Top 5 Takeaways

1. High Positivity Rate: 54% of individuals tested positive for SARS-CoV-2 antigen between 5 and 9 days after symptom onset or initial diagnosis.
2. Decline Over Time: The proportion of positive antigen test results decreased as more days passed since symptom onset or initial diagnosis.
3. Impact of Vaccination and Previous Infection: Negative follow-up antigen test results were more common among those who were asymptomatic, previously infected, or vaccinated.
4. Isolation Guidance: Antigen tests may help guide isolation recommendations, especially in determining when it is safe to end isolation.
5. Mask Usage: Even if isolation ends after 5 days, continued mask use for 10 days is recommended to reduce the risk of transmission.

Original Article Author and Citation

Corresponding Author

Ian D. Plumb, iplumb@cdc.gov

Suggested Citation

Lefferts B, Blake I, Bruden D, et al. Antigen Test Positivity After COVID-19 Isolation — Yukon-Kuskokwim Delta Region, Alaska, January–February 2022. MMWR Morb Mortal Wkly Rep 2022;71:293–298. DOI: http://dx.doi.org/10.15585/mmwr.mm7108a3

Summary

This study examined the positivity rate of SARS-CoV-2 antigen tests among individuals in the Yukon-Kuskokwim Delta Region of Alaska, 5–9 days after symptom onset or initial diagnosis. It found that 54% of individuals tested positive during this period, with the proportion of positive results decreasing over time. Negative follow-up antigen tests were more likely among asymptomatic individuals, those with previous infections, and vaccinated individuals. The findings suggest that antigen tests can be useful in guiding isolation recommendations, with continued mask use recommended for 10 days post-infection.

Methods

Data were collected from 3,502 individuals with SARS-CoV-2 infections reported to the Yukon-Kuskokwim Health Corporation (YKHC) between January 1 and February 9, 2022. Follow-up antigen tests were conducted 5–9 days after symptom onset or initial positive test. Demographic data, symptom status, vaccination status, and previous infection history were recorded. Multivariable logistic regression models were used to identify factors associated with positive follow-up antigen test results.

Discussion

The study found that the majority of individuals had positive antigen test results 5–9 days after symptom onset or initial diagnosis, with the proportion of positive results declining over time. Positive results were more likely among symptomatic individuals and less likely among those with previous infections or vaccinations. The findings highlight the potential utility of antigen tests in guiding isolation recommendations, although continued mask use is essential to reduce transmission risk.

Conclusion

Antigen tests can be a valuable tool for determining the duration of isolation after SARS-CoV-2 infection. The study supports the use of antigen tests to guide isolation recommendations, with a significant proportion of individuals testing positive 5–9 days post-infection. Continued mask use for 10 days is recommended to mitigate the risk of transmission.

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