Top 5 Takeaways

1. FDA Authorization: The FDA authorized an additional dose of Pfizer-BioNTech and Moderna vaccines for immunocompromised individuals and later for those aged ≥65 years, at high risk, or with high exposure risk.
2. V-safe Monitoring: The CDC’s v-safe platform was updated to track adverse reactions to additional doses, with 22,191 registrants reporting during the study period.
3. Adverse Reactions: Most reported adverse reactions were mild to moderate, with local reactions slightly more common and systemic reactions slightly less common after the third dose compared to the second.
4. Demographics: The majority of additional dose recipients were female, and age distribution was roughly equal among three age groups: 18–49, 50–64, and 65–74 years.
5. Health Impacts: About 31.8% reported health impacts, with 28.3% unable to perform normal daily activities, and 1.8% seeking medical care.

Original Article Author and Citation

Corresponding Author

Anne M. Hause, eocevent416@cdc.gov

Suggested Citation

Hause AM, Baggs J, Gee J, et al. Safety Monitoring of an Additional Dose of COVID-19 Vaccine — United States, August 12–September 19, 2021. MMWR Morb Mortal Wkly Rep 2021;70:1379–1384. DOI: http://dx.doi.org/10.15585/mmwr.mm7039e4

Summary

Following FDA amendments to EUAs for COVID-19 vaccines, the CDC monitored adverse reactions to additional doses using the v-safe system. Data from 22,191 registrants indicated that adverse reactions were consistent with those observed after the primary series, with no unexpected patterns. Most reactions were mild to moderate, and the majority of recipients received the same vaccine brand for all doses.

Methods

The study utilized data from the v-safe platform, a voluntary, smartphone-based safety surveillance system. Registrants reported adverse reactions and health impacts during days 0–7 post-vaccination. Data analysis excluded those with mixed vaccine brands or unknown manufacturers. SAS software was used for statistical analysis.

Discussion

Initial findings from v-safe data align with clinical trial results, showing similar adverse reaction profiles between the second and third doses. The study highlighted the need for continued monitoring and additional data on mixed vaccine regimens and varying intervals between doses to inform public health recommendations.

Conclusion

The safety profile of additional COVID-19 vaccine doses appears consistent with earlier doses, with most reactions being mild to moderate. Ongoing surveillance and further research are essential to guide future vaccination strategies and recommendations.

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