Objective To investigate the efficacy and safety of recombinant human interferon alpha1b (rhIFN-α) nasal drops in healthy medical staff to prevent 2019 novel coronavirus disease (COVID-19). Methods A prospective, open-label study was conducted. Starting January 21, 2020, at Taihe Hospital in Shiyan City, Hubei Province, 2944 medical staff members were recruited and allocated into a low-risk group or a high-risk group according to whether they were directly exposed to the coronavirus. Participants in the low-risk group received rhIFN-α nasal drops (2-3 drops/nostril/time, 4 times/day) for 28 days; those in the high-risk group received rhIFN-α nasal drops combined with thymosin-α1 (1.6 mg, hypodermic injection, once a week). The primary outcome was new-onset COVID-19 over 28 days. The secondary outcome was new-onset fever or respiratory symptoms but with negative pulmonary images. The results were compared with the number of new cases in medical staff in the same areas of Hubei Province (including Wuhan) during the same period. Adverse reactions to interferon nasal drops were also observed. Results Among the 2944 subjects in our study, 2415 were included in the low-risk group, including 997 doctors and 1418 nurses with average ages of 37.38 and 33.56 years, respectively; 529 were included in the high-risk group, including 122 doctors and 407 nurses with average ages of 35.24 and 32.16 years, respectively. The 28-day incidence of COVID-19 was zero in both the high- and low-risk groups. The 28-day incidence of new-onset clinical symptoms with negative images for pneumonia was also zero in both the high- and low-risk groups. As controls, a total of 2035 medical personnel with confirmed COVID-19 pneumonia from the same area (Hubei Province) was observed between January 21 to February 23, 2020. There were no serious adverse effects in the 2944 subjects treated during the intervention period. Conclusion In this investigator-initiated open-label study, we observed that rhIFN-α nasal drops can effectively prevent COVID-19 in treated medical personnel. Our results also indicate that rhIFN-α nasal drops have potential promise for protecting susceptible healthy people during the coronavirus pandemic.