They basically got cocky. They gambled that their prior infection controls could keep them safe until they could acquire vaccines on their own terms.

Now many of those countries are finding out that what worked last year doesn’t work for the Delta variant. When other developed countries are talking about boosters these countries are scrambling to fully vaccinate their population and because they are so late to the game they’re likely 6-12 months behind.

Now if we don’t get yet another variant that requires a different vaccine/booster they might be fine. But they might also find out that by the time they’ve vaccinated for the original strain the vaccine is no longer effective.