Reinfection Rate and Effective Reproduction Number Increase from Last Week... BA.5 Detection Rate at 87.9% (Update)

Weekly Confirmed Cases with Estimated Reinfection Rate at 6.11%
Infection Reproduction Number Increased by 0.04 from Previous Week to 1.18
BA.5 Domestic Infection Detection Rate 91.5% · Overseas Inflow 80.4%

[Image source=Yonhap News]

[Asia Economy Reporter Kim Young-won] Both the COVID-19 effective reproduction number and the proportion of suspected reinfection cases among weekly confirmed cases have slightly increased compared to the previous week. The detection rate of Omicron BA.5 was higher in domestic infection cases than in imported cases.

On the 16th, Baek Kyung-ran, Commissioner of the Korea Disease Control and Prevention Agency (KDCA), stated at the regular briefing of the Central Disease Control Headquarters, "Although the doubling trend that occurred every week in early July has slowed down, as of mid-August, the increasing trend has not yet subsided. The effective reproduction number also slightly increased from 1.14 last week to 1.18, marking over seven consecutive weeks above 1."

The effective reproduction number exceeded 1 in the fifth week of June and increased for two weeks before declining after the second week of July (1.58). However, it shifted back to an increasing trend in the second week of this month (August 7?13), four weeks later. An effective reproduction number above 1 indicates epidemic spread, while below 1 indicates a decline.

As of the 7th, the cumulative suspected reinfection cases include 183,306 people infected twice and 311 people infected three or more times. The proportion of suspected reinfection cases among weekly confirmed cases was 6.11%, up from 5.43% the previous week. This ratio was 3.71% until the second week of last month but has been in the 5?6% range since the third week. Among the twice-infected cases, 40.45%, and among the thrice-infected, 35.0% are minors under 18 years old.

The domestic detection rate of the Omicron BA.5 variant, which is driving the resurgence, was 87.9% from August 7 to 13, an increase of 11.6 percentage points from 76.3% the previous week. Among these, the detection rate in domestic infections was 91.5%, higher than the 80.4% detection rate in imported cases. Previously, the detection rate in imported cases was higher than in domestic infections.

During the same period, an additional 2,240 cases of Omicron BA.5, 31 cases of BA.2.75, 18 cases of BA.2.12.1, and 26 cases of BA.4 were detected. Lee Sang-won, head of the Epidemiological Investigation and Analysis Team at the Central Disease Control Headquarters, explained, "While BA.2.75 is certainly a new variant, it does not yet appear to be overwhelmingly transmissible compared to BA.5. Scholars have suggested that BA.2.75 might act as a new immune evasion after BA.5, but currently, BA.4 and BA.5 remain somewhat more significant challenges than BA.2.75."

60 and Older: Fatality Rate Decreased but Deaths Increasing

The health authorities urged caution as the proportion of high-risk individuals aged 60 and older among confirmed cases has increased. In the first week of August, the 60+ age group accounted for 20.2% of all confirmed cases, rising to 21.7% last week.

According to the Central Disease Control Headquarters, since the fourth week of January this year when Omicron began to spread, the COVID-19 fatality rate among those aged 60 and older has been steadily decreasing: from 4.54% in the first week of January → 0.50% in the fourth week of March → 0.33% in the third week of June → 0.15% in the fourth week of July.

However, the number of deaths in this age group, which had decreased as the Omicron wave subsided, began to rise again from last month due to the resurgence. COVID-19 deaths among those aged 60 and older surged from 341 in the first week of January to 2,387 in the fourth week of March, then decreased to 69 in the third week of June. Since then, the number has been increasing to 158 in the fourth week of July and 303 in the second week of this month.

Commissioner Baek said, "More than six months have passed since the third vaccination, and due to the increase in cluster infections in vulnerable facilities, the number and proportion of confirmed cases aged 60 and older at high risk of severe illness continue to rise. This is a time when not only the health authorities, facility managers, and medical personnel but also the elderly themselves need to be highly vigilant and practice safe behaviors to protect high-risk groups."