The incubation period of COVID-19: A scoping review and meta-analysis to aid modelling and planning

  1. Prakashini Banka
  2. Catherine Comiskey

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Abstract

Background

An accurate estimate of the distribution of the incubation period for COVID-19 is the foundational building block for modelling the spread of the SARS COV2 and the effectiveness of mitigation strategies on affected communities. Initial estimates were based on early infections, the aim of this study was to provide an updated estimate and meta-analysis of the incubation period distribution for COVID-19.

Methods

The review was conducted according to the PRISMA Scoping Review guidelines. Five databases were searched; CINAHL, MEDLINE, PUBMED, EMBASE, ASSIA, and Global Index Medicus for studies published between 1 January 2020 - 27 July 2020.

Results

A total of 1,084 articles were identified through the database searches and 1 article was identified through the reference screening of retrieved articles. After screening 64 articles were included. The studies combined had a sample of 45,151 people. The mean of the incubation periods was 6.71 days with 95% CIs ranging from 1 to 12.4 days. The median was 6 days and IQR ranging from 1.8 to 16.3. The resulting parameters for a Gamma Distribution modelling the incubation period were Γ( α, λ ) = Γ(2.810,0.419) with mean, μ = α / λ .

Conclusion

Governments are planning their strategies on a maximum incubation period of 14 days. While our results are limited to primarily Chinese research studies, the findings highlight the variability in the mean period and the potential for further incubation beyond 14 days. There is an ongoing need for detailed surveillance on the timing of self-isolation periods and related measures protecting communities as incubation periods may be longer.

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  1. Version published to 10.1101/2020.10.20.20216143v2 on medRxiv
  2. ScreenIT

    SciScore for 10.1101/2020.10.20.20216143: (What is this?)

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

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    Five databases were searched; CINAHL, MEDLINE, PUBMED, EMBASE, ASSIA, and Global Index Medicus for studies published between 1 January 2020 and 27 July 2020.
    MEDLINE
    suggested: (MEDLINE, RRID:SCR_002185)
    EMBASE
    suggested: (EMBASE, RRID:SCR_001650)
    Data was imported into EndNote version x9 and Excel was also used for data extraction.
    Excel
    suggested: None
    Duplicates were removed using EndNote and another duplicate check was conducted manually.
    EndNote
    suggested: (EndNote, RRID:SCR_014001)

    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: We detected the following sentences addressing limitations in the study:
    A limitation of our results is however the lack of published data on the variability in mean times. Of the 64 papers included in the review only 30 reported mean incubation period times and only 4 reported standard deviations or variance. This lack of information on the variability in mean times will undoubtedly introduce a level of uncertainty and bias into the Gamma distribution parameter estimates. Furthermore, the range in mean values reported across the 30 studies varied greatly. Clearly the quality of some studies was lacking, and this assessment of quality was by definition outside the stated objectives of a scoping g review. None the less, this scoping review has provided the first meta-analysis of 64 studies published from January to July 2020. In spite of the provision of 95% confidence intervals for the mean incubation period it was not clear from the studies how these intervals were computed and estimates of the variance and standard deviation could not be computed from them using standard formulae. Given the lack of clarity on the variance and hence standard deviation it is recommended that in future research greater attention is given to the computation details and formula used are provided. To conclude, for the planning and provision of mitigation strategies and advice on isolation periods for the general public, it is essential that an accurate and update estimate of the incubation period is maintained as the SARS COV2 virus spreads. It is equally essential th...

    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.

    About SciScore

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  3. Version published to 10.1101/2020.10.20.20216143v1 on medRxiv