inclusion criteria: * age \>=1 year (as children \<1 year may not be able to take oral probiotics) * household contact of someone diagnosed with covid-19 * willingness to stop taking other probiotics or to not take any other probiotic while on lgg/placebo (taking a probiotic at the time of screening will not be considered a reason for exclusion. however, subjects will be asked to stop taking their probiotic if they enroll on the study). * access to e-mail/internet to complete electronic consent via redcap

inclusion criteria: * age \>=1 year (as children \<1 year may not be able to take oral probiotics) * household contact of someone diagnosed with covid-19 * willingness to stop taking other probiotics or to not take any other probiotic while on lgg/placebo (taking a probiotic at the time of screening will not be considered a reason for exclusion. however, subjects will be asked to stop taking their probiotic if they enroll on the study). * access to e-mail/internet to complete electronic consent via redcap

inclusion criteria: - age >=1 year (as children <1 year may not be able to take oral probiotics) - household contact of someone diagnosed with covid-19 - willingness to stop taking other probiotics or to not take any other probiotic while on lgg/placebo (taking a probiotic at the time of screening will not be considered a reason for exclusion. however, subjects will be asked to stop taking their probiotic if they enroll on the study). - access to e-mail/internet to complete electronic consent via redcap

inclusion criteria: - age >=1 year (as children <1 year may not be able to take oral probiotics) - household contact of someone diagnosed with covid-19 - willingness to stop taking other probiotics or to not take any other probiotic while on lgg/placebo (taking a probiotic at the time of screening will not be considered a reason for exclusion. however, subjects will be asked to stop taking their probiotic if they enroll on the study). - access to e-mail/internet to complete electronic consent via redcap