KAMPALA, Uganda (AP) — Some of the most desperately poor countries in the world are seeing a two-headed crisis: a surge in COVID-19 cases and a critical shortage of vaccine. Fears are running high in African nations such as Zimbabwe, Zambia and Uganda. Africa’s 1.3 billion people account for 18% of the world’s population. But the continent has received only 2% of all vaccine doses administered globally. And some African countries have yet to dispense a single shot. Health experts and world leaders have repeatedly warned that even if rich nations immunize all their people, the pandemic will not be defeated if the virus is allowed to spread in countries starved of vaccine.