New datasets: 'Increased severity' of COVID-19 cases from UK variant

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Evidence continues to mount that the so-called UK variant is "likely" deadlier and results in more hospitalisations than non-variant COVID-19 cases, according to data released on a UK government website. MedPageToday reports that the study compiled research from major universities and studies and found "increased severity" of COVID-19 cases from the B.1.1.7 variant compared to "non-variants of concern," with B.1.1.7 cases anywhere from 30% to 70% deadlier than the original wild-type strain.

These concerns were initially raised in January, when the British government's New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG) presented initial data, suggesting cases with B.1.1.7 were likely deadlier than non-variant cases, but they noted then that "data will accrue in coming weeks, at which time the analyses will become more definitive."

The report detailed why these updated analyses were indeed more definitive, noting earlier reports using linked community testing and mortality data were all based on the same datasets, and thus the same biases.

"More recent analyses have added a wider range of data sets and been able to control for additional confounders, increasing confidence in the association of the [variant of concern] with increased disease severity," they wrote.

Of note, London School of Hygiene & Tropical Medicine found a relative hazard of death within 28 days was 1.58 (95% CI for variant-infected individuals versus non-variant-infected individuals, while Imperial College London found the mean ratio of case fatality for variant cases was 1.36 with a case-control weighting method.

Public Health England performed a matched cohort analysis, and found a "death risk ratio" of 1.65 (95% CI 1.21-2.25) for variant individuals versus non-variant individuals. Several other studies examined the effect of the variant on hospitalisation, with Public Health Scotland using the S-gene target failure as a proxy to determine variant cases.

They found risk of hospitalisation was higher among S-gene target failure cases versus S-gene positive cases (risk ratio 1.63, 95% CI 1.48-1.80). Research from Intensive Care National Audit and Research Centre (ICNARC) and QRESEARCH also found a higher risk of ICU admission for variant versus non-variant cases (HR 1.44, 95% CI 1.25-1.67).

However, the consensus was not unanimous, and the government included data from COVID-19 Clinical Information Network (CO-CIN), which found no evidence suggesting variants are linked with higher in-hospital case fatality rates. An analysis from Office for National Statistics (ONS) noted that while the hazard ratio suggested higher risk of all-cause mortality, "the number of deaths are too low for reliable inference."

The report also noted several limitations to the data, including representativeness, power, potential biases in case ascertainment, unmeasured confounders, and secular trends. They added that the majority of studies tried to control for confounding by nursing home status, but there was a potential for residual confounding due to unidentified nursing home residence in hospital datasets.

"There are potential limitations in all datasets used but together these analyses indicate that it is likely that … B.1.1.7 is associated with an increased risk of [hospitalization] and death compared to infection with non-[B.1.1.7] viruses," the authors concluded.

US Centres for Disease Control and Prevention (CDC) modelling in mid-January estimated the UK variant would become the dominant strain of COVID-19 in the US by the end of March. Another recent modelling study suggested incidence of variant cases are doubling every 10 days in this country.


Full MedPageToday report (Restricted access)


UK government data

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