Assessing the asymptomatic proportion of SARS-CoV-2 infection with age in China before mass vaccination

  1. Zengmiao Wang
  2. Peiyi Wu
  3. Jingyuan Wang
  4. José Lourenço
  5. Bingying Li
  6. Benjamin Rader
  7. Marko Laine
  8. Hui Miao
  9. Ligui Wang
  10. Hongbin Song
  11. Nita Bharti
  12. John S. Brownstein
  13. Ottar N. Bjornstad
  14. Christopher Dye
  15. Huaiyu Tian

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Abstract

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.

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  1. Version published to 10.1098/rsif.2022.0498
  2. ScreenIT

    SciScore for 10.1101/2021.09.03.21262757: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Ethicsnot detected.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    The definition for asymptomatic and symptomatic SARS-CoV-2 cases Suspected COVID-19 case: Individuals who have any one of the epidemiological histories, and meet any two of the clinical manifestations; if there is no clear epidemiological history, meet any 2 of the clinical manifestations, and the SARS-CoV-2-specific IgM antibody is positive; or meets 3 of the clinical manifestations.
    SARS-CoV-2-specific IgM
    suggested: None
    ) SARS-CoV-2-specific IgG antibody turns from negative to positive or the IgG antibody titer in the recovery phase is 4 times or more higher than that in the acute phase.
    SARS-CoV-2-specific IgG
    suggested: None
    IgG
    suggested: None

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

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  3. Version published to 10.1101/2021.09.03.21262757v1 on medRxiv