Comparison of strategies for daily surveillance of international travellers quarantined in Vanuatu, October-December 2020.

Objective: To prevent importation of coronavirus disease 2019 (COVID-19) to Vanuatu, since March 2020, all travellers to the country have been required to complete a 14-day quarantine in a government-designated facility. A short message service (SMS, or "text message") system was developed to collect information on symptoms of COVID-19 among travellers in quarantine. A trial within a cohort study was conducted among travellers arriving to Vanuatu by air from 27 October to 7 December 2020 to assess SMS acceptability, efficiency and utility and whether SMS-based health monitoring was as effective as in-person monitoring in identifying people with COVID-19 symptoms. Methods: Control group participants received standard monitoring (daily in-person visits) and participants in the intervention group received a daily SMS text requesting a response coded for symptom development. Differences between the two groups were determined using χ2 tests. Results: Of the 495 eligible travellers, 423 participated; 170 were allocated to the control group and 253 to the intervention group. At least one return SMS text was received from 50% (107/212) of participants who were confirmed to have received an SMS text. Less than 2% (4/253) of the intervention group and 0% of the control group reported symptoms. Discussion: The SMS intervention had a high level of acceptability. SMS is a useful tool to monitor symptom development among people in quarantine and for broader public health programmes that require follow up.