Do COVID vaccines work in people with HIV, cancer or organ transplants? What we know

COVID-19 vaccines do a remarkable job in protecting people from severe disease, but some evidence shows people with weakened immune systems may not develop as robust antibody responses — or any at all.

Immunocompromised people were largely left out of initial clinical trials for the shots, so little is known about how effective the vaccines are in the group.

But two new studies published this month suggest people with some conditions such as HIV and solid tumor cancers develop sufficient antibodies against the coronavirus, while others like those with organ transplants or blood cancers are less likely to respond to the vaccines.

Some people, particularly those receiving treatments for their conditions, developed muted antibody responses compared to others. But doctors aren’t sure how that translates to protection against COVID-19.

The added evidence offers both good and cautionary news, but the researchers say people with weakened immune systems should continue to act as if they aren’t protected from COVID-19, regardless of whether they have detectable antibodies or not.

Preventive measures such as wearing masks, washing your hands and physical distancing are even more important following the Centers for Disease Control and Prevention’s recent update that says vaccinated people can safely ditch their masks in most settings.

“At this point, clinical advice does not change for immunocompromised people, whether an antibody test is positive or negative,” lead author of one of the studies, Dr. Ghady Haidar, a transplant infectious diseases physician at the University of Pittsburgh Medical Center, said in a statement. “A positive antibody test does not give us certainty that they are protected against the virus, and the risk of COVID-19 causing serious complications and death still exists.”

Haidar’s team tested blood samples from 489 immunocompromised patients, including those with organ transplants, autoimmune disorders, blood cancer, solid tumor cancer or HIV, and 107 healthy health care workers who were fully vaccinated between April and June.

Of the healthy group, 98% produced antibodies after vaccination, while only 37% of organ transplant patients, 55% of blood cancer patients, 82% of solid tumor cancer patients, and 84% of those with autoimmune disorders developed the protective proteins.

Strikingly, about 95% of people with HIV developed antibodies after getting their shots, according to the pre-print study posted online Wednesday.

People who received their organ transplant less than a year ago were less likely to respond to vaccination. Among transplant patients, those who received new lungs had the poorest immune response (22%), while people who got new livers developed the best (60%).

People receiving treatment less likely to respond to COVID-19 vaccines

Joining the list of those less likely to produce antibodies after vaccination are cancer patients receiving radiation therapy and those taking certain medications, such as “antimetabolites for transplant and anti-CD20 monoclonal antibodies for autoimmune disorders.”

A separate study published June 18 also found that patients taking Rituximab, a medication used to treat blood cancers and autoimmune diseases, within six months of vaccination developed no antibodies. The University of Texas researchers also learned those on chemotherapy produced a muted response compared to the general population.

“How that relates to protection against COVID-19, we don’t know yet,” study co-author Dr. Dimpy Shah, a researcher with the UT Health San Antonio MD Anderson Cancer Center, said in a statement.

Among the 131 patients with cancer in the study, 94% produced antibodies three to four weeks after full vaccination, most of which had solid cancers as opposed to cancers in the blood.

“We could not find any antibodies against the virus in those patients,” Shah said. “That has implications for the future. Should we provide a third dose of vaccine after cancer therapy has completed in certain high-risk patients?”

A handful of other studies have similar findings.

A study of 436 transplant patients across the U.S. found that only 17%, or 76 people, developed COVID-19 antibodies three weeks after receiving the Pfizer or Moderna vaccine.

Another paper on about 1,200 patients with Crohn’s disease or ulcerative colitis in the U.K. who were taking treatments for their conditions found that just 34% built an immune response to the Pfizer vaccine and 27% after the single-dose AstraZeneca shot, which is not authorized in the U.S.

Other parts of immune system can also protect you from COVID-19

There are several elements of the immune system that play a role in protection from viruses aside from antibodies, which naturally decline over time no matter the illness.

B cells and T cells, for example, are immune cells that communicate with each other to kick start a chain reaction of responses when exposed to a virus or bacterium. There are also “memory B cells” that can remember if you’ve been infected with or vaccinated against a pathogen.

Neither of the studies tested for these responses, so it’s still possible immunocompromised people can fight off the coronavirus in the absence of antibodies.

Researchers haven’t tested whether people with weakened immune systems are more likely to get infected with the coronavirus after vaccination, but “I think common sense says yes,” Haidar told McClatchy News in April.

Such cases are called “breakthrough infections,” which includes those that occur two weeks or more after completing COVID-19 vaccination. About 4,115 cases have been reported in the U.S. as of June 21, mostly among those older than 60; 750 of them have died.

The CDC says it hasn’t found any “unexpected patterns” tied to patient demographics or specific vaccines among the reported cases.