Transmission of SARS-CoV-2 in the household setting: A prospective cohort study in children and adults in England.

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.