Some people are getting a 3rd Covid shot. Getting it too soon could backfire, Fauci says.

Kris Fredrick, an engineer at a television station in Amarillo, Texas, felt relieved when he got a second dose of the Moderna vaccine Feb. 1. But when the delta variant of the coronavirus started to spread across the U.S., Fredrick became unsettled.

He has diabetes and hypertension, so he was worried he remained vulnerable to serious illness. He was concerned about the “anti-vaccine and anti-science sentiment” in his town, and he grew even more alarmed when he learned that two local hospitals were purportedly not requiring their employees to get vaccinated.

That’s why Fredrick, 35, decided to get a third dose of Moderna last Tuesday. He made an appointment at a local CVS pharmacy, asked for a “booster” shot and walked out of the building with what he felt was a stronger shield against a variant that has become the dominant strain of coronavirus in the country.

The top U.S. public health officials announced this week that all Americans can get a booster shot starting the third week of September. The federal guidance says adults over the age of 18 will be eligible for another dose of Pfizer or Moderna eight months after their second dose.

But there is a cohort of people across the U.S. who do not want to put off a booster shot as the delta variant rages and “normal life” still seems remote. In some cases, people are jumping the gun so they can participate in regular life activities; in other cases, people with weak immune systems are eager for a feeling of increased safety.

Fredrick knows he got his third dose before the eight-month window closed — in his case, roughly two months ahead of the federally recommended schedule — but he has few regrets about circumventing federal recommendations.

“I’m around people in town who don’t want to wear masks or ignore Covid, so I felt I needed to be as protected as I could around here,” Fredrick said in a phone interview this week.

He said nobody at the pharmacy tried to prevent him from getting a third dose.

Howard Miller, a retired university professor who lives in the suburbs of Minneapolis, got his second vaccine dose in February. He was “thrilled” at the time, and he didn’t experience any adverse reactions. He believes he will be eligible for a booster shot sometime in October under the new federal guidelines.

But as the delta variant surges across Minnesota, Miller, 68, is weighing his options: Does he wait the full eight months or get another shot as soon as he can?

At the moment, he said, he is leaning toward the second option.

“I would check with my primary care physician, but I’d certainly be inclined,” Miller said, adding that he is concerned about his risk factors, such as a history of heart disease and diabetes. “If the physician says, ‘No worries,’ I’d do it.”

He is also eager for an extra layer of protection that might allow him to dive back into some of his favorite hobbies, including going to concerts and restaurants with his girlfriend.

The Centers for Disease Control and Prevention has said people who are severely vulnerable or immunocompromised — including solid organ transplant patients, people with advanced HIV and certain cancer patients — should try to get a booster shot as soon as they can.

But for people without severe immunocompromising conditions, getting a third dose soon after a second might actually be counterproductive, according to some public health experts.

In an interview with MSNBC’s Andrea Mitchell this week, Dr. Anthony Fauci said people would be wise to give their immune systems a chance to “mature” before rushing to get a booster.

“I think that might defeat the purpose, and that’s the reason why we landed at eight months,” Fauci said, adding that the U.S. government could only recommend an eight-month period and otherwise leave personal decisions in the hands of the general population.

Deepta Bhattacharya, professor of immunobiology at the University of Arizona, echoed Fauci’s comments, telling NBC News that getting a booster soon after a second shot “raises the possibility that it won’t work that well.”

He explained that third doses will likely work much better after fully vaccinated people lose some of the antibodies in their systems. He was quick to add that people will need to balance that likelihood “against the risk that your protection is reduced during the interval between shots.”

The decision to cut the proverbial line raises various ethical questions, too — especially as public health authorities around the world sound the alarm about shortages in poor and developing nations.

World Health Organization officials and doctors have forcefully pushed back against the Biden administration plan, saying it is “immoral” and “unconscionable” to start handing out boosters to folks in the U.S. before people in less privileged countries even have access to a first dose.

"We're planning to hand out extra life jackets to people who already have life jackets, while we're leaving other people to drown without a single life jacket," Dr. Michael Ryan, the emergencies chief at WHO, told reporters.

Of course, many people in the U.S. say they plan to abide by the federal guidelines.

Shauna Baker, of Greeley, Colorado, said she plans to wait to seek out a booster shot until she becomes technically eligible in December.

That’s not because Baker’s family is somehow immune to worrying about delta. She is the primary caregiver to her 82-year-old father, who deals with several comorbidities and just went through what she described as a “year from hell.”

Baker’s father is currently hospitalized with his fourth septic infection. Baker, for her part, lives with asthma.

“We can’t afford for me to get sick,” she said. “We can’t afford for him to get sick because it’s probably going to kill him.”

Yet Baker, 55, said she is resolved to stay in her place in line behind people with more severely compromised immune systems, placing her trust in the expert guidance of federal health officials.

“My No. 1 job is to keep him protected,” she said, “and I will do everything that I can as soon as possible after that.”

Aaliyah Miller, 43, said while she supports people with compromised immune systems getting booster shots as soon as possible, she would personally “like to see more people get [first and second doses], before we start giving healthy individuals like myself the booster shot.”

Miller, the mother of 5-year-old twins in Connecticut, is fully vaccinated and will become eligible to receive a booster around the end of January.

She said the U.S. still has work to do in convincing skeptical people to get their first vaccinations and fight misinformation.

“I feel very lucky here in the U.S., and we don't appreciate it — well, some of us don't,” she said. “We also need to get more people vaccinated around the world, so we can hopefully be able to mitigate this.”

Fredrick, the TV station engineer, seemed to agree with the WHO and other critics of the U.S. strategy, saying he believed the stark imbalances in global vaccine supply were “not fair at all.”

“It’s obviously hypocritical, because I did get it, but I think we should be doing all we can to help other countries. The pandemic is worldwide, and it’s not going to be over until it’s over everywhere,” he said. “We should be shipping doses to countries that need them the most.”

He said he was not especially concerned with the possibility that his booster might be less effective than one he could have gotten starting late next month, explaining that his physician essentially advised him to get a booster as soon as he could.

“I didn’t think it through as much as I should have, probably,” Fredrick said. “I probably should have waited. But as soon as I saw it was a thing I could do, I did it.”