Risk Factors of COVID-19 Infection and the Effectiveness of Pre-flight Screening from an Investigation of an International Flight to Thailand, 2020

Abstract

Thailand implemented pre-flight screening (reverse transcription polymerase chain reaction test for SARS-CoV-2 within 72 hours before departure) to mitigate the importation of COVID-19 during the early phase of the pandemic. We conducted a cross-sectional study to identify factors associated with COVID-19 infection and assess the effectiveness of pre-flight screening among passengers on an India-to-Thailand flight in August 2020. Logistic regression was used to determine the association between the possession of COVID-Free Certificate (CFC) and a positive SARS-CoV-2 test result upon arrival. Twenty-three of 209 passengers (11.0%) had a positive SARS-CoV-2 test. Among 142 CFC holders, 10 (7.0%) tested positive, while 13 of 58 (22.4%) passengers without a CFC tested positive upon arrival (p-value 0.003), equivalent to a case reduction of 68.8%. CFC possession yielded an adjusted odds ratio (AOR) of 0.04 (95% CI 0.01–0.44). Being a massage therapist (AOR 17.04, 95% CI 2.37–122.37) and using public transportation in India (AOR 5.30, 95% CI 1.49–18.77) were significantly associated with COVID-19 infection. With the unavailability of vaccines, people should be mindful of taking local public transportation during a pandemic, particularly when planning to travel abroad. Pre-flight screening is an effective method in reducing positive cases from international travel.