Anthony S. Fauci, the government’s top infectious-disease expert, on Tuesday called the highly contagious delta variant of the coronavirus the “greatest threat” to the nation’s efforts in eliminating covid-19, the disease the virus causes.

Delta, which was first detected in India, is “unquestionably” more transmissible than other common coronavirus variants, Fauci said in a White House news conference. It is associated with “increased disease severity, as reflected by hospitalization risk,” he said.

The United States has fully vaccinated 150 million people against the coronavirus, marking a major milestone in the fight against the pandemic. But the nation is expected to fall short of President Biden’s goal of getting at least one shot into the arms of 70 percent of U.S. adults by the Fourth of July, and new variants are spreading rapidly.

Here are some significant developments:

  • After conceding that the country won’t reach its July 4 vaccination goal, the White House announced a new objective: ensuring that 70 percent of Americans age 27 and up receive at least one vaccine dose by the end of the holiday weekend.
  • Over 45 percent of U.S. residents have completed their vaccination schedule, a significant improvement but nowhere near the threshold necessary to snuff out the virus in the country. Rates among the youngest adults continue to lag.
  • More than 150 health-care workers who did not comply with a Texas-based hospital system’s vaccine mandate were fired or resigned, the latest chapter in an ongoing fight between Houston Methodist and its employees.
  • A coronavirus outbreak at a Florida government building killed two people and hospitalized several others who were unvaccinated against the virus, a county official said.
  • Russian President Vladimir Putin warned that infection rates are worsening in some regions of the country, a shift in messaging after he repeatedly downplayed the severity of the latest wave.
  • Philippine President Rodrigo Duterte has threatened to arrest citizens who don’t want to get vaccinated, even though the official policy of the country is that inoculations are voluntary.
  • The United States on Monday reported a seven-day rolling average of 11,254 new infections. The number of new daily cases has fallen by about 22 percent.