Up to 60% of health care workers may have long COVID 4 years after infection

Four years after infection with the wild-type SARS-CoV-2 strain, up to 60% of health care workers (HCWs) in Switzerland still reported at least one COVID-19 symptom, although the number of participants dwindled over time, Swiss researchers write in Infection.

From 2022 to 2024, the team tracked 24 COVID-19 symptoms among 456 HCWs who self-reported infection with the original SARS-CoV-2 strain and 571 uninfected controls at 14 centers. Participants completed an online survey at baseline and every six months and underwent serologic testing to identify any asymptomatic infections. The median participant age was 44 years, and 80.6% were women. 

Long COVID is also called post-acute COVID-19 sequelae (PASC).

“Comparative analyses show that the risk of developing PASC is highest after infection with ancestral SARS-CoV-2 (aSCV2) and decreases with subsequent variants,” the study authors noted. 

Most symptoms became less common

Participants completed a median of three of five surveys. A total of 72.0% of participants lacked complete data or were lost to follow-up during the study. Relative to controls, infected participants were younger (median age, 41 vs 47 years), more often employed as nurses (59.4% vs 37.5%), and had children younger than six years at home (13.6% vs 9.3%), while a smaller percentage smoked (13.6% vs 21.4%).

At baseline, 40.8% of infected participants reported one or more long-COVID symptoms. Thirteen of 24 symptoms were more common in COVID-19 survivors than in controls, most commonly fatigue (22.8%), loss of smell or taste (11.4%), and brain fog (8.3%). 

The median number of symptoms declined from two at baseline to zero in the final survey and from two to one in the 52 participants with complete data. The decline was most pronounced from baseline to the first follow-up survey and stayed mostly stable thereafter.

Most symptoms declined in prevalence up to the last survey (median, four years after infection), while 41 of 70 (58.6%) remaining participants continued to report at least one symptom. In total, 70 (37.6%) of 186 participants reported having subjective long COVID, which was tied to greater symptom burden. Nine of 70 participants (12.9%) reported resolution of symptoms at the first follow-up, after which there were no new reports of resolved symptoms.

Few participants remained at final follow-up

At the final follow-up, only 18 of the remaining 70 participants remained, with 14 (78%) indicating ongoing subjective long COVID. Scores on the Post-COVID Functional Status scale showed slight impairment in most participants, but moderate to severe limitations often lingered.

We demonstrate a non-linear decline in PASC-specific symptoms over time, with up to 60% of individuals still reporting symptoms after a median of almost 4 years after aSCV2 infection.

Of participants with complete data, those with an initially high number of symptoms tended to have higher symptom scores in the last survey.

“In a prospective multicentre cohort of HCWs, we demonstrate a non-linear decline in PASC-specific symptoms over time, with up to 60% of individuals still reporting symptoms after a median of almost 4 years after aSCV2 infection,” the researchers wrote. “Consistent with previous reports of neurological symptoms persisting, brain fog showed no significant decline, suggesting ongoing cognitive impairment in PASC affected patients.”

The authors called for long COVID to be recognized as a chronic condition requiring long-term clinical and social support, as well as for further research to clarify pathophysiologic factors and identify diagnostic markers and effective treatment.

“Our findings indicate that full recovery from PASC remains uncertain for many patients, and functional limitations persist,” they concluded. “As our cohort consists of HCWs, these findings underline the need for occupational health strategies, including structured return-to-work programs and flexible workload adjustments, to support sustainable reintegration and minimize the loss of essential workforce.”