Is Omicron really mild? - Comparative analysis of comorbidities and
disease outcomes associated with SARS-CoV-2 Omicron (B.1.1.529) and
Delta (B.1.617.2) variants
Abstract
Introduction Multiple variants of SARS-CoV-2 from Alpha to
Omicron have an estimated 6.1 million deaths globally till date.
However, variants have been found to vary in transmissibility and
severity. The present study deals with comparison of morbidity and
mortality with SARS-CoV-2 Omicron (B.1.1.529) and Delta (B.1.617.2)
variants. Methods An observational retrospective cohort study
was conducted on a cohort of laboratory confirmed patients of SARS-CoV-2
diagnosed by qRT-PCR of nasopharyngeal swabs in periods; April-2021 &
January-2022; that were sequenced and variants were recorded. Patients
were invited for a telephonic interview after voluntary and informed
consent was obtained from each participant wherein, the demographics,
co-morbidities, oxygen requirement and mortality outcomes of the
patients were enquired about. Results A total of 200 patients,
with 100 from each period were included in the study. Major
comorbidities in patients included hypertension, diabetes mellitus and
pulmonary disease. Patients who succumbed to the Delta variant (26%)
were higher as compared to the Omicron variant (10%); with the elderly
(68 ± 9.7 years) having mortality during the Omicron variant. A
significantly increased risk for mortality was observed in comorbidities
in both Delta and Omicron variants with hypertension (OR:1.3;5.44),
diabetes mellitus (OR:0.99;1.94), chronic pulmonary disease
(OR:1.6;2.25), chronic kidney disease (OR:3.18;0.89), and smoking
(OR:1.74;1.55). Conclusion The study concluded that the Omicron
has potential of high transmissibility and milder disease for the
population by large, however, it is not a milder strain for patients
with comorbidities having a higher risk of adverse outcomes than that of
the previously dominant Delta variant.