# Interventional Study of Nonpharmaceutical Measures to Prevent COVID-19 Aboard Cruise Ships

## TL;DR

This study shows that wearing masks on cruise ships significantly reduced the risk of COVID-19 infections compared to both unmasked passengers and the general community.

## Contribution

The study provides empirical evidence on the effectiveness of passenger masking in preventing COVID-19 on cruise ships with vaccinated populations.

## Key findings

- Masked passengers had a 14.58 times lower infection risk than unmasked passengers.
- Masked passengers had a 19.61 times lower infection risk than in the community.
- Unmasked passengers had a slightly lower risk than the community but higher than masked passengers.

## Abstract

Cruise ships carrying COVID-19–vaccinated populations applied near-identical nonpharmaceutical measures during July–November 2021; passenger masking was not applied on 2 ships. Infection risk for masked passengers was 14.58 times lower than for unmasked passengers and 19.61 times lower than in the community. Unmasked passengers’ risk was slightly lower than community risk.