100% Delta Variant Detected Among Confirmed Cases... 28% Are Breakthrough Infections

Medical staff are preparing for COVID-19 testing at the temporary screening clinic in Seoul Plaza on the 20th. [Image source=Yonhap News]

[Asia Economy Reporter Lee Chun-hee] The COVID-19 Delta variant has been detected in all confirmed cases tested for variants over the past week. As the Delta variant spreads rapidly, the proportion of breakthrough infections among new confirmed cases has reached 27.6%.

The Korea Disease Control and Prevention Agency's Central Disaster and Safety Countermeasures Headquarters for COVID-19 announced on the 20th that an analysis of 3,245 domestic infection cases over the past week found the Delta variant in all cases.

Although this is not a full survey of all confirmed cases, it effectively means that the COVID-19 virus circulating domestically has all become the Delta variant. This is a significant change compared to the fourth week of June, when only 196 out of 642 analyzed cases (30.5%) showed major variants, and only 21 cases (3.3%) were confirmed as the Delta variant. From the fifth week of September to the first week of October, 15 and 8 cases respectively showed no major variants, but in this recent survey, all cases tested positive for the Delta variant.

As the Delta variant, known to have higher infectivity, severity, and fatality rates than the original COVID-19 virus or other variants, spreads, the number of 'breakthrough infection suspected' cases?those testing positive for COVID-19 more than 14 days after completing vaccination?is continuously increasing.

As of the 10th, the number of confirmed breakthrough infection suspected cases reached 16,972, an increase of 3,112 from 13,860 the previous week. This corresponds to 0.073% of the 23,174,126 fully vaccinated individuals, or about 73.2 cases per 100,000 people, up from 62.7 cases per 100,000 the previous week.

Breakthrough infection suspected cases, which were only 2 in April, surged to 8,911 last month, and 3,992 cases were confirmed by the 10th of this month, showing rapid growth. Notably, in the first week of October, 3,107 breakthrough infection suspected cases were confirmed among 11,248 total confirmed cases, accounting for 27.6%, significantly increasing their proportion among all confirmed cases.

The proportion of the Delta variant among breakthrough infection suspected cases is also continuously rising. Among 3,425 cases where variant virus analysis was completed, major variants were confirmed in 3,196 cases (93.3%), with the Delta variant accounting for the vast majority at 3,163 cases.

By vaccine type, the incidence rate of breakthrough infection suspected cases per 100,000 people was highest for Janssen at 243.5, followed by AstraZeneca (AZ) at 84.5, Pfizer at 49.9, and Moderna at 5.5. Among those who received heterologous vaccination?different vaccines for the first and second doses?the breakthrough infection rate was 61.5 per 100,000 people.