From South America to the Middle East, a handful of countries are administering a second booster shot against Covid-19 as governments in many parts of the world grapple with a surge in coronavirus cases.
The use of a second booster, or typically a fourth shot, is emerging for different reasons, health experts say. In Latin America, delivering a second booster allows Chile and Brazil to reinforce less-effective Chinese-made vaccines on which they relied. Israel, meanwhile, is seeking higher levels of protection with a fourth dose of Pfizer Inc.’s vaccine after those with a third began losing immunity within a few months.
