Covid vaccination protects against severe kidney damage, study suggests
Complications from a Covid infection can harm the heart, brain, lungs and kidneys. A new study finds that patients hospitalized for Covid were less likely to suffer severe kidney damage if they were vaccinated.
Researchers at UCLA Health analyzed electronic medical records at a large academic hospital between March 1, 2020, and March 30, 2022, of approximately 3,500 hospitalized patients, ages 18 and older, and compared hospitalized patients who got at least two primary doses of the Moderna or Pfizer mRNA vaccine or one dose of Johnson & Johnson Janssen vaccine for Covid with hospitalized patients who had not been vaccinated.
The researchers examined which participants developed kidney disease severe enough to require a type of dialysis known as CRRT, or continuous renal replacement therapy. The nonstop dialysis therapy does the work of the kidneys by filtering and removing waste from the blood. It’s typically used when a patient is in intensive care, said lead author Dr. Niloofar Nobakht, health sciences clinical associate professor of medicine in nephrology at UCLA Health.
The study found that 16% of unvaccinated patients with Covid were more likely to need CRRT, compared with 11% of vaccinated patients during their hospital admission. Unvaccinated patients were more than two-and-a-half times as likely to need CRRT after leaving the hospital — and also had a much higher risk of dying after being discharged, compared with vaccinated patients.
In a 2021 study, researchers at Yale University School of Medicine found that among hospitalized patients with Covid, approximately 30% develop acute kidney injury — an abrupt, usually reversible form of kidney dysfunction. Patients hospitalized with Covid were twice as likely to need dialysis than patients hospitalized for other reasons.
There is a major limitation in the new study. The researchers did not have the full data on baseline kidney status for the patients —meaning, it’s not known how well their kidneys were functioning before the infection — so the benefits of the vaccine may be overestimated or underestimated, said Dr. Scott Roberts, associate medical director of infection prevention at Yale School of Medicine, who was not part of the new study.
How Covid can damage the kidneys
Covid can injure the kidneys either directly or by damaging other organs such as the heart and lungs, Roberts said. The more severe the symptoms, the greater the risk.
“Conversely, mild or asymptomatic infections rarely cause significant kidney harm,” said Yong Chen, a professor of biostatistics and director of the Center for Health AI and Synthesis of Evidence at the University of Pennsylvania, who was not associated with the new study. Chen researches Covid complications, including kidney problems, in children and adolescents.
The risk of post-Covid kidney complications is especially high in older people or the immunocompromised, but it’s likely connected to the severity of the initial infection, rather than the virus itself, experts say.
“Comparing Covid to people hospitalized with flu, for example, shows that both have an elevated risk of kidney injury, and it seems to track with how sick they were during their hospitalization,” said Dr. F. Perry Wilson, associate professor of medicine and public health at Yale University School of Medicine who has studied kidney injury in Covid patients. “Among people with Covid, I would expect that, all else being equal, the vaccinated group just has less severe disease and thus less kidney trouble.”
Why vaccination may protect the kidneys
“Vaccination protects kidneys mainly by preventing the severe forms of Covid that cause kidney injury,” Chen said. “While vaccines don’t directly shield kidney cells, they blunt the systemic illness that otherwise leads to multi-organ failure.”
However, both Covid infection and the vaccines may be risky for people with glomerulonephritis, a type of kidney disease where the filtering units known as glomeruli get damaged
Dr. Jeffrey S. Berns, clinical nephrologist and professor of medicine and pediatrics at the Hospital of the University of Pennsylvania, said there are reports of adults and children with glomerulonephritis having a relapse of the condition or developing the condition for the first time following Covid infection and also vaccination. Berns was not part of the study.
Risks for children
The study only applied to people 18 and older, but experts say children with Covid can get acute kidney injury and some of them may have permanent kidney damage.
“In a study led by our team, the results also showed that children with prior Covid had a 35% higher risk of new-onset chronic kidney disease over six months,” Chen said.
In late May, Health and Human Services Secretary Robert F. Kennedy Jr. said the Centers for Disease Control and Prevention will no longer recommend routine Covid shots for healthy children and pregnant women. Doctors say it’s too soon to know whether the revised guidelines would contribute to unvaccinated children’s increased risk of kidney injury.
Even as a new variant of the Covid virus is gaining momentum in the United States, there are fewer cases of acute kidney injury associated with the illness than in the early years of the pandemic.
“As more and more people got vaccinated and or had some degree of immunity from prior infection, disease severity was not as bad and AKI became much less common,” Berns said.