There were many reasons for delays in Covid-19 vaccinations, according to Prime Minister Prayut Chan-o-cha, who apologised for it.

Prayut said on Tuesday that the government was receiving small lots of ordered vaccines, not huge lots at a time, and vaccinations stopped at the inoculation stations that used all their vaccine stocks.

Vaccine deliveries took time because they had to wait for production and quality checks. Many countries faced the same problem, he said.

Besides, vaccinations were accelerated for at-risk people in outbreak areas including those in Bangkok to control Covid-19 and maintain the operations of factories. That affected some previous vaccine registrants, the prime minister said.

Vaccination registrants whose appointments were postponed did not have to register again and their places in queues would be kept, Prayut said.

"I must apologise for the problems that happened and I take all the responsibility," he said.