Can Ship Travel Contain COVID-19 Outbreak after Re-Opening a Bayesian Meta-Analysis

Background: To assess the transmissibility of SARS-CoV-2 on warships and cruise ships and to quantify the effectiveness of containment measures.Methods: Data on COVID-19 outbreaks on cruise ships and warships were retrieved from public messages and literature. The transmission coefficient (β), basic reproductive number (R0), and time to deploy containment measures were estimated by the Bayesian Susceptible-Exposed-Infected-Recovered (SEIR) model. The pooled estimates were computed in a meta-analysis for predicting the protection with or without NPIs (non-pharmaceutical interventions).Results: All these outbreaks on warships and cruise ships led to high but heterogeneous β. NPIs during the voyage could reduce the transmission coefficients of SARS-CoV-2 by 50% estimated form the meta-analyses. Two weeks into the voyage of a cruise that began with 1 infected passenger out of 3711, we estimated there would be 47 (28-72), 9 (7-12), 4 (3-5), and 2 (2-2) final cases under 0%, 50%, 70% and 90% vaccines protection without NPIs, respectively.Conclusions: Timeliness of strict NPIs accompanied with quarantine and isolation is imperative when COVID-19 cases are introduced into cruise ships. Spread of COVID-19 on ships was predicted to be limited in scenarios corresponding to at least 70% protection from prior vaccination across all passengers and crew.