Study aim: Comparative determination of the effect of two solutions of Chlorhexidine and sodium bicarbonate mouthwash on the onset of symptoms attributed to Covid-19 in vaccinated operating room staff of selected hospitals of Isfahan University of Medical Sciences in 2022 Design: A controlled clinical trial with parallel, double-blind, randomized groups on 120 patients. To divide the subjects into intervention and control groups, random allocation method and table of random numbers will be used. Settings and conduct: This study will be performed in selected hospitals of Isfahan. The intervention groups will receive Chlorhexidine mouthwash and sodium bicarbonate mouthwash and the control group receives placebo. Mouthwash and placebo will be used for two weeks, twice a day, 15 ml each time for one minute. From the start of mouthwash solutions until four weeks later, the studied samples will be monitored. To double-blind the study, participants will be unaware of the type of mouthwash solution and the data analyzer will be unaware of the details of the grouping. Participants/Inclusion and exclusion criteria: Get at least two doses of the vaccine, Personnel range of 18-60 years, Do not get Covid-19 in the last two months, No symptoms of systemic infection, Do not take immunosuppressive drugs, No history of allergy to mouthwash solutions, At least 2 weeks have passed since the second dose of the vaccine was given, No pregnancy, No breastfeeding Intervention groups: The intervention groups will receive chlorhexidine mouthwash and sodium bicarbonate mouthwash, and the control group received placebo (water). Mouthwash and placebo will use for two weeks, twice a day, 15 ml each time for one minute. From the start of mouthwash solutions until four weeks later, the samples will be monitored for symptoms. If necessary, PCR test will also be taken. Main outcome variables: Covid-19 symptoms, PCR test