# Vitamin D Status and Incidence of SARS-CoV-2 Reinfections in the Borriana COVID-19 Cohort: A Population-Based Prospective Cohort Study

## TL;DR

This study found that low vitamin D levels are linked to a higher risk of SARS-CoV-2 reinfections, suggesting maintaining sufficient vitamin D could help prevent reinfections.

## Contribution

The study provides new evidence on the relationship between vitamin D status and SARS-CoV-2 reinfection risk in a population-based cohort.

## Key findings

- Deficient and insufficient vitamin D levels were associated with higher reinfection rates compared to sufficient levels.
- A significant inverse dose–response relationship was observed between vitamin D status and reinfection risk.
- Maintaining a vitamin D level of at least 30 ng/mL is recommended to reduce reinfection risk.

## Abstract

A deficient vitamin D (VitD) status has been associated with SARS-CoV-2 infections, severity, and mortality. However, this status related to SARS-CoV-2 reinfections has been studied little. Our aim was to quantify the risk of reinfections considering VitD status before reinfection. Methods: We performed a population-based prospective cohort study in Borriana (Valencia Community, Spain) during 2020–2023, measuring 25-hydroxyvitamin D [25(OH)D] levels by electrochemiluminescence. Cox proportional hazards models were employed. Results: Of a total of 644 SARS-CoV-2 cases with confirmed laboratory tests, 378 (58.9%) were included in our study, with an average age of 38.8 years; 241 were females (63.8%), and 127 reinfections occurred (33.6%). SARS-CoV-2 reinfection incidence rates per 1000 person-days by VitD status were 0.50 for a deficient status (<20 ng/mL), 0.50 for an insufficient status (20–29 ng/mL), and 0.37 for a sufficient status (≥30 ng/mL). Compared with a sufficient VitD status, adjusted hazard ratios were 1.79 (95% confidence interval [CI] 0.89–3.59) for a deficient status and 1.59 (95% CI 1.06–2.38) for an insufficient status with a significant inverse dose–response (p = 0.02). These results can help improve nutritional actions against SARS-CoV-2 reinfections. Conclusions: These results suggest that a VitD status lower than 30 ng/mL showed a higher risk of SARS-CoV-2 reinfection. Achieving and maintaining a sufficient VitD status is recommended to prevent reinfections.