Double-blinded randomized research conducted at Cristian Albrechts University evaluated the influence of regular probiotic consumption on upper respiratory tract infections with 479 patients. The results demonstrated a decrease in the symptoms of patients treated with probiotics. Hence, the authors proposed probiotics as a supplement in the treatment of viral respiratory infections. Thereby, I recommend you to consume 6-12 pieces of bee bread, a natural probiotic bee product, daily. You may mix it with your favorite foods or drinks or eat directly.

References:
1. Kieliszek, Marek, et al. ""Pollen and bee bread as new health-oriented products: A review."" Trends in Food Science & Technology 71 (2018): 170-180.
2. De Verse, Michael, et al. ""Probiotic bacteria reduced duration and severity but not the incidence of common cold episodes in a double-blind, randomized, controlled trial."" Vaccine 24.44-46 (2006): 6670-6674.