A systematic review of the impact of the Alpha and Gamma variants of concern on hospitalization and symptomatic rate of SARS-CoV-2

The hospitalization and symptomatic rates of Severe Acute Respiratory Syndrome Coronavirus Disease 2019 (SARS-CoV-2) are key epidemiological parameters affecting risk analyses conducted for the Canadian Armed Forces (CAF) during the Coronavirus Disease-19 (COVID-19) pandemic. As one of the criteria of a variant of concern (VOC) is that it affects disease severity, the authors sought to understand whether the Alpha and Gamma VOCs are significantly different in these two parameters than the original wildtype of SARS-CoV-2, the most prevalent in relevant areas of Canada as of study initiation. Searches for studies were conducted in Scopus and PubMed, and located through following citations and receiving studies from daily literature scans. For the hospitalization outcome, effect ratios relative to original wildtype were included. For the symptomatic ratio, the ratio itself for each variant was used. Analysis of age-related effects was of particular value, as CAF members are primarily adults under the age of 60. The firmest conclusion of this review is that the Alpha VOC comes with a higher relative risk of hospitalization compared to the original wildtype, most likely above 1.4, while unlikely to be above 2, with the balance of evidence being that the relative risk is not significantly modified by age. The evidence for Gamma is more limited, but the odds ratio may be above 2, and potentially much greater than that, especially for those 20-39 years of age. For both VOCs reports on symptomatic ratio differed on whether there was an effect, as well as its potential direction.