COVID-19 international border surveillance at Toronto’s Pearson Airport: a cohort study

  1. Vivek Goel
  2. David Bulir
  3. Eric De Prophetis
  4. Munaza Jamil
  5. Laura C Rosella
  6. Dominik Mertz
  7. Cheryl Regehr
  8. Marek Smieja

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Abstract

The primary objective was to estimate the positivity rate of air travellers coming to Toronto, Canada in September and October 2020, on arrival and on day 7 and day 14. The secondary objectives were to estimate the degree of risk based on country of origin and to assess knowledge and attitudes towards COVID-19 control measures and subjective well-being during the quarantine period.

Design

Prospective cohort of arriving international travellers.

Setting

Toronto Pearson Airport Terminal 1, Toronto, Canada.

Participants

Participants of this study were passengers arriving on international flights. Inclusion criteria were those aged 18 or older who had a final destination within 100 km of the airport, spoke English or French, and provided consent. Excluded were those taking a connecting flight, had no internet access, exhibited symptoms of COVID-19 on arrival or were exempted from quarantine.

Main outcome measures

Positive for SARS-CoV-2 virus on reverse transcription PCR with self-administered oral-nasal swab and general well-being using the WHO-5 Well-being Index.

Results

Of 16 361 passengers enrolled, 248 (1.5%, 95% CI 1.3% to 1.7%) tested positive. Of these, 167 (67%) were identified on arrival, 67 (27%) on day 7, and 14 (6%) on day 14. The positivity rate increased from 1% in September to 2% in October. Average well-being score declined from 19.8 (out of a maximum of 25) to 15.5 between arrival and day 7 (p<0.001).

Conclusions

A single arrival test will pick up two-thirds of individuals who will become positive by day 14, with most of the rest detected on the second test on day 7. These results support strategies identified through mathematical models that a reduced quarantine combined with testing can be as effective as a 14-day quarantine.

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  1. Version published to 10.1136/bmjopen-2021-050714
  2. ScreenIT

    SciScore for 10.1101/2021.02.25.21252404: (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
    The items were drawn from the World Health Organization Survey Tool and Guidance for Rapid, Simple, Flexible Behavioural Insights on COVID-19.15 Laboratory Methods: Swabs collected in McMaster Molecular Medium (MMM) were batch-processed from nucleic acid extraction to RT-qPCR set-up on the Hamilton Microlab® STAR (Hamilton Company, Nevada, USA).
    STAR
    suggested: (STAR, RRID:SCR_015899)

    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:
    Limitations: This study was conducted at a single terminal at Toronto’s Pearson Airport, albeit representing the majority of international flights arriving at Canada’s busiest airport. We enrolled approximately 20% of passengers. We believe that up to one-half of the arriving passengers would have met our exclusion criteria, so our participation rate likely approached 40%. There will likely have been selection bias in our participants. However, it is uncertain what the direction may have been. It may be possible that those who engaged in higher risk behaviours while abroad may have chosen not to participate. On the other hand, during the study period, PCR testing was not broadly available in Ontario, and some participants told us they took part in order to access the free testing. Regardless, selection bias would affect the overall positivity rate. However, a key value of our results is the distribution of positivity across the three timepoints, which should not be affected by selection bias. We had losses to follow-up, and these may have biased the results if those who broke quarantine or developed symptoms might have been less likely to participate, or less likely to follow-up. We adjusted using a sensitivity analysis and inverse probability weighting, with similar results using both methods. IPW were based only on the variables that were measured and thus selection bias due to unmeasured factors may not be accounted for. The overall conclusions are not changed with either ...

    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.
    • Thank you for including a protocol registration statement.

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  3. Version published to 10.1101/2021.02.25.21252404v1 on medRxiv