Top 5 Takeaways

1. Mask Use Reduces Transmission: Close contacts with any unmasked exposure had significantly higher odds of receiving a positive SARS-CoV-2 test result compared to those with only masked exposure.
2. Impact of Multiple Exposures: Any additional exposure increased the odds of a positive test result by 40%, highlighting the importance of minimizing close contact encounters.
3. Modified Quarantine Protocol: Saint Louis University implemented a protocol considering mask use when determining quarantine needs, potentially reducing unnecessary quarantines for masked contacts.
4. Testing and Isolation: Testing 5–7 days post-exposure and immediate isolation upon positive results are crucial to prevent secondary transmission, even for masked contacts.
5. Study Limitations: Self-reported data, limited vaccination status, and pre-Delta variant conditions are notable limitations affecting the study’s findings.

Original Article Author and Citation

Corresponding Author

Terri Rebmann, terri.rebmann@slu.edu

Suggested Citation

Rebmann T, Loux TM, Arnold LD, Charney R, Horton D, Gomel A. SARS-CoV-2 Transmission to Masked and Unmasked Close Contacts of University Students with COVID-19 — St. Louis, Missouri, January–May 2021. MMWR Morb Mortal Wkly Rep 2021;70:1245–1248. DOI: http://dx.doi.org/10.15585/mmwr.mm7036a3

Summary

This study assessed the impact of mask use on SARS-CoV-2 transmission among close contacts of university students at Saint Louis University (SLU) during January–May 2021. The findings indicated that close contacts with any unmasked exposure had significantly higher odds of testing positive for SARS-CoV-2 compared to those with only masked exposure. The study supports the effectiveness of universal masking and fewer close contact encounters in preventing virus spread in university settings.

Methods

SLU implemented a modified quarantine protocol considering mask use for determining quarantine needs. Contact tracing identified close contacts of COVID-19 positive students, and mask use during exposure incidents was recorded. All close contacts underwent RT-PCR testing 5–7 days post-exposure. Statistical analyses were conducted to compare positive test rates among masked and unmasked exposures, adjusting for the number of exposure incidents.

Discussion

The study found that unmasked exposures significantly increased the odds of SARS-CoV-2 transmission. Multiple exposures further increased transmission risk. The modified quarantine protocol allowed some masked contacts to avoid quarantine, which could be beneficial in reducing missed academic activities and psychosocial impacts. However, the study’s limitations, including self-reported data and pre-Delta variant conditions, should be considered when interpreting the findings.

Conclusion

Universal masking and minimizing close contact encounters are effective strategies to reduce SARS-CoV-2 transmission in university settings. Universities may consider mask use when determining quarantine needs for unvaccinated close contacts, provided that robust testing protocols are in place. The study reinforces CDC recommendations for universal masking in indoor spaces and COVID-19 vaccination for individuals aged 12 and older.

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