Top 5 Takeaways

1. High Vaccine Effectiveness: Receiving 2 or 3 doses of an mRNA COVID-19 vaccine was associated with a 90% reduction in risk for COVID-19–associated invasive mechanical ventilation (IMV) or death.
2. Omicron Period Protection: During the Omicron predominance period, the protection of 3 mRNA vaccine doses was 94%.
3. Older and Immunocompromised Patients: Vaccinated patients who experienced severe outcomes were generally older and had more chronic medical conditions compared to unvaccinated patients.
4. Consistency Across Variants: The vaccine’s effectiveness against severe outcomes was consistent during the Delta and Omicron periods.
5. Public Health Recommendation: The CDC recommends that all eligible persons get vaccinated and stay up to date with COVID-19 vaccinations to prevent severe illness and death.

Original Article Author and Citation

Corresponding Author

Mark W. Tenforde, media@cdc.gov

Suggested Citation

Tenforde MW, Self WH, Gaglani M, et al. Effectiveness of mRNA Vaccination in Preventing COVID-19–Associated Invasive Mechanical Ventilation and Death — United States, March 2021–January 2022. MMWR Morb Mortal Wkly Rep 2022;71:459–465. DOI: http://dx.doi.org/10.15585/mmwr.mm7112e1

Summary

This study evaluated the effectiveness of mRNA COVID-19 vaccines in preventing the most severe outcomes of COVID-19, including invasive mechanical ventilation (IMV) and death, among adults hospitalized in the United States from March 2021 to January 2022. The findings indicate that receiving 2 or 3 doses of an mRNA vaccine significantly reduces the risk of these severe outcomes, with a 90% overall reduction in risk. The effectiveness was consistent across different variants, including Delta and Omicron.

Methods

The study used a case-control design, enrolling adults aged ≥18 years hospitalized at 21 U.S. medical centers. Case-patients were those who received IMV or died within 28 days of hospitalization, while control-patients were those hospitalized without COVID-19 or with negative SARS-CoV-2 test results. Vaccination status was verified through state registry data, hospital records, vaccination cards, and self-reports. The effectiveness of 2 or 3 doses of mRNA vaccines was calculated using logistic regression, adjusting for various demographic and clinical factors.

Discussion

The analysis found that mRNA vaccines are highly effective in preventing severe COVID-19 outcomes, including IMV and death. The protection was robust across different SARS-CoV-2 variants and was particularly high for those who received a third vaccine dose. The study also highlighted that most vaccinated patients who experienced severe outcomes were older or had complex underlying conditions, emphasizing the importance of vaccination in these populations.

Conclusion

COVID-19 mRNA vaccines provide strong protection against severe illness and death, even during periods dominated by new variants like Omicron. The findings support the CDC’s recommendation for all eligible individuals to get vaccinated and stay up to date with their COVID-19 vaccinations to prevent severe outcomes.

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