The leader of the World Health Organization (WHO) is calling on wealthy nations to issue a moratorium on COVID-19 boosters and instead provide initial vaccine doses to poorer nations. WHO Director-General Tedros Adhanom Ghebreyesus, who has frequently said that wealthier countries should hold off on booster shots, said Wednesday that these nations need to wait until the end of the year. “I will not stay silent when companies and countries that control the global supply of vaccines think the world’s poor should be satisfied with leftovers,” Tedros told a news conference, adding that he is “appalled” that some comments by a leading pharmaceutical association this week about the global supply chain being strong enough to support both vaccines and booster shots. Israel, Britain, Denmark, France, Germany, Spain, and the United States recently started either implementing a booster program or are working on doing so. “A month ago, I called for …