November 2020 and has been associated with increased transmissibility as compared to previous variants. However, the B.1.617 or Delta variant, which was first reported in India in December 2020, quickly became the dominant circulating variant.
India has seen a rapid increase in confirmed cases and test positivity, with the latter reaching 30% by the end of April 2021. By March 2021, the Delta variant reached England and has accounted for over 50%of SARS-CoV-2 sequence isolates as of May 25, 2021. Scientists have therefore estimated that the Delta variant could be up to 50% more transmissible than the Alpha variant.
The Delta variant is now the most common lineage in several higher- and lower-income countries across the globe. In England, for example, the Delta variant currently accounts for more than 99% of new cases.
Despite vaccination rollouts, the number of cases has steadily increased in India and other countries. For instance, the United States reported 3.96 million new cases of COVID-19 over the past 28 days, followed by India and Iran, with over 1 million new cases each. Over this same period, the United Kingdom reported an estimated 869,000 new cases over the past 28 days, with 2,680 deaths.
Previous studies have shown that COVID-19 vaccines are highly effective against symptomatic infections with the Alpha variant, while also remaining effective against Delta variant symptomatic infections.
About the study
In the current study, the team of researchers characterized the Delta variant’s severity and compared it with that of the Alpha variant by determining the relative risk of hospital admission following infection. Further, they assessed whether links with hospital attendance outcomes were affected by an increase in vaccination rates.
The researchers conducted the study among all patients with COVID-19 in England between March 29, 2021, and May 23, 2021, who were infected with the Alpha or Delta variants. They compared the risk for hospital admission and emergency care attendance between patients with the Alpha or Delta variants.
In their work, the researchers found that most of the Alpha and Delta cases were reported in patients who were not vaccinated or received only the first dose of the vaccine. More specifically, about 74% of these patients were unvaccinated, whereas 24% were partially vaccinated, and only 2% were fully vaccinated.
Further, the team noted that the risk of getting hospitalized was two times higher in those with the Delta variant as compared to those with the Alpha variant. The emergency care attendance combined with hospital admission rates were also greater for patients with the Delta variant.
“To our knowledge, this study is the largest assessment of hospitalization risk for the delta variant using cases confirmed by whole-genome sequencing, providing important foundational evidence of increased risk compared with the alpha variant.”
The team added that the findings of their study are crucial for resource planning and policy decisions to mitigate the effect of the Delta variant in the U.K. The study also highlights the importance of getting vaccinated against SARS-CoV-2 to reduce the risk of hospitalization due to symptomatic COVID-19.