Top 5 Takeaways

1. Vaccine Effectiveness: The study found a potential decline in vaccine protection against confirmed SARS-CoV-2 infection but continued strong protection against COVID-19–associated hospitalization and death.
2. Impact of Delta Variant: As the Delta variant became predominant, the incidence rate ratios (IRRs) for cases, hospitalizations, and deaths among not fully vaccinated persons compared to fully vaccinated persons decreased.
3. Higher Rates Among Unvaccinated: COVID-19 cases, hospitalizations, and deaths were substantially higher in persons not fully vaccinated compared to those fully vaccinated.
4. Age-Related Trends: Higher hospitalization and death rates were observed in older age groups, regardless of vaccination status, with larger declines in IRRs for hospitalization and death among persons aged ≥65 years.
5. Monitoring Indicators: The study highlights the use of percentage of vaccinated persons among cases (PVC) and IRRs as indicators to monitor vaccine breakthrough cases and severe outcomes.

Original Article Author and Citation

Corresponding Author

Heather Scobie, hscobie@cdc.gov

Suggested Citation

Scobie HM, Johnson AG, Suthar AB, et al. Monitoring Incidence of COVID-19 Cases, Hospitalizations, and Deaths, by Vaccination Status — 13 U.S. Jurisdictions, April 4–July 17, 2021. MMWR Morb Mortal Wkly Rep 2021;70:1284–1290. DOI: http://dx.doi.org/10.15585/mmwr.mm7037e1

Summary

This study monitored COVID-19 cases, hospitalizations, and deaths by vaccination status across 13 U.S. jurisdictions from April 4 to July 17, 2021. It found that while vaccine protection against confirmed SARS-CoV-2 infection might have declined, vaccines continued to offer strong protection against severe outcomes such as hospitalization and death. The study also observed that the incidence rates of COVID-19 cases, hospitalizations, and deaths were significantly higher among persons not fully vaccinated compared to those fully vaccinated, particularly as the Delta variant became predominant.

Methods

Data on COVID-19 cases, hospitalizations, and deaths among persons aged ≥18 years were collected from 13 U.S. jurisdictions. The study analyzed these data by vaccination status, using age-standardized incidence rate ratios (IRRs) to compare outcomes between fully vaccinated and not fully vaccinated persons. The study periods were divided based on the prevalence of the Delta variant, with two periods: April 4–June 19 (<50% Delta variant) and June 20–July 17 (≥50% Delta variant). Statistical analyses were conducted using SAS and R software.

Discussion

The findings indicate that COVID-19 vaccines remain highly effective in preventing severe outcomes, even with the emergence of the Delta variant. However, the study noted a potential decline in vaccine effectiveness against infection. The IRRs for cases decreased more significantly than those for hospitalizations and deaths, suggesting that vaccines continue to protect well against severe disease. The study also highlighted the importance of monitoring COVID-19 outcomes by vaccination status to detect changes in vaccine effectiveness and guide public health strategies.

Conclusion

Vaccination remains a critical tool in protecting against severe COVID-19 outcomes. The study underscores the need for ongoing surveillance of COVID-19 cases, hospitalizations, and deaths by vaccination status to identify any changes in vaccine effectiveness, particularly with the emergence of new variants. Public health efforts should continue to focus on increasing vaccination coverage to mitigate the impact of COVID-19.

This has been your booster shot of MMWR Info! Please check back for more MMWR, Public Health, and Programming Tutorial content daily.