Aug. 4 (UPI) -- South Korea is reporting its first cases of the Delta Plus COVID-19 variant. Both are "breakthrough cases" involving patients fully inoculated against the novel coronavirus.
The mutation of the highly infectious Delta variant was first confirmed in a South Korean man in his 40s on July 26. The man did not travel overseas, local network MBC and Korea Economic Daily reported Wednesday.
The man's son, whose age was not disclosed, also was infected with COVID-19 but was not confirmed for the Delta Plus variant, according to reports.
South Korea's second Delta Plus variant patient is a South Korean man in his 50s, who traveled to the United States and returned to Korea on July 23.
Local authorities said both patients had received two doses of the AstraZeneca vaccine.
Health officials have also identified the strain of Delta Plus variants for each patient. The man in his 40s was infected with the AY2 strain of Delta Plus, the man in his 50s with the AY3 strain, reports said.
Scientists continue to investigate whether Delta Plus is more contagious than other variants. The Indian SARS-CoV-2 Genomics Consortium has said that Delta Plus is unlikely to be more transmissible than Delta, according to the Washington Post.
Korea has been ramping up vaccinations after a slow initial rollout.
South Korean Prime Minister Kim Boo-kyum said Wednesday during a meeting of the Central Disaster and Safety Countermeasures Headquarters that the number of people who received their first dose of a COVID-19 vaccine surpassed 20 million by Tuesday.
Kim also said vaccinations are gaining momentum.
"In the current situation where infection is spreading across the country, the fundamental answer to overcoming the crisis is to form herd immunity as soon as possible through vaccinations," the prime minister said, according to Korea Economic Daily.
Kim also said in August about 28.6 million new doses of COVID-19 vaccines are expected to reach the population.
South Korea reported 1,723 new cases of COVID-19 on Wednesday, adding to a total caseload of 203,926 since the start of the pandemic.