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Assessing the Asymptomatic Proportion of Sars-Cov-2 Infection With Age in China Before Mass Vaccination

Z. Wang, P. Wu, J. Wang, J. Lourenço, B. Li, B. Rader, M. Laine, H. Miao, L. Wang, H. Song, N. Bharti, J. Brownstein, O. Bjornstad, C. Dye, H. Tian

Journal of the Royal Society Interface, 2022

Some asymptomatic individuals carrying SARS-CoV-2 can transmit the virus and contribute to outbreaks of COVID-19. Here, we use detailed surveillance data gathered during COVID-19 resurgences in six cities of China at the beginning of 2021 to investigate the relationship between asymptomatic proportion and age. Epidemiological data obtained before mass vaccination provide valuable insights into the nature of pathogenicity of SARS-CoV-2. The data were collected by multiple rounds of city-wide PCR testing with contact tracing, where each patient was monitored for symptoms through the whole course of infection. The clinical endpoint (asymptomatic or symptomatic) for each patient was recorded (the pre-symptomatic patients were classified as symptomatic). We find that the proportion of infections that are asymptomatic declines with age (coefficient = −0.006, 95% CI: −0.008 to −0.003, p < 0.01), falling from 42% (95% CI: 6–78%) in age group 0–9 years to 11% (95% CI: 0–25%) in age group greater than 60 years. Using an age-stratified compartment model, we show that this age- dependent asymptomatic pattern, together with the distribution of cases by age, can explain most of the reported variation in asymptomatic proportions among cities. Our analysis suggests that SARS-CoV-2 surveillance strategies should take account of the variation in asymptomatic proportion with age.

Assessing the asymptomatic proportion of SARS-CoV-2 infection with age in China before mass vaccination
Assessing the asymptomatic proportion of
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title={Assessing the asymptomatic proportion of SARS-CoV-2 infection with age in China before mass vaccination},

author={Wang, Zengmiao and Wu, Peiyi and Wang, Jingyuan and Lourenco, Jose and Li, Bingying and Rader, Benjamin and Laine, Marko and Miao, Hui and Wang, Ligui and Song, Hongbin and others},

journal={Journal of the Royal Society Interface},





publisher={The Royal Society}