1. Heimer KA, Hart AM, Martin LG, Rubio-Wallace S. Examining the evidence for the use of vitamin C in the prophylaxis and treatment of the common cold. J Am Acad Nurse Pract. 2009;21(5):295–300.
2. Douglas RM, Hemila H, Chalker E, Treacy B. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2007;18(3):CD000980.
3. Furuya A, Uozaki M, Yamasaki H, Arakawa T, Arita M, Koyama AH. Antiviral effects of ascorbic and dehydroascorbic acids in vitro. Int J Mol Med. 2008;22(4):541–5.
4. Kim Y, Kim H, Bae S, et al. Vitamin C is an essential factor on the anti-viral immune responses through the production of interferon-α/β at the initial stage of influenza A virus (H3N2) infection. Immune network, 2013, 13(2): 70-74.
5. Bergman P, Lindh AU, Bjorkhem-Bergman L, Lindh JD. Vitamin D and respiratory tract infections: a systematic review and meta-analysis of randomized controlled trials. PLoS one. 2013;8(6):e65835.
6. Charan J, Goyal JP, Saxena D, Yadav P. Vitamin D for prevention of respiratory tract infections: a systematic review and meta-analysis. Journal of Pharmacology and Pharmacotherapeutics. 2012;3(4):300-303.
7. Martineau AR, Jolliffe DA, Hooper RL, Greenberg L, Aloia JF, Bergman P, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017;356:i6583.
8. Hemilä, Harri. "Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage." JRSM open 8.5 (2017): 2054270417694291.
9. Johnstone, Jennie, et al. "Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials." CMAJ 184.10 (2012): E551-E561.
10. Rao, Goutham, and Kate Rowland. "Zinc for the common cold—not if, but when." The Journal of family practice 60.11 (2011): 669.
11. Lassi, Zohra S., Anoosh Moin, and Zulfiqar A. Bhutta. "Zinc supplementation for the prevention of pneumonia in children aged 2 months to 59 months." Cochrane Database of Systematic Reviews 12 (2016).
12. Chen, Hengxi, et al. "Vitamin A for preventing acute lower respiratory tract infections in children up to seven years of age." Cochrane Database of Systematic Reviews 1 (2008).
13. Wang, Yizhong, et al. "Probiotics for prevention and treatment of respiratory tract infections in children: A systematic review and meta-analysis of randomized controlled trials." Medicine 95.31 (2016).
14. Bo, Lulong, et al. "Probiotics for preventing ventilator‐associated pneumonia." Cochrane Database of Systematic Reviews 10 (2014).
15. Laursen, Rikke Pilmann, and Iva Hojsak. "Probiotics for respiratory tract infections in children attending day care centers—a systematic review." European journal of pediatrics 177.7 (2018): 979-994.
16. Tiralongo, Evelin, Shirley S. Wee, and Rodney A. Lea. "Elderberry supplementation reduces cold duration and symptoms in air-travellers: a randomized, double-blind placebo-controlled clinical trial." Nutrients 8.4 (2016): 182.
17. Zakay-Rones, Z., et al. "Randomized study of the efficacy and safety of oral elderberry extract in the treatment of influenza A and B virus infections." Journal of International Medical Research 32.2 (2004): 132-140.
18. Hawkins, Jessie, et al. "Black elderberry (Sambucus nigra) supplementation effectively treats upper respiratory symptoms: A meta-analysis of randomized, controlled clinical trials." Complementary therapies in medicine 42 (2019): 361-365.
19. Ho, Giang Thanh Thi, Helle Wangensteen, and Hilde Barsett. "Elderberry and elderflower extracts, phenolic compounds, and metabolites and their effect on complement, RAW 264.7 macrophages and dendritic cells." International journal of molecular sciences 18.3 (2017): 584.