First dose of Chinese COVID vaccine offers little protection, Chile discovers

More than 7.6 million people, half of Chile’s adult population, have already received at least one vaccine dose, most made by the Chinese drugmaker, making the country a real-world testing ground for a vaccine that Beijing is supplying to countries across the developing world. The problem, public-health officials say, was that people in general overestimated the effectiveness of the vaccine after only one of the two recommended doses and moved to ease up on pandemic-control restrictions too soon. “With one dose, we know the protection is very weak,” said Claudia Cortés, an infectious disease expert at the Santa Maria Clinic in Santiago, where about 10% of the Covid-19 patients at her hospital have received one shot. “It was not clearly explained that you need two doses—that you need to wait.”... On Friday, Chilean authorities released the results of a study of 10.5 million people, showing the vaccine was 16% effective against infection after one dose and 67% effective after a second dose. The study also found it to be 80% effective in preventing death from Covid-19 two weeks after a second dose.