ASAP. Hard to morally justify vaccinating e.g. 45 year olds (covid mortality rate of 0.4%) here, when in other parts of the world there are unvaccinated 75 year olds (covid mortality rate of 15%).
Happily, I think vaccine production is ramping up all the time, and the cost is not actually that high on the scale of things (for the wealthier countries to fund vaccines for the rest of the world would cost a tiny fraction of the losses caused by coronavirus so far), so I think the third world should get vacinated fairly quickly even if the first world heavily prioritises its own people.
I suppose the real danger then is new variants rendering existing vaccines obsolete, but even if that does happen we'll have much more vaccine infrastructure in place, so would hopefully be able to churn out a new one fairly quickly.