OBJECTIVES:

This study aims to compare COVID-19 average weekly infection fatality rate (AWIFR), investigate factors associated with COVID-19 AWIFR, and explore factors linked to the increase in COVID-19 AWIFR between two periods of Delta and Omicron variants.

METHODS:

We carried out an ecological study of 110 countries over the first twelve weeks during two periods of Delta and Omicron variant dominance, using publicly available databases. We calculated the AWIFR in aggregate data of twelve weeks in each period. Multivariable linear regression models were utilized to determine the factors associated with AWIFR and the increase in AWIFR between two periods.

RESULTS:

The Omicron period was found to have a lower AWIFR than Delta period, although it exhibited greater rates of average weekly infection and average weekly fatality. During Delta variant period, region, high government indicators, and proportion of the population fully vaccinated were significantly associated with a lower AWIFR, while high death rates caused by diabetes and kidney diseases were linked to higher AWIFR. During the Omicron variant period, countries with a high proportion of the population vaccinated with a booster dose had a significantly lower AWIFR, whereas YLDs caused by metabolism disorders, income level, and proportion of the population aged over 65 were adversely linked to AWIFR.

Over two periods of Delta and Omicron, we found a lower increase in AWIFR in countries with high levels of government effectiveness index and stringency index. In contrast, countries with high death rates caused by diabetes and kidney, and proportion of people aged over 65 were linked to a greater increase in AWIFR.

CONCLUSIONS:

Our findings suggest that government needs to keep fostering the rates of vaccine coverage, enhancing coordination between the intensity and duration of non-pharmaceutical interventions, strengthening interventions for chronic diseases, and implementing more assessments on metabolic disorders to alleviate the COVID-19 outcomes.