Delta COVID-19 variant doubles risk of hospitalization compared to Alpha strain, Scottish study finds

A study out of Scotland has found the Delta COVID-19 variant carries double the risk of hospitalization compared to the Alpha strain, particularly in patients with five or more comorbidities. Scotland had determined that the Delta variant became the dominant strain in the country about a month ago. 

Using the country’s COVID-19 surveillance program, researchers on behalf of Public Health Scotland analyzed data to investigate risk of hospital admission and estimate vaccinate effectiveness at preventing hospital admissions among likely Delta variant cases. The study was published Monday in The Lancet.

During the study period, which spanned from April 1 to June 6, 2021, there were 19,543 coronavirus cases, 377 of which required hospitalization. Of those hospitalizations, 134 cases were S gene-positive. In earlier analysis, researchers had determined that 97% of S gene–positive cases sequenced in Scotland were the Delta variant, and 99% of Delta variants were S gene positive. S gene-negative cases were classified as Alpha variant infections. 

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In the data, the researchers noted that S-gene positive cases occurred in all ages, but more so in younger children than compared to the Alpha variant. They also found that S gene-positive cases were associated with an increased risk of COVID-19 hospitalization admission when compared to S gene-negative cases, and that a greater number of relevant comorbidities increased the risk. 

Both the AstraZeneca COVID-19 vaccine and the Pfizer-BioNTech jab were shown to cut risk of infection and hospitalization due to the Delta variant, but protection against infection fell as compared with the Alpha variant.

However, the researchers noted that the analysis was observational in nature, and estimates of vaccine effectiveness “need to be interpreted with caution.” They also said there were insufficient numbers on hospitalization admissions and the variants “to compare between vaccines in this respect.” 

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“In summary, we show that the Delta VOC in Scotland was found mainly in younger, more affluent groups,” the researchers wrote. “Risk of COVID-19 hospital admission was approximately doubled in those with the Delta VOC compared to the Alpha VOC, with risk of admission particularly increased in those with five or more relevant comorbidities.”