On some days Marilyn Datillo, a vaccine nurse, used to see 900 people enter Mercy Covid Vaccine Clinic in Kirkwood, a St Louis suburb. Now, she said sometimes fewer than 20 people visit the clinic in one day – even though only 55% of Missouri residents are fully vaccinated and just 22% are boosted.

When someone does show up to get vaccinated, “you celebrate”, Datillo said.

But she and infectious disease doctors do not anticipate many more people suddenly deciding to get their first shot – or ending delays on second shots and boosters – amid declining numbers of Covid cases and hospitalizations in the US; the lifting of vaccine mandates and other restrictions; and some talk of the end of the pandemic being in view.

The number of new people getting vaccinated in America has steadily declined in recent months, according to Centers for Disease Control and Prevention (CDC) data. The seven-day average of new vaccinations now mirrors the rates from December 2020, when there was a limited supply of the vaccines.

But doctors emphasize that the virus remains a threat in the US and that people who are not vaccinated are at greater risk of become severely ill or dying. They point to the fact that the seven-day average of new cases on 23 February in the United States was 76,667, according to the New York Times data. On 23 February last year, the seven-day average was 67,854.

The seven-day average of deaths on those dates were also not much different: 1,908 and 2,056.

“I can think back to just last week when I had to put someone on a breathing machine who was unvaccinated, so this continues to be with us,” said Dr Anuj Mehta, a pulmonologist with Denver Health in Colorado, where 69% of people are fully vaccinated and 34% boosted.

Even though the number of cases and hospitalizations have plummeted since the height of the Omicron surge, Mehta continues to worry because new variants will emerge “until we get the entire world vaccinated”, he said.

“I could imagine a time this summer or fall” when people who “tested positive for Covid in the last three months will think that they have ongoing immunity, and I think that’s not true”, said Mehta.

But Mehta admits that he is unsure whether it’s realistic that the whole world will get vaccinated.

He said he is encouraged by the development of a new Covid vaccine that does not need to be stored at as low temperature as existing ones and thus could make it easier to vaccinate much of the world.

“We need to push forward on that and help as a global community member to achieve that goal, which in turn will help protect the United States,” said Mehta.

Dr Farrin Manian, an infectious disease specialist and chair of the department of medicine at Mercy Hospital St Louis, conceded that there are people who aren’t going to change their minds about vaccination. But in talking with patients, he still encounters some who are open to it.

“I think we just need to talk about what has happened in the last year and hopefully get people to change their minds and honestly discuss the effectiveness of the vaccine in reducing hospitalizations,” said Manian.

Mehta also thinks there could be more opportunities for conversations about the vaccines because so many people skipped primary care during the pandemic and will hopefully now return to see their doctors.

A January poll from the University of Michigan Institute for Healthcare Policy and Innovation found that among older adults, only about half of the unvaccinated had rescheduled a primary care appointment that was disrupted by the pandemic in 2021, compared with 85% of those who were boosted and 74% of those who were vaccinated.

“We would have a slight increase in the rates of boosting and vaccines in general if people were to have a real conversation with an individual provider,” said Mehta. “Seeing patients in the clinic with lung disease, I am far more likely to convince somebody to get the vaccine when I am talking to them in person.”

“When I ask them why they don’t want to, they cite everything they see on Facebook, and I am able to counter that in an individual appointment, when they are there to check in on their asthma or their COPD,” he added.

Datillo, the vaccine nurse, still encounters people who decided to get vaccinated only after losing a loved one who also wasn’t vaccinated.

And people who didn’t get a vaccine because they were concerned about its impact on their ability to have children.

Or people who initially didn’t get a booster because, they said, “I got Covid anyway, and I was sick, so why bother getting the booster?”

Datillo is, of course, only seeing them because they eventually decided to get the shot, but most people’s “judgement has been made”, she said.

If that’s the case, people who have not gotten a booster or people whose immunity from an infection has waned could “become more susceptible to severe disease”, said Bill Hanage, an epidemiologist at the Harvard TH Chan School of Public Health. “I do think it’s of the utmost importance that we keep an eye on the virus over the summer and don’t assume that everything that’s going to happen is in the rearview mirror.”