In the last week, leading epidemiologists from respected institutions have, through different methods, reached the same conclusion: About 85 to 90 percent of the American population is still susceptible to SARS-CoV-2, the virus causing the current pandemic.

The number is important because it means that “herd immunity” — the point at which a disease stops spreading because nearly everyone in a population has contracted it — is still very far off.

WASHINGTON — Top White House officials pressured the Centers for Disease Control and Prevention this summer to play down the risk of sending children back to school, a strikingly political intervention in one of the most sensitive public health debates of the pandemic, according to documents and interviews with current and former government officials.

As part of their behind-the-scenes effort, White House officials also tried to circumvent the C.D.C. in a search for alternate data showing that the pandemic was weakening and posed little danger to children.

The world still lacks a proven coronavirus vaccine, but that has not stopped Chinese officials from trying to inoculate tens of thousands, if not hundreds of thousands, of people outside the traditional testing process. Three vaccine candidates are being injected into workers whom the government considers essential, along with many others, including employees of the pharmaceutical firms themselves.