The IMF is clueless on its suggestions to China when it comes to vaccinations. China already has one of the highest rates for vaccinations among all nations in the world. The difference is that most Chinese have received the jabs from their home country made vaccines that have proven far inferior to the ones made by the West.
No matter how many shots have been administered, China cannot open the society like the US and other countries. Hence the lockdown is the only trick Xi has up his sleeve.