In countries where vaccines are scarce, the math of the pandemic remains unchanged. When the Indonesian authorities reported nearly 57,000 new cases on one day in early July — seven times as many as a month earlier — they also reported a record 1,205 deaths, bringing the country’s official toll from the pandemic to more than 71,000.
But in rich nations with ample vaccine supplies, public health officials are watching to see how mass inoculation campaigns have severed the link between case counts and pressure on health care systems. In Spain and Britain for example, cases have begun declining after the Delta variant drove numbers to concerning heights. But in other countries like Malaysia and Thailand, that climb is continuing.
In the United States, with about 93 million people eligible for shots who have chosen not to get them, experts say that a rise in cases this winter is inevitable.
The spread of the virus among the vaccinated is one of the most intensively watched in rich nations, and much remains unknown. Are there differences in breakthrough infections depending on which vaccine is administered? How long does it take for protection to fade? And when does the number of cases indicate a flood of patients that could overwhelm health care systems?
Public health officials are confident that there is little evidence to suggest that the virus has found a way to escape the main goal of vaccines: preventing serious sickness and death.
But there is also agreement that hundreds of millions of cases are now an inescapable part of our world of seven billion people. And with dramatic gaps in vaccination between wealthier and poorer nations, there is the extra challenge of funneling doses to those who remain unprotected. The W.H.O. on Wednesday called for a moratorium on booster shots until the end of September in an effort to help all countries inoculate 10 percent of their populations.
“We have to understand that this virus is now endemic and that we have to be thinking about our long-term strategies for dealing with it as a global phenomenon,” said Robert West, a professor emeritus of health psychology at University College London who is a subcommittee member of SAGE, a scientific body advising Britain’s government on policy.
“It is now inevitable that we’re going to be looking at tens, if not thousands, of deaths a year from this virus for the foreseeable future,” he said, “in the same way that we see deaths from other causes.”