Christy Foreman pulled out of the drive-through coronavirus vaccination site in March, a jab of Johnson & Johnson in her arm, and breathed a sigh of relief.

A long year of hunkering down in her Baton Rouge apartment and ordering her groceries on Instacart was finally over. The 61-year-old, like the rest of the country, was ready for the slow return to normal. If cases kept falling, she’d even be able to go back to teaching in person at Louisiana State University in the fall.

Then came a drumbeat of reports showing the Johnson & Johnson shots might not offer the same level of immunity as other vaccines. Worried she might develop a breakthrough infection — or worse, face symptoms like brain fog — Foreman decided she needed an extra shot. She’d have to lie to do it. But other countries were already giving boosters, while U.S. health officials seemed to be waffling on the issue, she said. It was worth the risk.

“We’re being left to make our own decisions,” Foreman said. “We were told at the beginning not to wear masks and not to buy masks because they wanted to save them for health-care workers. Then they had to backtrack, which caused all sorts of confusion. It’s sort of the same thing.”

Across the country, vaccinated Americans have sought out extra shots because they fear their current doses aren’t enough to ward off a virus once again raging in all 50 states. It’s not clear how many have taken matters into their own hands. For Pfizer and Moderna recipients alone, the Centers for Disease Control and Prevention estimates that 1.1 million have received additional shots, according to an internal document reported Wednesday by ABC News.

The trend reflects broad public confusion about the protection offered by the vaccines at a critical time in the nation’s pandemic response, with the hyper-transmissible delta variant causing infections and hospitalizations to soar.

Frustrated by what they consider murky guidance from health authorities, people have received third or even fourth immunizations from local pharmacies and vaccination sites, where their previous appointments haven’t caught the attention of health workers. Some say they’ve bucked advice from their own doctors, turning instead to Google for information on whether the extra shots are worthwhile.

“The chaos is, in part, due to lack of guidance and trust,” Eric Topol, director of the Scripps Research Translational Institute, said in an email. “I hope there will be full transparency and a plan/timeline for the public to address these concerns.”

People are seeking out extra vaccines — a phenomenon Topol dubbed “booster-mania” — even as the government is moving to make additional shots available to some vulnerable individuals.

The Food and Drug Administration is expected as soon as Thursday to clear the way for extra doses of vaccines for people with compromised immune systems. An advisory committee to the Centers for Disease Control and Prevention is planning to meet Friday to consider any FDA action — and is likely to recommend that the immunocompromised talk to their doctors about getting the shots. Federal health officials have said about 3 percent of U.S. adults are immunocompromised.

Meantime, the FDA over the next several weeks will be scrutinizing data and weighing whether to authorize booster shots for other groups, including older people, health-care workers and residents of nursing homes.

In addition, by the end of this summer, the FDA is expected to fully approve the Pfizer-BioNTech vaccine. That means that doctors will be able to give additional vaccine shots to anyone they choose, regardless of whether the FDA has specifically authorized it.

Questions about the strength of the Johnson & Johnson vaccine were enough to convince some to seek out one of the mRNA-based shots. The single-shot regimen remains highly effective in slowing transmission and preventing severe illness, but it isn’t as robust as the Pfizer or Moderna shots.

Roger Beatty, 68, received the Johnson & Johnson shot in March through his health-care conglomerate and soon had a nagging feeling he might need a booster. He devoured news articles and research to figure out the right course of action. He talked with his doctor, who was “studiously noncommittal” about the risks or benefits of an extra shot, he recalled. Ultimately, a news article that mentioned German Chancellor Angela Merkel’s decision to mix-and-match vaccines tipped the scales.

“I was looking for anybody who had any basis for saying ‘This is dangerous, don’t try this,’ ” said Beatty, a retired Silicon Valley high tech manager who lives in Boston’s suburbs. “I couldn’t find anything anywhere.”

In June, Beatty went to a local CVS for another jab. He said a clerk asked him if it was his “first or second” — a question he assumed referred to the Pfizer shot. First, he told her. “Five minutes later there was a needle in my arm,” he said.

Beatty said he never would have gone in had there been a vaccine shortage or a possibility of sending the doses to others in need. But the shots were more widely available than ever, and the threat of more dangerous variants weighed on him. “At my age,” he said, “I’m not going to mess around with this.”

For people with compromised immune systems, concerns about the efficacy of the vaccines are even starker.

Terry Deneen, who received a double lung transplant in 2016, got the Moderna shots in the spring after struggling to find an appointment. The 70-year-old from Chicago said he was just starting to enjoy a taste of normalcy — visiting family, going out to dinner with friends from his apartment building — when doctors warned him that the vaccines offered little protective value for many transplant patients. A covid-19 case could be lethal.

Deneen had read about how Israel had begun administering boosters to seniors and figured officials would soon do the same here. So he decided to “beat the rush” and seek another round, he said, even though his doctors equivocated about whether it was a wise decision. Last week he got another Moderna injection at a CVS. Workers there didn’t ask about his vaccine history, and he didn’t volunteer anything, he said.

Afterward, Deneen reflected on how lucky he was to have received transplant lungs that his body accepted. “It was like somebody had grown a set of lungs just for me,” he said. “I’m not going to throw it away by not getting a third shot.”

A CVS spokeswoman, Tara Burke, said the pharmacy chain doesn’t give additional vaccines to patients who say they’re already immunized.

“We’re following CDC guidance that the administration of a booster dose at this time is not recommended,” Burke said in an email. “So patients who have been fully vaccinated at a CVS Pharmacy, or who inform us that they were fully vaccinated by another provider, will not receive another vaccine.”

Janet Handal, 70, who got a kidney transplant a decade ago, said she got her first shot of the Moderna vaccine in January and her second in February. Antibody tests — administered as part of a Johns Hopkins study that is following the effectiveness of vaccines in the immunocompromised — showed she had almost no antibody response.

She decided on her own to get a Johnson & Johnson shot in late April. She went to a drugstore where she was not asked whether she had been vaccinated, she said.

Her antibodies shot up, but doctors told her the level is far below that of an “immunocompetent” person.

She plays it safe. “I don’t feel as at risk as I did before, but I mask everywhere I go,” she said. “I’ll go into a grocery store but I would not go to Macy’s and shop for two to three hours.”

Some of the people who have gotten a booster dose are clinicians who were in the first group prioritized to receive the vaccines.

One emergency room doctor in Kansas City, Mo., said he decided to get a third shot of Pfizer because of the recent spike in covid-19 cases in southwestern Missouri and because of two colleagues who became sick in recent weeks even though they were both fully vaccinated.

The 44-year-old doctor, who spoke on the condition of anonymity because he didn’t want to put the pharmacist or his hospital in jeopardy, said he received two doses of Pfizer in December.

He’s worried that the recent spike in cases is putting his health — and ability to treat patients — in jeopardy.

Late last year, every single hospital in the Kansas City area was “absolutely socked in,” he said in an interview. He works at Overland Park Regional Medical Center in Overland Park, a Kansas City suburb in Kansas.

“It was really a bad situation. Now we’re creeping back towards that. We’ve had multiple days in the last two weeks where the entire regional hospital network has gone on high volume status,” meaning no one can divert cases to another hospital and all are forced to stay open and accept patients, he said.

He suspects his level of immunity has declined since he got his shots in December — although research is not clear.

He said parts of Europe and Israel have been giving additional shots and their “quite good data” is showing “a little bit of decrease in immunization efficacy over six months.”

Two colleagues, both fully vaccinated and in their 30s and who are otherwise healthy, were sickened, he said. They weren’t sick enough to require visits to the hospital, but neither is back at work yet, he said. In the past several weeks, he has also seen four or five fully vaccinated elderly patients with underlying conditions — including a kidney transplant patient who also had COPD — be hospitalized for covid-19 illness.

When he made the decision, he went to a Walgreens in Kansas City. He told the pharmacist this was his first dose.

He has thought about the ethics of his action. “If there was a shortage of vaccines here and people were struggling to get them, I would have hesitated and not gotten a third shot,” he said. “But particularly here in rural parts of America, outside of Kansas City, in the red states, they have more vaccine than they know what to do with. We’re seeing a lot of vaccine expiring.”

He agrees that there needs to be a fairer global distribution system for vaccines, but that requires a centralized coordinated authority that has “some teeth,” something the World Health Organization is lacking, he said.

In the meantime, as an emergency room physician, “I got my hands all over covid secretions. I’m trying to keep myself safe to keep other people safe.”

In Baton Rouge, Christy Foreman, too, thought hard about whether her decision to mix-and-match vaccines would deprive someone else in need. Nothing she read convinced her that would be the case, she said. She went to an Albertson’s grocery store and got a dose of Pfizer to supplement her Johnson & Johnson injection. Her follow-up appointment is later this month, and she’s mulling whether to show up.

Foreman isn’t immunocompromised, but she worries about how her body would react to the virus. Her father’s struggles with brain fog have alarmed her since he fell ill with covid-19 last summer. She can’t risk symptoms like that interfering with her work as an English instructor, she said.

“I make my living using my brain. You can’t teach if you have that problem,” she said. “I just can’t afford that.”