Moderna has pledged to put utmost efforts to increase the COVID-19 vaccine supply to South Korea for August and September and move up the supply schedule for September, the Korean government said Tuesday. 

The announcement came after a Korean government delegation of four high ranking officials visited the US pharmaceutical and biotechnology company’s headquarters over the delay in shipments of Moderna’s vaccine.

“Moderna apologized for the difficulties caused by the supply disruption to the Korean government and Korean people,” said Second Vice Health Minister Kang Do-tae, who led the government delegation.

According to the Ministry of Health and Welfare, Moderna explained that the supply disruption was caused by a problem at a manufacturing laboratory at its cooperative plant and the vaccine rollout for the July supply resumed after the problem was fixed.

The ministry said Moderna promised to notify the Korean government of the specific amount of its increased vaccine supply and shipment schedule before the end of this week.

According to the Health Ministry, the Korean delegation held a three-hour meeting with Moderna representatives including Chief Commercial Officer Corrine Le Goff, who agreed with Kang’s emphasis on building trust and expressed hope to continue to carry on a long term partnership with the Korean government.

Last week, the government announced that Moderna will be sending less than half of the 8.5 million vaccine doses it had promised to send over in August.

The delay dampened the country’s vaccine rollout, resulting in the government extending the period between the first and second jabs of two messenger RNA COVID-19 vaccines -- Moderna and Pfizer -- to cope with scarce supply. Since the beginning of this week, the administrations of the two shots have been now spread six weeks apart instead of the previous three to four weeks.

Moderna’s postponement in the vaccine shipments also previously happened in July when the US firm said it was not able to send over 1.96 million doses by the end of the month. Only 1.3 million doses of the promised amount ended up arriving in the Korea as of Aug. 7.

Korea’s contract with Moderna is set to bring in a total of 40 million doses of its COVID-19 vaccine to the country in 2021, according to the government. But just 2.45 million doses have been imported to the country so far.

The government has admitted that Moderna’s delays in the vaccine shipments are not violations of the contract between the two parties as the detailed schedule of vaccine supply is determined through negotiations. The exact terms of the contract cannot be released due to the confidentiality agreement, according to the government.

Although the repeated delays in the vaccine shipments have caused concerns that it could negatively affect the country’s vaccination drive, health authorities remained confident in reaching a 70 percent full vaccination rate by the end of October.

“In regards to achieving the goal of a 70 percent (vaccination rate), we already changed the vaccination plan after reflecting the uncertainty of vaccine supplies, so we believe the goal can be reached,” Kang said.

“If Moderna can ship over the vaccines under the renewed supply plan, it seems that the goal can be achieve more stably.”

According to the Korea Disease Control and Prevention Agency, 23 million people, or 44.9 percent of the population, have so far received their first shot, while nearly 10 million have been fully inoculated.