>but poorer nations may hold out for future vaccines that remain stable at higher temperatures and only require a single dose.

Valid point, but I feel there's never been a better time for massively pushing this vaccine (after proper testing and regulatory approval, of course) to medium/low income countries.

Winter should make it much easier in managing the temperature range stability required for storing/shipping the vaccine, especially in countries around the equatorial region.

Doing it in late spring/summer will not be a good idea (assuming a better vaccine doesn't come out by then).