President Biden took office with a detailed plan to combat Covid-19, including accelerating vaccinations, reopening schools, and selling a massive stimulus package to assist embattled state and local officials in keeping the virus under control.

The pandemic’s course has repeatedly forced the administration to deviate from that initial plan. Administration officials have been able to adapt quickly to changing circumstances at times. In other cases, they, by their own admission, failed to predict how the virus would evolve and how Americans would react.

Officials overestimated their ability to push vaccinations through incentives and mandates, and public-health experts say the emphasis on shots came at times at the expense of testing, therapeutics, and other mitigation measures that could have better prepared the country for highly transmissible variants like Delta and Omicron.

One year into Mr. Biden’s presidency, roughly two-thirds of eligible Americans have been fully vaccinated, and officials have made significant progress in reducing disparities in access to shots and increasing genomic sequencing to detect changes in the virus. In interviews, the president’s top health advisers say the country has passed the worst of the pandemic by 2020 and that the tools to avoid measures like lockdowns are now in place. However, the United States is once again experiencing a surge in cases, with some schools temporarily returning to virtual learning this month, businesses dealing with staffing shortages, and hospitals in many parts of the country overburdened.

As the virus persists, the president and his administration are working to increase access to rapid tests and high-quality masks in order to persuade a tired American public that they can reduce the disruption to daily life caused by Covid-19.

Mr. Biden’s early poll numbers were boosted by early confidence in his handling of the pandemic. In July, the president stated that the United States was on the verge of declaring independence from the virus.

However, his approval ratings plummeted in the summer as the Delta variant took hold and the United States exited Afghanistan in a shambles. Mr. Biden is still recovering. According to a Pew Research Center poll conducted this month, only 44 percent of Americans are confident in Mr. Biden’s ability to handle the pandemic, down from 65 percent in March.

The administration moved quickly to set up mass vaccination sites across the country, called in the National Guard to help administer shots, and used the Defense Production Act to speed up vaccine production. In response to high demand, the United States administered 200 million shots in Mr. Biden’s first 100 days in office.

The president also expanded testing access, extended a mask mandate on federal property and public transportation, and signed a $1.9 trillion Covid-19 relief package that included funding for vaccine distribution, assistance in reopening schools safely, and money for businesses and families.

Nonetheless, the administration was overconfident that its early vaccination campaign would restore normalcy to American life. In May, the Centers for Disease Control and Prevention recommended that fully vaccinated people no longer need to wear masks in most settings—but research revealed that vaccinated people could transmit the Delta variant, so the recommendation was reversed.

Schools were also slow to reopen in some areas, despite giving priority to teachers for vaccines. Republicans accused Mr. Biden of caving in to teacher union pressure. The president stated that it was critical for schools to reopen safely, though some schools stated that they needed more direction. Most schools were back in session by the fall, but disagreements over how they should operate persisted.

Under the rules, all employers with 100 or more employees would be required to require their employees to be vaccinated or tested on a weekly basis. In addition, Mr. Biden mandated Covid-19 vaccines for federal employees and contractors. The effort was later thwarted when the Supreme Court blocked the rules for private employers while upholding a requirement for many health workers. Lower courts have halted mandates for federal employees and contractors, and legal proceedings are still ongoing. According to administration officials, the Omicron variant’s impact on the United States would have been greater if another contentious vaccination decision had not been made. After data from Israel showed the shot’s waning efficacy among vaccinated people, top US health officials backed a booster plan in August, just a month after the CDC said boosters were unnecessary.