US Researchers: "Omicron Severe Risk as Deadly as Delta"

[Asia Economy Reporter Kang Nahum] A study in the United States has found that the COVID-19 Omicron variant can be as deadly as previous variants such as Delta.

A research team of four infectious disease experts, including Zachary Strasser from Massachusetts General Hospital, published their analysis on the Nature Portfolio journal website on the 2nd. They analyzed hospitalization and death data of over 130,000 COVID-19 patients in Massachusetts.

The researchers argued that confounding variables (third factors that distort causal relationships) affecting the risk level of variants differed significantly between the early spread of COVID-19 and now, and may continue to change. They emphasized that reflecting these differences is necessary for accurate comparisons.

The confounding variables highlighted in the study included the introduction of new vaccines and treatments, implementation of various public health strategies, patient vulnerability based on demographic characteristics, and the Charlson Comorbidity Index (CCI) indicating the number of other diseases.

The study utilized data from 131,174 patients confirmed between December 1, 2020, and February 28 of this year.

All patients were divided into four groups based on the time of diagnosis: winter 2020, spring 2021, Delta spread period, and Omicron spread period. Patients confirmed from December last year to February this year were classified as Omicron cases. A simple comparison of the four groups showed that the hospitalization rate for Omicron patients was 12.7%, lower than the previous three groups including Delta (14.2% to 15.8%).

The probability of death in hospitals was also lower for Omicron. However, when accounting for confounding variables, the risk levels differed.

The risk of hospitalization with Omicron was slightly higher than in winter 2020 but slightly lower than in spring 2021. The risk of death was very similar to winter 2020 and Delta.

The researchers explained these results as "(regardless of variant type) the risk of hospitalization and death during the comparison periods was almost the same." However, they noted several limitations in the study, such as vaccination statistics being limited to Massachusetts, and excluding patients who self-tested or did not get tested at all.