CHICAGO >> Even though she is fully vaccinated, Barbara Creed can’t yet visit her grandchildren in Texas.

Creed is among thousands for whom the vaccine is less effective because she has received an organ transplant. The 67-year-old Oak Park, Ill., resident has watched the state reopen with some trepidation, as mask mandates for the unvaccinated are on an honor system and the delta variant is fueling an upswing in infections in Illinois.

People such as Creed with compromised immune systems have relied on others to be vaccinated for full protection against the virus. But the country’s march toward herd immunity has been stymied by vaccine hesitancy, which still flourishes in some communities.

The Food and Drug Administration has approved a third dose of the newly approved Pfizer vaccine, and given an emergency authorization for a third dose of the Moderna vaccine, for immunocompromised people 12 and older.

Experts say immunocompromised people need the additional shot because their immune systems don’t respond as well to initial doses of the vaccine as healthy people, and the response they do have wears off over time. As such, their third shot is not regarded as a booster.

Immunocompromised people account for about 2.7% of U.S. adults, according to the Centers for Disease Control and Prevention.

Until Creed gets that third vaccine, she is safest living with restrictions that others who are vaccinated are no longer facing.

She has taken many precautions: wearing masks in public, social distancing and socializing only with small groups of people who are vaccinated. She also abstained from travel.

Transplant patients take drugs to suppress their immune system so their body doesn’t reject the donated organ. Creed, a retired music teacher, received a double lung transplant last year.

The vaccine — while extremely effective for most people — likely offers some protection to transplant patients. But this group is still more vulnerable to contracting the disease and becoming hospitalized, said Dr. Daniel Dilling, professor of medicine at the Loyola University Stritch School of Medicine and medical director of the hospital’s lung transplant program.

Transplant patients want people to know that it is important for healthy people to get the vaccine to protect those who have compromised immune systems.

“It’s an act of patriotism to get the vaccine for the sake of our fellow citizens, to collectively do what we can as a community to fight this virus together,” Dilling said.

Organ transplant patients weren’t studied in the original vaccine trials, but Illinois resident Monica Fox is participating in a study by Johns Hopkins on the vaccine’s effectiveness in transplant patients.

Fox, who received a kidney transplant in 2016, got the vaccine and has periodically been tested for COVID- 19 antibodies. So far, the tests have not found them.

“I was disappointed, but I was glad to know so I didn’t have a false sense of total security,” Fox said.

Antibody tests offer some data but are an imperfect measure of a person’s level of protection against the virus. Dilling said cells that can fight infections, called T cells, could offer protection against the virus, even if people do not develop antibodies. T-cell response is not something measured in most labs, he said.

But some organ transplant patients are becoming reinfected, sometimes becoming ill enough to be hospitalized, Dilling said. That, coupled with the fact that some patients do not appear to have developed antibodies, illustrates their weakened level of protection.

And even in cases when a transplant patient has developed some antibodies, the advice is to continue masking and take other precautions, Dilling said.

Mark Lakoduk, a lung transplant recipient, stopped making food deliveries when the pandemic hit. And he stopped kissing his wife.

“We were so worried about it,” he said. “Before COVID we would kiss each other good night every night.”

Lakoduk has resumed food deliveries and other activities, especially because he contracted COVID-19 in January and recovered from it. And he has continued kissing his wife good night.

But the return to normalcy creates anxiety in some transplant recipients. It’s hard to know who might be a threat to their safety.

“People who don’t want to get vaccinated also don’t want to wear masks,” Fox said.

Fox went to get her nails done recently. She wore a mask, even though the salon did not require it. She also spends time with vaccinated family members.

But she worries about vaccine skepticism. Fox is director of outreach and government relations at the National Kidney Foundation of Illinois and is working on programming to increase vaccinations.

“People need good information,” she said. “I know we are tired of lockdowns. I know we are tired of wearing masks, but consider that there is a substantial population of people who are still at risk.”