Most studies that explore the long-term effects of COVID-19 are based on subjectively reported symptoms, while laboratory-measured biomarkers are mainly examined in studies of relatively small cohorts. This study investigates the long-term effects of SARS-CoV-2 infection on common laboratory biomarkers.

We utilized a retrospective cohort of SARS-CoV-2 infected individuals and rigorously matched controls based on demographic and clinical characteristics, examining 63 common laboratory biomarkers. Additional lab-specific cohorts were matched with an additional criterion of baseline biomarker values. Differences in biomarkers over a 12-month follow-up were analyzed using standardized mean difference-in-differences.

The general cohort included 361,061 matched pairs, with 26M laboratory results. The effects on most biomarkers lasted 1–4 months and were consistent with anticipated changes after acute viral infections. Some biomarkers presented prolonged effects, consistent across the general and lab-specific cohorts. One group of such findings included a 7–8 month decrease in WBC counts, mainly driven by decreased counts of neutrophils, monocytes, and basophils. Potassium levels were decreased for 3–5 months. Vaccinated individuals’ data suggested potentially smaller effects on WBCs, but cohort sizes limited this analysis.

This study explores SARS-CoV-2 infection effects on common laboratory biomarkers, characterizing the direction and duration of these effects on the largest infected cohort to date. The effects of most biomarkers resolve in the first months following infection. The most notable longer-lasting effects involved the immune system. Further research is required to characterize the magnitude of these effects among specific individuals.