Mr. Biden had said earlier this year that he wanted to see 70 percent of eligible Americans at least partly vaccinated by July 4. The country hit that goal on Monday, about a month late and only after the Delta variant began disrupting the progress touted by the president and public health officials.
There was no celebration of reaching the delayed milestone. Instead, the Biden administration has been in a race to encourage vaccine-reluctant and vaccine-refusing Americans to receive shots as caseloads rise in states with high unvaccinated populations.
“The vaccines are doing exactly what they are supposed to do when it comes to keeping you out of the hospital, out of serious disease, and certainly, preventing your death,” Dr. Anthony Fauci, the nation’s top disease expert, told reporters.
The White House has also struggled to put into context the threat of the Delta variant to those who are vaccinated. Experts say that infections in vaccinated people — so called breakthrough infections — are still relatively uncommon, and that even in those cases, the vaccines appear to protect against severe illness and death.
Nationally, new cases have reached an average of about 86,000 a day as of Monday, a dramatic jump from about 13,000 cases a month ago but still far fewer than in January. Hospitalizations have risen as well, but hospitalizations and deaths remain a fraction of their devastating winter peaks.
Mr. Biden’s pledge to donate 500 million Pfizer-BioNTech doses is by far the largest yet by a single country, but it would fully inoculate only about 3 percent of the world’s population. The United States will pay $3.5 billion for the Pfizer-BioNTech shots, about $7 apiece, which Pfizer described as a “not for profit” price — much less than the $20 it has paid for domestic use.
In a fact sheet released on Tuesday, the administration said that it would work with programs focused on the equitable distribution of vaccines, including Covax, to ensure that the doses arrive in the countries that are in the most need. But health officials in countries that have received some of the doses have already warned that additional funding is needed to train people to administer the shots and fuel vehicles that transport the vaccines to clinics in remote areas.