The U.S. public health emergency declared in response to Covid-19 comes to an end Thursday more than three years after the pandemic began.

The Biden administration‘s decision to end the emergency comes as deaths and hospitalizations have declined dramatically due to the availability of vaccines, antiviral treatments and widespread exposure to the virus.

Deaths from Covid have fallen to their lowest point since March 2020, when the rapid spread of the virus in the U.S. overwhelmed the health system and lead to widespread shutdowns of schools, businesses and public venues.

Hospital admissions from the virus have also fallen to the lowest level since the U.S. started tracking the data in August 2020.

The end of the emergency will bring significant changes in how the U.S. responds to the virus. Hospitals will lose flexibility to rapidly add bed capacity if patient admissions surge, and the Centers for Disease Control and Prevention will scale back its efforts to track the virus.

After the emergency ends, the CDC will no longer be able to compel labs to report Covid test results. The agency does not have the authority to compel U.S. states to report new cases.

CDC Director Dr. Rochelle Walensky, who will step down at the end of June, warned Congress last week that the agency still has to negotiate data-sharing agreements with individual jurisdictions, a time-consuming process that puts the nation at risk.

“This should worry us all primarily because of what it says about the visibility we will have into the next outbreak,” Walensky told the Senate health committee. “We will be back to square one having to build and negotiate surveillance capacity while we fight a pathogen.”

While public health experts agree the U.S. has many more tools to fight Covid today, they warn the virus will remain a persistent threat to the elderly, the vulnerable and the nation’s fragmented, battered health-care system.

“I think we’ve passed the worst now, but there’s going to be a steady drumbeat of hospitalizations and deaths for many years to come,” said Lawrence Gostin, director of the O’Neill Institute for National and Global Health Law at Georgetown University.

The virus was the fourth-leading cause of death in the U.S. in 2022 – two years after Covid first emerged – behind only heart disease, cancer and unintentional injuries.

The World Health Organization declared an end to the global Covid emergency on Friday. But WHO chief Tedros Adhanom Ghebreyesus warned national governments against dismantling the systems they built to respond to the virus.

“This virus is here to stay. It is still killing, and it’s still changing. The risk remains of new variants emerging that cause new surges in cases and deaths,” Tedros said.

More than 1,000 people are still dying a week from Covid in the U.S., the overwhelming majority of whom are age 75 or older, as the public has largely lost interest in staying up to date on vaccines.

Only 42% of seniors are up to date on their Covid vaccines, according to CDC data. Just 17% of the total U.S. population has gotten the latest booster.

“You need to remain up to date to have adequate protection,” said Dr. James Lawler, infectious disease expert at the University of Nebraska Medical Center.

“Similar to immunity from vaccination, surviving Covid gives you immunity, but that immunity doesn’t last,” Lawler said.

The Biden administration says the end of the emergency will not impact access to Covid vaccines and antiviral treatments, because there’s still a federal stockpile, but many consumers will have to start paying for Covid tests.

Gostin said a misinformation campaign against vaccines, particularly in conservative states, as well as a general vaccine fatigue has put the nation’s health at risk.

Meanwhile, millions of people are at risk of losing coverage through Medicaid, the public health insurance program for lower-income people, as states are now allowed to review eligibility for the first time in years. Congress basically banned states from kicking people off Medicaid during the pandemic, but these protections expired in April.

“We’re going to see the unravelling of the social and health-care safety net over the next months,” Gostin said. “There will be a surge in uninsurance and people lacking access to health care,” he said.

Leading medical associations warned the Biden administration last fall that emergency departments were at a breaking point with patients forced to wait due to inadequate bed capacity and staffing.

And hospitals now face the persistent threat of Covid on top of disease from flu and and respiratory syncytial virus, which already strained capacity during bad respiratory virus seasons prior to the pandemic.

“We have really lost so much health-care capacity in this country by loss of beds, loss of health-care workers,” said Michael Osterholm, a leading epidemiologist and director of the Center for Infectious Disease Research and Policy in Minnesota.

“We better hope we’re not going to see a big surge in infectious disease cases of any kind in the months to years ahead,” Osterholm said.

Lawler, who advised the Bush and Obama administrations on biodefense and pandemic preparedness, said hospitals may need the flexibilities provided by the public health emergency if there are major Covid surges again in the future.

“I am not optimistic that once the public health emergency declaration goes away, that anybody in Washington is going to be eager to declare another, even if it’s warranted,” he said.