Masking Reduced COVID-19 Risk on Cruise Ships, Preventing Disease Spread

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From July to November 2021, cruise ships accommodating COVID-19-vaccinated individuals implemented almost identical nonpharmaceutical protocols.

Gloves, masks, and a cruise ship highlight the importance of maintaining health protocols on ships during disease outbreaks.

Gloves, masks, and a cruise ship highlight the importance of maintaining health protocols on ships during disease outbreaks.

Image credits: Unsplash

During this time, 2 cruise ships did not mandate passenger masking. Masked passengers were found to have a 14.58 times lower risk of infection compared to unmasked passengers and a 19.61 times lower risk compared to individuals in the community. Additionally, the risk for unmasked passengers was slightly lower than that observed within the community.

In the study, Group 1 comprised 2 cruise ships where masking was not enforced among passengers, while Group 2 included 9 ships where passengers wore masks as part of the NPM protocol. The results revealed a disparity in COVID-19 infection risk between the 2 groups. Passengers in Group 2, adhering to masking protocols, exhibited a substantially lower risk compared to Group 1, where masking was not enforced. Moreover, the risk among masked passengers was nearly 20 times lower than that of community members.

3 Key Takeaways

  1. The study highlights the effectiveness of masking in reducing the risk of COVID-19 transmission on cruise ships during the outbreak.
  2. Cruise ships that enforced similar nonpharmaceutical protocols experienced varying levels of infection risk based on whether they mandated passenger masking.
  3. Comparing infection risks onboard cruise ships to those in the community provides valuable context

“Cruise ships are susceptible to outbreaks of influenza, COVID-19, respiratory syncytial virus (RSV), and other viral respiratory infections,” according to the CDC. “Given the demographic composition of cruise ship travelers, including older adults and individuals with underlying medical conditions, the risk of complications from these respiratory viruses is heightened. Early detection, prevention, and control of such infections are crucial not only for the health of passengers and crew but also for preventing the spread of these viruses into communities.”1

The study also highlighted the role of recent vaccination in reducing infection risk among cruise ship populations. With almost 100% vaccination coverage on ships compared to 66% in the community, the impact on infection rates was significant. Despite the highly pathogenic nature of the Delta variant and the older age demographic among cruise passengers, no severe cases or fatalities were reported during the study period.

The CDC recommendations to mitigate the spread of respiratory viruses on cruise ships. These include encouraging vaccination against influenza and COVID-19 for individuals aged 6 months and older. By implementing these measures, cruise ship management can effectively reduce the risk of viral respiratory infections among passengers and crew members.2

The study has certain limitations, including the challenge of direct observation in live cruise environments and potential differences in underreporting rates across regions. Additionally, factors such as vaccination type, cabin occupancy, and onboard activities were not fully accounted for, warranting further investigation.

The findings underscore the effectiveness of masking and other NPMs in mitigating COVID-19 transmission onboard cruise ships. The study advocates for the integration of high filtration into routine case management and outbreak response strategies, emphasizing their importance in future public health emergencies. The study protocol received approval from relevant health authorities and ethics committees, ensuring adherence to ethical guidelines and protection of participants' rights.

References

  1. Mouchtouri V, Kourentis L, Anagnostopoulos L, et. al. Interventional Study of Nonpharmaceutical Measures to Prevent COVID-19 Aboard Cruise Ships. Emerging Infectious Diseases. Published May 2024. Accessed May 1, 2024. https://wwwnc.cdc.gov/eid/article/30/5/23-1364_article
  2. CDC. Guidance for Cruise Ships on Management of Acute Respiratory Illness (ARI) due to Viral Infection. Published December 23, 2023. Accessed May 1, 2025. https://www.cdc.gov/quarantine/maritime/guidance-ARI.html
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