Top 5 Takeaways

1. Increased Vaccine Effectiveness: A third dose of mRNA COVID-19 vaccines significantly increased vaccine effectiveness (VE) against hospitalization from 82% to 97% in immunocompetent adults and from 69% to 88% in immunocompromised adults.
2. Study Population: The study included 2,952 adults hospitalized at 21 U.S. hospitals, with a mix of COVID-19 case-patients and COVID-19–negative controls.
3. Delta Variant Period: The study was conducted during the predominance of the Delta variant, highlighting the effectiveness of the third dose during this period.
4. Public Health Implication: The findings support the recommendation for a third mRNA vaccine dose to enhance protection against COVID-19–associated hospitalization, especially in immunocompromised individuals.
5. Limitations Noted: The study acknowledged limitations such as potential confounding factors, the need for future analysis on durability of protection, and the representativeness of the study population.

Original Article Author and Citation

Corresponding Author

Mark W. Tenforde, media@cdc.gov

Suggested Citation

Tenforde MW, Patel MM, Gaglani M, et al. Effectiveness of a Third Dose of Pfizer-BioNTech and Moderna Vaccines in Preventing COVID-19 Hospitalization Among Immunocompetent and Immunocompromised Adults — United States, August–December 2021. MMWR Morb Mortal Wkly Rep 2022;71:118–124. DOI: http://dx.doi.org/10.15585/mmwr.mm7104a2

Summary

This study evaluated the effectiveness of a third dose of Pfizer-BioNTech and Moderna COVID-19 vaccines in preventing hospitalization among immunocompetent and immunocompromised adults in the United States from August to December 2021. The study found that a third dose significantly increased VE against COVID-19–associated hospitalization, particularly during the Delta variant predominance.

Methods

The study included 2,952 adults hospitalized at 21 U.S. hospitals. VE was compared between adults who received two doses and those who received a third dose of mRNA vaccines. The analysis used logistic regression to estimate VE, adjusting for factors such as age, sex, race/ethnicity, and hospital region. Patients were categorized based on their vaccination status and immunocompromising conditions.

Discussion

The findings indicate that a third dose of mRNA vaccines provides significantly higher protection against COVID-19 hospitalization compared to two doses. This underscores the importance of administering a third dose, especially for immunocompromised individuals. The study also highlights the need for ongoing evaluation of VE against emerging variants like Omicron.

Conclusion

Administering a third dose of COVID-19 mRNA vaccines enhances protection against hospitalization for both immunocompetent and immunocompromised adults. The results support current recommendations for a third dose to improve public health outcomes during the COVID-19 pandemic.

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