Transmission of SARS-CoV-2 in the household setting: a prospective cohort study in children and adults in England.
Miller E., Waight PA., Andrews NJ., McOwat K., Brown KE., Katja H., Ijaz S., Sinnathamby M., Cuthbertson H., Hallis B., Parimalanathan V., de Lusignan S., Lopez-Bernal J.
OBJECTIVES: To measure secondary attack rates (SARs) in prospectively followed household contacts of paediatric and adult cases of SARS-CoV-2 infection in England. METHODS: Self-taken nasal swabs from household contacts of PCR confirmed cases of COVID-19 and blood samples on day 35 were tested for evidence of infection with SARS-CoV-2 virus. RESULTS: The secondary attack rate (SAR) among 431 contacts of 172 symptomatic index cases was 33% (95% confidence intervals [CI] 25-40) and was lower from primary cases without respiratory symptoms, 6% (CI 0-14) vs 37% (CI 29-45), p=0.030. The SAR from index cases <11 years was 25% (CI 12-38). SARs ranged from 16% (4-28) in contacts <11 years old to 36% (CI 28-45) in contacts aged 19-54 years (p=0.119). The proportion infected who developed symptoms (78%) was similar by age (p=0.44) though <19 year olds had fewer mean number of symptoms than adults (p=0.001) and fewer reported loss of sense of taste or smell (p=0.0001). CONCLUSIONS: There are high risks of transmission of SARS-CoV-2 virus in the home, including those where infection is introduced by a child. The risk of children acquiring infection was lower than that in adults and fewer developed typical symptoms of Covid-19 infection.