While the first shots against COVID-19 are rolling out in the United States, Britain and Canada, nearly a quarter of the world’s population likely will not have access to a vaccine until at least 2022, according to a new study. Even in a best-case scenario, the world does not have the manufacturing capacity to cover the entire global population. Wealthier countries made deals to buy the bulk of vaccine doses before the shots have even finished testing or received regulatory approval. Meanwhile, a partnership aimed at securing vaccines for low- and middle-income countries has so far reserved only a fraction of the doses it has promised to deliver. “Many governments in the poorest parts of the world are very, very concerned about the significant lag of when these vaccines are hitting these wealthy countries … and when they’ll actually be in developing countries,” said Kate Elder, senior vaccines policy adviser at the nonprofit Doctors Without Borders, who was not part of the study. First arrivals Last week, pharmaceutical and biotech partners Pfizer and BioNTech began delivering their COVID-19 vaccine in Britain. The first patients in the United States and Canada received their shots on Monday. A second…