Approximately 20-30% of individuals who contract COVID-19 will experience prolonged symptoms 3-6 months after acute infection; symptom severity may range from inconvenient to insurmountable.
We are still living in the shadow of COVID-19, but some individuals who were infected early in the pandemic can be evaluated to determine longer term symptoms and health outcomes of long COVID. One study, recently published in The BMJ, aimed to comprehensively characterize post–COVID-19 condition in a population-based, longitudinal cohort of individuals who had previously contracted COVID-19.
The investigators described patterns of recovery and symptom persistence over a 2-year period, seeking to determine the risk of related symptoms by comparing their prevalence in a general population cohort who were never infected with COVID-19. Utilizing the ongoing population-based, prospective Zurich SARS-CoV-2 Cohort study, the investigators recruited individuals with a confirmed COVID-19 diagnosis. Eligible participants were 18 years and older, resided in Zurich, and were sufficient in the German language.
From August 6, 2020-January 19, 2021, participants who PCR tested positive for COVID-19 were enrolled in the study. The study patients had all been infected with the earliest iteration of COVID-19, the wildtype Wuhan-Hu-1 strain. All individuals contracted COVID-19 before vaccines were made available.
The primary study outcome was the overall relative health status of participants at 6, 12, 18, and 24 months after infection. Participants were asked whether they had recovered compared to their usual health before COVID-19, and their overall health was evaluated using the EuroQol visual analogue scale. Secondary outcomes included the prevalence and severity of 23 long COVID symptoms.
A total of 1106 Zurich SARS-CoV-2 Cohort patients consented to participate in this study, with 72% (n = 788) completing the 24-month assessment. Of 1106 study patients, 51.2% were female. During acute COVID-19 infection, 86.0% (n = 951) were symptomatic and 4.3% (48) were hospitalized.
Overall, 55.3% of participants reported returning to their normal health status within a month of contracting COVID-19. Within 1-3 months, another 17.6% reported they had recovered. At 6 months, 22.9% of participants had not yet recovered. Among them, 16.2% had mild symptoms, 3.6% had moderate symptoms, and 2.7% had severe health impairment.
At 12 months after acute infection, the participants reporting nonrecovery was reduced to 18.5%. After 18 months, this fell to 17.2%. Severity of health impairment also decreased at 24 months after acute infection, with 10.4% reporting mild symptoms, 3.9% reported moderate symptoms, and 1.9% reported severe impairment.
According to self-reported health status over time, 68.4% of participants had a continued recovery and 13.5% had an overall improvement. However, 5.2% of the study patients experienced a worsening of health status, with 4.4% reported alternating periods of recovery and health impairment.
After 24 months, 1 in 6 of the unvaccinated participants reported they were still experiencing health repercussions from COVID-19 infection. The investigators confirmed symptom prevalence with a cohort of individuals who had never contracted COVID-19. The highest symptoms reported were altered taste or smell (9.8%), post-exertional malaise (9.4%), fatigue (5.4%), dyspnea (7.8%), reduced concentration (8.3%), and memory impairment (5.7%).
The investigators noted their finding that 18% of unvaccinated individuals had post–COVID-19 condition up to 2 years after infection aligns with prior research. Symptom severity and health impairment did reduce over time, but further study is needed to establish effective interventions to combat long COVID.