The discrepancy for seniors is likely due to changes in the way the federal government has distributed vaccines, said David Grabowski, a professor of health care policy at Harvard Medical School. Although the Biden administration coordinated vaccine delivery to nursing homes, football stadiums and other targeted venues early last year, the federal government has played a far less central role in delivering boosters, Grabowski noted.

Today, nursing homes are largely responsible for boosting their residents, relying on pharmacies they traditionally hire to administer flu shots, Grabowski said. And outside of nursing homes, people generally must find their own boosters, either through clinics, local pharmacies, or primary care providers.

Dr. Thomas Frieden, a former CDC director, said that, in theory, shifting responsibility for ongoing Covid immunization from government-sponsored clinics to individual providers might seem logical, given the privatized design of U.S. health care. In reality, Frieden said, that approach is not working because “our primary health care system is life-threateningly anemic” and not set up to readily take on a public health mission.

Most health care providers don’t have the technology to securely track which patients have been vaccinated and schedule follow-up shots, Frieden said. Nor are there financial incentives for doctors to get their patients vaccinated and boosted.

Even before the pandemic, 28 percent of Americans didn’t have a regular source of medical care.

Grabowski said nursing homes in particular need more support. Although fewer than 1 percent of Americans live in nursing homes or assisted living facilities, they represent more than 20 percent of Covid deaths. He would like the Biden administration to resume coordinating booster delivery at nursing homes through mass vaccination efforts. “I would have these centralized clinics go back to get residents and staff boosted all at once,” Grabowski said. “That strikes me as a no-brainer.”

The Biden administration has touted its continuing efforts to vaccinate older people. For example, the Centers for Medicare & Medicaid Services has sent quality improvement teams to advise nursing homes with low vaccination rates. The Medicare program has mailed letters to all 63 million beneficiaries to encourage them to get boosters and has sent millions of emails and text message reminders.

Still, many health advocates agree that the country has lost the momentum it had during the first months of the Covid vaccination campaign.

“There doesn’t seem to be the urgency that we saw with the initial shots,” said Lori Smetanka, executive director of the National Consumer Voice for Quality Long-Term Care, an advocacy group.

Some researchers attributed the slowdown to the initial disagreement among health leaders over the value of boosters, followed by a staggered rollout. Boosters were approved in stages for different age groups, without the fanfare that typically comes with a single major policy change. The CDC recommended booster shots for people with weakened immune systems in August; then for older people in October; for all adults in November; and for kids 12 and up in January.

In addition, although advertisements for vaccines seemed to be everywhere a year ago, government agencies have been less vocal about encouraging boosters.

“I felt like we were all getting hit over the head originally and all roads led to vaccines,” Grabowski said. “Now, you have to find your own way.”

For many older people, the barriers that can make private health care difficult to access in nonpandemic times also exist for boosters. For example, many seniors prefer to walk in to receive a vaccination, without an appointment, or to make appointments by phone, even as pharmacies increasingly turn to online-only scheduling that requires customers to navigate a multilayered system. Some seniors also lack ready transportation, a sometimes-towering obstacle in rural areas where health clinics can be 20 to 30 miles apart.

“If people have to take two buses or take time off from work or caregiving for their family, people are less likely to be vaccinated,” Smetanka said.

Dr. LaTasha Perkins, a family physician in Washington, D.C., said she has worked hard to persuade her family in Mississippi to get vaccinated. Her grandmother agreed to get her first shots in the fall, just as the CDC approved boosters for all adults.

“We finally got to a place where we got people to get two shots, and then we said, ‘Oh, by the way, you need a third one,’” said Perkins. “That was jarring for a lot of communities. They would say, ‘You convinced me to buy in, and now you’re saying that two shots aren’t good enough.’”

Although national leadership is important, Perkins said, local connections can be more powerful. Perkins has given talks about vaccines at her church. Congregants are more likely to trust her medical advice, she said, because she’s a tithing member whom they see every Sunday.

Some communities have done a better job of overcoming reluctance than others. Minnesota has boosted 83 percent of vaccinated residents ages 65 and older, a larger share than in any other state, according to the CDC.

Minnesota’s Dakota County has boosted a greater percentage of vaccinated people 65 and older than any other U.S. county with at least 50,000 seniors, according to a KHN analysis of CDC data.

Christine Lees, an epidemiologist and public health supervisor for Dakota County, said her department hired an agency to provide booster shots to residents and staffers in nursing homes and assisted living facilities. The health department runs vaccine clinics at lunchtime and some evenings to accommodate working people.

The department drew on money from the federal Coronavirus Aid, Relief, and Economic Security, or CARES, Act to purchase a mobile vaccine clinic to bring boosters into neighborhoods and mobile home parks. “We ran it all last summer, and we’ve started it back up again,” Lees said. “We went to food shelters and libraries. We went out at least once a week to keep those numbers high.”

Community health workers paved the way for vaccine clinics by visiting residents in advance and answering questions, Lees said.

Dakota County also used funds from the American Rescue Plan Act to provide $50 incentives to people receiving initial vaccines and boosters, Lees said. The incentives “were really important for people who might have to pay a little extra to travel to a vaccine site,” Lees said.

Topol, at Scripps, said it’s not too late for federal leaders to look at what’s working — and not — and to relaunch the booster effort.   

“It will be hard to reboot now. But an aggressive, all-out campaign for seniors — whatever it takes — is certainly indicated,” Topol said. “These people are the sitting ducks.”