Why Are COVID-19 Fatality and Severity Rates Higher This Winter Than in Summer?

[Asia Economy Reporter Byun Seon-jin] The fatality rate and severity rate of the 7th wave this winter have been found to be higher than those of the previous summer wave (6th wave). Experts interpret this not as the virus becoming more virulent, but as meaning that there are more 'hidden infected individuals.' The possibility of the fatality rate rising further depends on how quickly the Omicron subvariant BN.1, which has been recently spreading, expands and whether high-risk groups receive vaccinations.

On the 15th, the Central Disease Control Headquarters monitored COVID-19 confirmed cases for two weeks during the fourth week of November (20?26). The fatality rate was 0.08%. The fatality rate is calculated by dividing the number of deaths by the number of confirmed cases and then multiplying by 100. The COVID-19 fatality rate hit a record low of 0.04% in July, rebounded to 0.07% in September and October, and rose again as the 7th wave began in winter.

Since the scale of the 7th wave is still growing around mid-December, if we consider late November as the mid-phase of the wave, the fatality rate for the fourth week of July (17?23), which showed a similar pattern of confirmed cases in the previous summer, was 0.03%, less than half of the current rate. The severity rate was 0.17%, more than five times higher than the same period (0.03%). The fatality rate increases sharply among high-risk groups. The fatality rate for those aged 80 and above was 2.05%, while it was 0.47% and 0.12% for those in their 70s and 60s, respectively. In the first week of December, 88.3% (392 people) of critically ill patients were aged 60 or older, and 92.2% (47 people) of deaths were also in this age group.

Why Are the Fatality and Severity Rates Higher in the 7th Wave Compared to Summer?

So why is the fatality rate higher in the 7th wave than in the 6th wave? The Omicron variant BA.5, which led the summer wave, is still dominating this winter's wave. This means the virus has not become more virulent. Experts analyze that the decrease in the number of COVID-19 tests has significantly reduced the number of confirmed cases, which is the denominator (Baek Soon-young, Professor Emeritus at Catholic University Medical School). Professor Kim Woo-joo of Korea University Guro Hospital's Infectious Diseases Department estimates that the actual number of confirmed cases, including hidden infections, is likely in the mid to high 100,000s.

The Fatality Rate Could Rise Further... Is There a Solution?

There are variables that could increase the fatality rate. As of the 10th, the detection rate of BA.5 was 60.5%, down from 67.8% the previous week, while BN.1 rose to 17.2% from 13.2% the previous week. BN.1, a sublineage of BA.2.75, also known as the 'Centaurus variant,' has gradually expanded its presence with 7.6% in the third week of November, 7.7% in the fourth week, and 13.2% in the fifth week. Lim Sook-young, head of the Central Disease Control Headquarters Situation Management Team, said, “BN.1 shows immune evasion characteristics. Although its growth rate is not faster than BA.5, it is believed to be partially influencing the current increase in domestic confirmed cases.” High immune evasion means reinfections occur more easily, and actual suspected reinfection cases increased to 14.7% in the fifth week of November from 13.3% the previous week.

The health authorities regard the infection and severity prevention effects of the currently administered updated vaccines as effective and urge people to participate in vaccination. The updated vaccine coverage rate among high-risk groups aged 60 and above is still low at 26.0%. Hwang Kyung-won, head of the Vaccination Planning Team at the COVID-19 Vaccination Response Headquarters, said, "Since BN.1 is a subvariant of BA.2.75, which is an Omicron variant, it is expected that the currently administered bivalent vaccines will be sufficiently effective." The health authorities also judge that antibody treatments such as Evusheld and Bebtelovimab, as well as antiviral drugs like Paxlovid and Lagevrio, will be effective in treating COVID variants with high immune evasion.

This content was produced with the assistance of AI translation services.