The gathering research into the variant throws into disarray the country’s plans to return to offices and schools this fall, and revives difficult questions about masking, testing and other precautions that Americans had hoped were behind them.
Government officials and scientists alike are gravely concerned that the findings may shake faith in the vaccines, hobbling the nation’s lagging immunization campaign, should Americans infer incorrectly that the shots are not effective.
Concerned by the lagging campaign, President Biden has ordered that all federal employees be vaccinated or face weekly virus testing. Support for vaccination mandates is growing among some corporations and in some parts of the country.
The evolving research into the Delta variant has humbled scientists worldwide, who now confront fresh questions about the virus they had not considered.
They do not fully understand the circumstances that may increase the odds of a breakthrough infection, for example, nor who may be most at risk. They do not know for certain that the Delta variant causes more severe disease in the unvaccinated who become infected, although early data suggest it does.
“We spent so much time and energy and treasure trying to figure out this damn virus last year, and how it works and all the things it does,” said Dr. Robert Wachter, chairman of the Department of Medicine at the University of California, San Francisco.
Learning just how different the Delta variant is from the original virus is “just jarring,” he added. “The brain doesn’t like to keep being jerked around like this.”