SEOUL: About 760,000 South Koreans who have received a first dose of AstraZeneca's COVID-19 vaccine will be offered Pfizer-BioNTech's vaccine as a second dose due to shipment delays by global vaccine sharing scheme COVAX, the government said.
Several countries, including Canada and Spain, have already approved such dose-mixing mainly due to concerns about rare and potentially fatal blood clots linked to the AstraZeneca vaccine.
A Spanish study found that giving a dose of the Pfizer-BioNTech shot to people who had already received the AstraZeneca vaccine is highly safe and effective, according to preliminary results.
About 835,000 doses of AstraZeneca's vaccine from COVAX were scheduled to arrive by the end of June, which South Korea planned to use mainly as a second dose for about 760,000 healthcare workers who had received a first dose in April.
The delayed shipment will arrive in July or later, while the country has used up its AstraZeneca reserves to meet stronger than expected participation in its vaccination campaign.
Over 27 per cent of its 52 million population have received at least one dose of a COVID-19 vaccine as of Thursday, and the country is on track to meet a target of 70 per cent by September and reach herd immunity before November.
South Korea said last month it will conduct a clinical trial that mixes COVID-19 doses from AstraZeneca with those from Pfizer-BioNTech and others.
It has so far run a trial in 100 healthcare workers to examine the formation of antibody and other immune effects, Korea Disease Control and Prevention Agency (KDCA) director Jeong Eun-kyeong told a briefing on Thursday.
South Korea reported 507 new infections by midnight on Wednesday, for a tally of 150,238 cases, the KDCA said, with a death toll of 1,996 since the pandemic began.