children age \< 5 years are excluded from being randomised to therapy but can contribute to the outcome measures if they are swab negative on day 1. * documented heparin allergy * previous documented heparin induced thrombocytopenia (hit) * recurrent epistaxis that has required hospitalisation in last 3 months * \>72 hours since index case tested positive * inability to provide patient information and consent forms or study instructions in a language in which the patient is competent. * household members who are swab positive on day 1 are excluded from contributing to the primary outcome, but are randomised and still contribute to secondary outcomes

children age \< 5 years are excluded from being randomised to therapy but can contribute to the outcome measures if they are swab negative on day 1. * documented heparin allergy * previous documented heparin induced thrombocytopenia (hit) * recurrent epistaxis that has required hospitalisation in last 3 months * \>72 hours since index case tested positive * inability to provide patient information and consent forms or study instructions in a language in which the patient is competent. * household members who are swab positive on day 1 are excluded from contributing to the primary outcome, but are randomised and still contribute to secondary outcomes

children age < 5 years are excluded from being randomised to therapy but can contribute to the outcome measures if they are swab negative on day 1. documented heparin allergy previous documented heparin induced thrombocytopenia (hit) recurrent epistaxis that has required hospitalisation in last 3 months >72 hours since index case tested positive inability to provide patient information and consent forms or study instructions in a language in which the patient is competent. household members who are swab positive on day 1 are excluded from contributing to the primary outcome, but are randomised and still contribute to secondary outcomes

children age < 5 years are excluded from being randomised to therapy but can contribute to the outcome measures if they are swab negative on day 1. documented heparin allergy previous documented heparin induced thrombocytopenia (hit) recurrent epistaxis that has required hospitalisation in last 3 months >72 hours since index case tested positive inability to provide patient information and consent forms or study instructions in a language in which the patient is competent. household members who are swab positive on day 1 are excluded from contributing to the primary outcome, but are randomised and still contribute to secondary outcomes