South Korea mistakenly opened up COVID-19 vaccine appointments on Monday for tens of thousands of people who were not yet eligible, leading to a slew of cancellations the same day.

Pfizer vaccine appointments became available to employees in their 20s at some of the country’s largest tech and semiconductor firms and banks, according to industry sources. The news quickly spread through social media, with many people working in the same fields proceeding to make appointments.

Later, the Korea Disease Control and Prevention Agency admitted in a statement that it had erroneously included additional people on the eligibility list. “The vaccine appointments were intended for health care personnel at these companies. In the process of coordinating the schedule, the information of other employees was wrongly added to the pool,” it said.

The agency said there were roughly 20,000 such ineligible people who scheduled appointments for Pfizer shots during the morning hours -- and that all of them would be canceled in the next few hours.

The mix-up led to disappointment, and some frustration, for the young working Koreans.

“When my colleague told me we were also up for the vaccines I was so happy. I thought people my age were far back in the priority line,” said a 29-year-old employee at one of the companies, who wished to remain anonymous. “Now it’s being taken away.”

One post on Blind, a professional networking app, said, “Why cancel? If it’s their mistake then they should own up to it and just let us have it.”

On the bright side, the fiasco attests to how eager young people are to get vaccinated, according to Dr. Jung Ki-suck, a former Korea Centers for Disease Control and Prevention Agency director. “I think once vaccines become available, the majority of Koreans will want to get it,” he said. “Like I’ve said we’re one of the least vaccine-resistant countries in the world.”

In June the only people under the age of 30 who are eligible for the vaccine are essential workers and military personnel who couldn’t get the AstraZeneca vaccine due to the changes in age recommendations, according to a senior official at the national health agency.

He said the agency did not plan on extending vaccinations to younger age groups this month. The eligible occupational categories now are police, firefighters, preschool and primary school teachers, and group home workers.

As current vaccination efforts are targeting more vulnerable people in their 60s and older, and will proceed in descending order of age, younger people will have access to the vaccine later in the summer.

By Kim Arin (arin@heraldcorp.com)