The National Vaccine Institute (NVI) has apologised for slow Covid-19 vaccine procurement and says it is prepared to hold talks to join the Covax global vaccine sharing scheme.

The apology came after the government faced criticism over its failure to procure enough vaccines as infection numbers continued to soar, with a record 13,002 new cases reported on Wednesday.

NVI director Nakorn Premsri said the agency tried to contact vaccine manufacturers in August last year and place advance orders even though the vaccines were in research trials.

He said that vaccine procurement plans must go before a committee chaired by the permanent secretary for public health.

Advice must also be sought from the government's legal advisory agency before an agreement is signed, he added.

"This has led to public feeling that the vaccine procurement may not meet the target. It's all about those impediments and constraints. I apologise to the public," Dr Nakorn said.

He also said the NVI has prepared for talks to join Covax, an international vaccine-sharing scheme administrated by the World Health Organisation.

"The NVI aims to receive vaccines from Covax next year," he said.