Feasibility of using community pharmacy sales of over-the-counter respiratory products as a syndromic surveillance indicator: a pilot study from Sofia, Bulgaria.

INTRODUCTION

Data on sales of pharmaceutical products (SPP) for symptomatic treatment of acute respiratory diseases can be a reliable indicator providing initial information before official surveillance systems. This pilot study aimed to develop a framework for collecting community pharmacy sales data and assess the feasibility of using these data as a complementary indicator of respiratory infection activity.

METHODS

Products were selected through observation of prime-time television advertisements during February-March 2025, expert review, and a survey of 97 community pharmacists. Retrospective monthly sales data for selected product categories were obtained from two community pharmacies in Sofia for October 2024-April 2025. Sales were analysed using descriptive statistics, the Friedman test, and post-hoc Wilcoxon signed-rank tests with Bonferroni correction.

RESULTS

Mean SPP vary from 121.06 units for antivirals to 685.96 units for antipyretics. Antivirals showed the greatest relative monthly variability (R = 216.4, CV = 64.78), followed by food supplements (R = 160.16, CV = 33.23). Sales of products for sore throat were comparatively stable (R = 103, CV = 18.62) with limited temporal variation during the observation period. Antipyretic and antiviral sales reached their highest levels in January 2025, accounting for 19.14 and 32.00% of their respective total sales during the observation period. The January increase temporally coincided with the peak in reported acute respiratory infections in Sofia during week 4 of 2025. However, pairwise comparisons between January and the other months were not statistically significant after Bonferroni correction.

CONCLUSION

Pharmacy sales data showed preliminary potential for monitoring local respiratory infection trends; however, larger prospective multicenter studies using standardized product classifications and higher-frequency sales data are needed to evaluate their contribution to complementary respiratory syndromic surveillance.