Several recent studies have linked additional health problems with what is called "long COVID."

Long COVID describes a condition in which symptoms of the coronavirus infection remain for a long time. The findings in the studies were recently released and have not yet been fully reviewed or supported by other research. Reuters news agency reported on the findings.

COVID-19's effects on the kidneys

One study, for example, has found a link between ‘long COVID' and kidney problems.

The researchers examined the health records of more than 1.7 million U.S. veterans. That includes nearly 90,000 patients who had COVID-19 infections and had symptoms lasting at least 30 days.

The researchers found that those people were at higher risk for new kidney problems compared to those who had not been infected. This was true even when the people had not been hospitalized. Severe infections resulted in poorer kidney health, the researchers reported. The study was published recently in the Journal of the American Society of Nephrology.

About five percent of the long COVID group developed at least a 30 percent drop in an important measure of kidney function known as eGFR. People with long COVID were 25 percent more likely than uninfected people to have a 30 percent decrease in eGFR. Higher risks were reported in those with more severe COVID-19 cases.

The researchers noted that, as people age, their kidneys often do not work as well. Dr. Ziyad Al-Aly of Washington University in St. Louis helped write the study. He said damage to the patients' kidneys was greater than what happens with normal aging.

Changes in the sense of smell

Another study found that loss of smell may be followed by changes in the ability to smell after a COVID infection.

Many people who report losing their sense of smell because of COVID-19 do regain it. But a recent study found that some patients later report smell distortions and unexplained smells.

A group of international scientists published their findings in medRxiv. The service publishes early medical research before it is fully reviewed.

The researchers examined responses from 1,468 individuals who had COVID-19 between April and September 2020. All had suffered a loss of smell and taste at the start of their sicknesses.

Early on, about 10 percent also reported smell distortions and unexplained smells. At six to seven months after first reporting a loss of smell, 60 percent of women and 48 percent of men had regained less than 80 percent of their pre-sickness ability to smell. And rates of smell distortions and unexplained smells had increased.

Nearly 40 percent reported smell distortions. They said, for example, "some things now smell like chemicals." About 25 percent reported unexplained smells. "Sometimes I can smell burning but no one else around me can," one person reported. Ongoing smell problems were seen more often in patients with more symptoms. The writers of the study suggested that problems with the sense of smell might be a central marker of long COVID.

Antibodies in weakened patients

A third study found that one kind of COVID-19 vaccine can produce antibodies even when a person has a weakened immune system. The researchers said mRNA COVID-19 vaccines cause protective immune reactions in most cancer patients with solid cancer growths. They also produce antibodies in people taking medicines that cause their immune systems to weaken. That is what two recent studies in Israel suggest.

The researchers found that six months after the second shot of the vaccine from Pfizer/BioNTech, 79 percent of 154 patients with solid cancer growths had developed antibodies. The Pfizer vaccine is an mRNA vaccine, one that uses changed genetic material.

At the same time, 84 percent of 135 people without cancer developed antibodies. Antibody levels were similar in the two groups, the researchers reported recently in the publication Cancer Discovery.

Separately, U.S. researchers studied 133 adults taking medicines that cause a weakened immune system and 53 healthy volunteers. The study found that, three weeks after the second shot of a vaccine from Pfizer/BioNTech or Moderna, nearly 90 percent of the immune-weakened people had developed antibodies. But many had lower reactions compared to the healthy group. The study was published in Annals of Internal Medicine.

Both studies involved a small number of people.

Getting better outside the hospital

And finally a separate study on the antibody treatment from Regeneron found a lower rate of hospitalization in patients.

People with COVID-19 treated with a monoclonal antibody mixture had lower hospitalization rates than those without the treatment, a study recently said. The patients had mild to moderate COVID-19 cases. The researchers reported the findings in EClinicalMedicine. The study was not randomized and cannot prove the treatment caused the better results. But it suggests high-risk patients with mild or moderate COVID-19 may be able to recover without having to go to the hospital.

I'm Caty Weaver. And I'm Alice Bryant.

Reuters news agency reported this story. Alice Bryant adapted it for VOA Learning English. Mario Ritter, Jr. was the editor.

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symptom –n. a change in the body or mind that shows that a disease is present

function –n. the purpose or activity that something does or is used for

in excess –phrase more than

distortion –n. a change in something so that it is no longer true, normal or believable

immune system –n. the system that protects the body from disease and infection

randomize –v. to do in a way that shows no plan or system