South Korea received 1.26 million more doses of Moderna’s COVID-19 vaccine Sunday, a key supply for the country to continue on with its nationwide vaccination scheme.

With the latest shipment arriving at Incheon Airport on Sunday afternoon, Moderna fell some 2.8 million doses short of the 7.01 million promised by the first week of September.

The country is set to receive 2.55 million more doses Monday afternoon, a day late, but this is still more than 250,000 doses short of the amount promised by Sunday.

But as most of the vaccine supplies are still expected to reach Seoul within a manageable timeline, South Korea is still hopeful of meeting its goal of vaccinating 70 percent of the population with at least one shot by September and achieve herd immunity by November.

Before the Chuseok holiday, South Korean government aims to provide first shots to 36 million people.

As of Saturday’s end, a total of 29.87 million people, or 58.2 percent of Korea’s 52 million population, received their first shots of COVID-19 vaccines. Some 34 percent have been fully vaccinated.

Concerns remained high on whether Moderna will be able to fulfill its promise as agreed, given that it already broke its deal made in South Korea just weeks earlier.

Hong Jeong-ik, head of vaccine planning committee of the Korea Disease Control and Prevention Agency, said Wednesday that vaccinating 70 percent of the population with at least first dose by Sept. 18 could be difficult to achieve if a full supply was not guaranteed from Moderna.

The promise of 7.01 million doses was made after the South Korean government sent a delegation to Moderna’s headquarters in mid-August to seek a solution to the vaccine disruption. Moderna had notified Korea before that it would supply less than half of the 8.5 million doses scheduled for August due to production issues.

The supply disruption then forced Korea to lengthen the administration interval between the two doses from Pfizer and Moderna from the standard length of three or four weeks to six weeks, which raised concerns that longer interval would make the vaccines less effective.

Officials have been discussing whether to return the administration interval back to where it was after additional vaccines supplies were guaranteed from Moderna.