vaccine, or the one-and-done Johnson & Johnson shot. The threshold of half of all adult Americans fully vaccinated was reached in late May.
President Joe Biden has been pressing hard for Americans to get vaccinated ever since he took office in January but has faced stubborn resistance, especially in conservative parts of the country, with inoculations dropping off sharply in April.
The aggressive vaccination program had raised hopes of a return to some semblance of normal life this summer, but the plan was hindered by the Delta variant.
In an increasingly assertive approach, the Biden administration has asked all federal employees to get vaccinated or face Covid testing twice a week.