FRIDAY, June 2, 2023 (HealthDay News) -- People unvaccinated for COVID-19 have significant odds of lingering illness if they get the virus, with one in six still suffering symptoms two years later, new research shows.

A study from Switzerland found that 17% of that group did not return to their previously normal health, and 18% reported COVID symptoms such as shortness of breath 24 months after their infection was gone.

“Persisting health issues create significant challenges for affected individuals and pose an important burden on population health and health care services,” lead researcher Tala Ballouz and colleagues wrote in the May 31 issue of the BMJ.

Ballouz, from the Epidemiology, Biostatistics and Prevention Institute at the University of Zurich, and her team called for clinical trials “to establish effective interventions to reduce the burden of post-COVID-19 condition.”

While most people who contract COVID-19 recover, others continue to have health issues that can affect quality of life and ability to work. This is termed long COVID.

Researchers have been unable to make firm conclusions about long-term treatment and support for these patients because previous studies have varied in their estimates of patient numbers and duration of symptoms.

For this study, the investigators looked at patterns of recovery and symptom persistence over two years in adults from the Zurich SARS-CoV-2 Cohort, an ongoing study of COVID-19 patients.

The study used data from more than 1,100 unvaccinated adults, average age 50, who had their infections confirmed between Aug. 6, 2020, and Jan. 19, 2021. Also included were 628 adults, average age 65, randomly selected from the general population who had not had the virus.

The study participants provided information on 23 potential long COVID symptoms at six, 12, 18 and 24 months after infection. The researchers also considered their age, sex, education, employment and pre-existing health problems.

More than half (55%) of participants reported returning to their normal health status less than a month after infection. Another 18% reported recovering within one to three months.

But almost one-quarter (23%) of participants reported that they had not yet recovered six months after infection. That was 19% at 12 months and 17% at 24 months.

And those still experiencing symptoms thought to be related to COVID-19 included 29% of participants at six months, 20% at 12 months and 18% at 24 months.

The COVID-19 group had excess risks for such symptoms as altered taste or smell (about 10%), malaise after exertion (about 9%), reduced concentration (roughly 8%), shortness of breath (almost 8%) and anxiety (4%) at month six compared to those who didn’t have COVID-19.

Patients who were older and had pre-existing health issues reported more or worsened symptoms, the study authors noted in a journal news release.

Study limitations include its reliance on self-reported health, which can be inaccurate.

Qiao Wu, a University of Southern California researcher, said in a linked editorial that understanding symptoms and recovery in long COVID was crucial for policy making and treatment decisions. Future treatments, clinical trials and policy interventions “will depend on robust studies based on high-quality population level data,” Wu wrote.

Patients should be more closely involved in the design and conduct of these studies going forward, he added.

More information

The U.S. Centers for Disease Control and Prevention has more on long COVID.

SOURCE: BMJ, news release, May 31, 2023