The omicron strain of Covid-19 is at least 40% more lethal than seasonal flu, according to Japanese scientists, underscoring the potential danger of lifting pandemic curbs too quickly and underestimating the virus’s ongoing health risks.
The case fatality rate of omicron in Japan, based on cumulative excess deaths and the number of infections since January, was about 0.13%, according to an analysis by scientists who advise the country’s health minister. While that is significantly lower than the 4.25% case fatality rate from earlier in the outbreak, it’s still higher than the 0.006% to 0.09% seen with seasonal flu, they said.
Countries around the world have been relaxing mitigation measures, from mask mandates to testing requirements, and pushing for a return to normal life. The public has grown tired of restrictions and the reduced severity of omicron has reassured many that the rules are no longer essential. While Japan hasn’t formally downgraded the condition, it is easing border restrictions and quarantine periods for travelers, essential workers and close contacts of positive cases to keep the economy going.
The decline in mortality with omicron could reflect both the reduced virulence of the strain, particularly in comparison to the delta variant, and the benefits of vaccination, the researcher said. The findings show the importance of putting control measures in place before vaccines are fully distributed, they said.
More study is needed to determine the impact of the easing once all the restrictions are lifted, Takaji Wakita, chair of the health ministry’s advisory board, said at a briefing Wednesday night where the data was presented. The current information was obtained when most of the pandemic curbs were still in place, he said.
The study, which hasn’t been peer-reviewed or published in a medical journal, has several limitations, including differences in the way the data was collected that makes cross-comparisons difficult, Wakita said.
“Still, there’s a considerable difference in mortality,” though the arrival of omicron has narrowed the gap between Covid and influenza, he said.
The omicron-fueled wave has prompted some regions in Japan to seek states of quasi-emergency that restrict the operations of bars and restaurants. Currently, 31 of the country’s 47 prefectures are under those measures until March 6. Some areas, including Osaka and Kyoto, have sought to extend them, while others have asked to have them lifted, national broadcaster NHK reported Wednesday.