inclusion criteria: * covid-19 negative using rapid antigen test at screening. * able and willing to provide written informed consent to take part in the study. * able and willing to provide adequate information for locator purposes. * availability to return for all study visits, barring unforeseen circumstances. * agree not to participate in other research studies involving drugs and/or medical devices during the study period. * female participants must meet the following criteria: postmenopausal or using (or willing to use) an acceptable form of contraception (e.g., barrier method, iud, hormonal contraception, sexual abstinence, surgical sterilization, or vasectomization of male partner). if the female participant has female partners only, the method of contraception will be noted as a barrier method for study documentation. not be pregnant at the baseline or enrollment visit. not be breastfeeding at screening or intend to breastfeed during study participation per participant report. * willingness and ability to defer vaccinations until after study participation is completed. this does not include covid-19 vaccinations. * participants should have received all covid-19 vaccines that they are eligible for. those eligible for booster doses will not delay getting their dose for purposes of enrolling in the study. they will first obtain their booster dose and be re-evaluated for enrollment 2 weeks following their booster dose. * willingness to perform at-home study product self-administration according to written instructions that will be provided. * willingness to follow local guidelines for mask-wearing and face coverings. * must be in general good health in the opinion of the investigator.

inclusion criteria: * covid-19 negative using rapid antigen test at screening. * able and willing to provide written informed consent to take part in the study. * able and willing to provide adequate information for locator purposes. * availability to return for all study visits, barring unforeseen circumstances. * agree not to participate in other research studies involving drugs and/or medical devices during the study period. * female participants must meet the following criteria: postmenopausal or using (or willing to use) an acceptable form of contraception (e.g., barrier method, iud, hormonal contraception, sexual abstinence, surgical sterilization, or vasectomization of male partner). if the female participant has female partners only, the method of contraception will be noted as a barrier method for study documentation. not be pregnant at the baseline or enrollment visit. not be breastfeeding at screening or intend to breastfeed during study participation per participant report. * willingness and ability to defer vaccinations until after study participation is completed. this does not include covid-19 vaccinations. * participants should have received all covid-19 vaccines that they are eligible for. those eligible for booster doses will not delay getting their dose for purposes of enrolling in the study. they will first obtain their booster dose and be re-evaluated for enrollment 2 weeks following their booster dose. * willingness to perform at-home study product self-administration according to written instructions that will be provided. * willingness to follow local guidelines for mask-wearing and face coverings. * must be in general good health in the opinion of the investigator.

inclusion criteria: covid-19 negative using rapid antigen test at screening. able and willing to provide written informed consent to take part in the study. able and willing to provide adequate information for locator purposes. availability to return for all study visits, barring unforeseen circumstances. agree not to participate in other research studies involving drugs and/or medical devices during the study period. female participants must meet the following criteria: postmenopausal or using (or willing to use) an acceptable form of contraception (e.g., barrier method, iud, hormonal contraception, sexual abstinence, surgical sterilization, or vasectomization of male partner). if the female participant has female partners only, the method of contraception will be noted as a barrier method for study documentation. not be pregnant at the baseline or enrollment visit. not be breastfeeding at screening or intend to breastfeed during study participation per participant report. willingness and ability to defer vaccinations until after study participation is completed. this does not include covid-19 vaccinations. participants should have received all covid-19 vaccines that they are eligible for. those eligible for booster doses will not delay getting their dose for purposes of enrolling in the study. they will first obtain their booster dose and be re-evaluated for enrollment 2 weeks following their booster dose. willingness to perform at-home study product self-administration according to written instructions that will be provided. willingness to follow local guidelines for mask-wearing and face coverings. must be in general good health in the opinion of the investigator.

inclusion criteria: covid-19 negative using rapid antigen test at screening. able and willing to provide written informed consent to take part in the study. able and willing to provide adequate information for locator purposes. availability to return for all study visits, barring unforeseen circumstances. agree not to participate in other research studies involving drugs and/or medical devices during the study period. female participants must meet the following criteria: postmenopausal or using (or willing to use) an acceptable form of contraception (e.g., barrier method, iud, hormonal contraception, sexual abstinence, surgical sterilization, or vasectomization of male partner). if the female participant has female partners only, the method of contraception will be noted as a barrier method for study documentation. not be pregnant at the baseline or enrollment visit. not be breastfeeding at screening or intend to breastfeed during study participation per participant report. willingness and ability to defer vaccinations until after study participation is completed. this does not include covid-19 vaccinations. participants should have received all covid-19 vaccines that they are eligible for. those eligible for booster doses will not delay getting their dose for purposes of enrolling in the study. they will first obtain their booster dose and be re-evaluated for enrollment 2 weeks following their booster dose. willingness to perform at-home study product self-administration according to written instructions that will be provided. willingness to follow local guidelines for mask-wearing and face coverings. must be in general good health in the opinion of the investigator.