Before June, China vaccinations may peak at 15 million per day
That implies production capacity of:
450 million doses per month
5400 million doses per year
Given this amount of production capacity and zero cases, China could continue with large scale vaccine exports in the next few months.
On a separate note, I also noticed that Serum Institute of India is looking to build a new factory with a capacity of 1000 million doses for $400 million. That is dirt cheap compared to the economic costs of the pandemic.