Since the start of the pandemic, 832 children 5 and under have died of the virus, according to Brazil’s health ministry. Comparable data is scarce because countries track the impact of the virus differently, but in the United States, which has a far larger population than Brazil, and a higher death toll from Covid-19, 139 children 4 and under have died. And Brazil’s official number of child deaths is likely a substantial undercount, as a lack of widespread testing means many cases go undiagnosed, said Dr. Fátima Marinho, an epidemiologist at the University of São Paulo... “We can already affirm that the P.1 variant is much more severe in pregnant women,” said Dr. Ribas Freitas. “And, oftentimes, if the pregnant woman has the virus, the baby might not survive or they might both die.” Lack of timely and adequate access to health care for children once they fall ill is likely a factor in the death toll, experts said. In the United States and Europe, experts said, early treatment has been key to the recovery of children infected with the virus. In Brazil, overstretched doctors have often been late to confirm infections in children, Dr. Marinho said.