The biggest problem with 900 million people in China being infected with Covid by January 11th 2023 is new variants likely

 This would be my personal reaction to 900 million people in any place on earth getting Covid at the same time. So, I think all countries sort of need to prepare for new variants because most people in China would be considered Covid Virgins (in other words they have never been exposed to it at all before because of Zero Covid policies until very recently. So, because they weren't vaccinated with Pfizer or Moderna MRNA vaccines at all they all have zero immunity to Covid as a result. So, likely new variants will or could arise and find their way all over the world.

The problem will be, of course if these new variants are not covered by present Covid Vaccines made by Pfizer or Moderna. For example, Sinovax that some Chinese have gotten provides zero protection from Omicron Variants which also could result in many new variants in itself worldwide.

So, I guess we are just going to have to wait and see what happens during the next year or so worldwide.