> It was initially difficult due to lack of vaccines and interference from mainland China.
This was more a political decision from the Taiwanese government that it would not buy the BioNTech vaccine through the licensed distributor, because that distributor is a mainland Chinese company. Taiwan insisted on bypassing the Chinese distributor and buying directly from BioNTech, which would have been a violation of BioNTech's contract with the Chinese company. The reason the Chinese company had the license was that it invested in the development of the BioNTech vaccine very early on.
The Taiwanese government then blamed the PRC for supposedly blocking Taiwan from buying the BioNTech vaccine. The real issue was that given its politics, the DPP did not want to be seen to be relying on the mainland for vaccines.