Prevalence and determinants of long COVID and SARS-CoV-2 reinfection in the Spanish adult population: A nationwide public health survey.

INTRODUCTION

Long COVID is an emerging public health concern with heterogeneous prevalence. Evidence on the impact of reinfection and vaccination remains limited, especially in Spain.

METHODS

We conducted a prospective online cohort survey between January 2024 and April 2025, gathering data on demographics, vaccination, symptoms, comorbidities, and reinfection history from Spanish adults (n=1018). Long COVID was defined per NICE guidelines as symptoms persisting beyond eight weeks after viral clearance. Multivariate logistic regression identified associated factors.

RESULTS

Of 972 participants (332 men, 640 women), long COVID prevalence was 14.3% (n=139). Female sex (OR: 1.70; 95% CI: 1.10-2.57; p=0.014) and chronic obstructive pulmonary disease (COPD) (OR: 4.14; 95% CI: 1.28-13.42; p=0.018) increased risk. Mixed vaccination schedules raised risk compared to Pfizer-only regimens (OR: 1.30; 95% CI: 1.04-1.62; p=0.020). Reinfection, reported by 47.2%, was also a risk factor (OR: 1.64; 95% CI: 1.12-2.42; p=0.012). Frequent long COVID symptoms included anosmia, dyspnea, pneumonia, and myalgia.

CONCLUSIONS

This national cohort underscores the persistent burden of long COVID in Spain. Female sex, COPD, reinfection, and mixed vaccination schedules are key associated factors, with implications for targeted prevention strategies and vaccination policies.