According to a recent study, compared to the alpha variant, people infected with delta have double the risk of hospitalization.
As per the World Health Organization (WHO), four SARS-CoV-2 variants currently meet the definition of a variant of concern. The 4 variants – alpha, beta, gamma, and delta – have all shown an increase in virulence and transmissibility. The alpha variant, first discovered in the UK, was once the predominant strain across Europe and North America. However, since then it has been replaced by the contagious Delta variant. The highly transmissible variant has led to a new wave of infections across the world, along with an increase in breakthrough infections. Moreover, a preliminary study from Scotland had previously reported a doubling in risk of hospitalization with the delta variant compared with the alpha variant.
However, the Scotland study based their results on PCR test results and tested for a gene that is more common in the delta variant. Now, researchers in the UK have further evaluated the hospitalization risk. This is the first and largest study to use a whole-genome sequencing dataset.
The cohort study analyzed data from all patients infected with COVID-19 in England, between March 29 and May 23, 2021. A total of 43,338 COVID-19-positive patients were identified during the time period. Using individual-level data, the researchers conducted two analyses. First, they determined the risk of hospital admission within 14 days of infection with the delta variant. Then, the second analysis assessed the association in relation to a person’s vaccination status.
This large national study found a higher hospital admission or emergency care attendance risk for patients with COVID-19 infected with the delta variant compared with the alpha variant.
study authors
Unvaccinated Most at Risk
The study included 34,656 cases of the alpha variant and 8,682 cases of the delta variant. Although the proportion of delta cases was only 20% during the study period, it increased to 74% of new COVID cases by May 2021. Thus, showing the dominance of the strain in England.
The results showed that 1 in 50 patients underwent hospitalization within 14 days of a positive COVID-19 test. 2.2% of these patients had the alpha variant and 2.3% had the delta variant. However, once the researchers adjusted for risk factors of severe illness, the risk more than doubled with delta variant than alpha cases. Moreover, a large majority of COVID-19 cases (74%) occurred in unvaccinated individuals. The team observed similar results when they compared the risk of hospitalization in the unvaccinated patients.
According to the study authors, their research highlights the importance of vaccination in reducing outbreaks and hospitalizations. Multiple studies have shown the current vaccines as effective against the delta variant.
These findings should be considered for resource and policy planning in secondary care, particularly in areas where the delta variant is increasing and is likely to become the dominant circulating SARS-CoV-2 variant.
study authors
Reference:
Twohig, K. A., Nyberg, T., Zaidi, A., Thelwall, S., Sinnathamby, M. A., Aliabadi, S., . . . Gunson, R. (2021). 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. The Lancet Infectious Diseases. doi:10.1016/s1473-3099(21)00475-8
