COVID-19-Associated Hospitalizations Among Vaccinated and Unvaccinated Adults 18 Years or Older in 13 US States, January 2021 to April 2022

  1. Fiona P. Havers
  2. Huong Pham
  3. Christopher A. Taylor
  4. Michael Whitaker
  5. Kadam Patel
  6. Onika Anglin
  7. Anita K. Kambhampati
  8. Jennifer Milucky
  9. Elizabeth Zell
  10. Heidi L. Moline
  11. Shua J. Chai
  12. Pam Daily Kirley
  13. Nisha B. Alden
  14. Isaac Armistead
  15. Kimberly Yousey-Hindes
  16. James Meek
  17. Kyle P. Openo
  18. Evan J. Anderson
  19. Libby Reeg
  20. Alexander Kohrman
  21. Ruth Lynfield
  22. Kathryn Como-Sabetti
  23. Elizabeth M. Davis
  24. Cory Cline
  25. Alison Muse
  26. Grant Barney
  27. Sophrena Bushey
  28. Christina B. Felsen
  29. Laurie M. Billing
  30. Eli Shiltz
  31. Melissa Sutton
  32. Nasreen Abdullah
  33. H. Keipp Talbot
  34. William Schaffner
  35. Mary Hill
  36. Andrea George
  37. Aron J. Hall
  38. Stephanie R. Bialek
  39. Neil C. Murthy
  40. Bhavini Patel Murthy
  41. Meredith McMorrow

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Abstract

Understanding risk factors for hospitalization in vaccinated persons and the association of COVID-19 vaccines with hospitalization rates is critical for public health efforts to control COVID-19.

Objective

To determine characteristics of COVID-19–associated hospitalizations among vaccinated persons and comparative hospitalization rates in unvaccinated and vaccinated persons.

Design, Setting, and Participants

From January 1, 2021, to April 30, 2022, patients 18 years or older with laboratory-confirmed SARS-CoV-2 infection were identified from more than 250 hospitals in the population-based COVID-19–Associated Hospitalization Surveillance Network. State immunization information system data were linked to cases, and the vaccination coverage data of the defined catchment population were used to compare hospitalization rates in unvaccinated and vaccinated individuals. Vaccinated and unvaccinated patient characteristics were compared in a representative sample with detailed medical record review; unweighted case counts and weighted percentages were calculated.

Exposures

Laboratory-confirmed COVID-19–associated hospitalization, defined as a positive SARS-CoV-2 test result within 14 days before or during hospitalization.

Main Outcomes and Measures

COVID-19–associated hospitalization rates among vaccinated vs unvaccinated persons and factors associated with COVID-19–associated hospitalization in vaccinated persons were assessed.

Results

Using representative data from 192 509 hospitalizations (see Table 1 for demographic information), monthly COVID-19–associated hospitalization rates ranged from 3.5 times to 17.7 times higher in unvaccinated persons than vaccinated persons regardless of booster dose status. From January to April 2022, when the Omicron variant was predominant, hospitalization rates were 10.5 times higher in unvaccinated persons and 2.5 times higher in vaccinated persons with no booster dose, respectively, compared with those who had received a booster dose. Among sampled cases, vaccinated hospitalized patients with COVID-19 were older than those who were unvaccinated (median [IQR] age, 70 [58-80] years vs 58 [46-70] years, respectively; P  < .001) and more likely to have 3 or more underlying medical conditions (1926 [77.8%] vs 4124 [51.6%], respectively; P  < .001).

Conclusions and Relevance

In this cross-sectional study of US adults hospitalized with COVID-19, unvaccinated adults were more likely to be hospitalized compared with vaccinated adults; hospitalization rates were lowest in those who had received a booster dose. Hospitalized vaccinated persons were older and more likely to have 3 or more underlying medical conditions and be long-term care facility residents compared with hospitalized unvaccinated persons. The study results suggest that clinicians and public health practitioners should continue to promote vaccination with all recommended doses for eligible persons.

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  1. Version published to 10.1001/jamainternmed.2022.4299
  2. ScreenIT

    SciScore for 10.1101/2021.08.27.21262356: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Ethicsnot detected.
    Sex as a biological variablenot detected.
    RandomizationTo select sampled cases, random numbers are generated and assigned to each case.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    All analyses were conducted using SAS 9.4 software (SAS Institute Inc.
    SAS
    suggested: (SASqPCR, RRID:SCR_003056)
    SAS Institute
    suggested: (Statistical Analysis System, RRID:SCR_008567)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    This analysis has several limitations. Although COVID-NET covers approximately 10% of the U.S. population, our findings may not be generalizable to the entire country. Since SARS-CoV-2 testing was conducted at the discretion of healthcare professionals, COVID-NET may not have captured all COVID-19-associated hospitalizations. The primary reason for hospital admission was not always clear, and some patients who met the COVID-NET case definition may have been hospitalized for reasons that were not primarily related to COVID-19. The inclusion of these hospitalizations in rate calculations could have resulted in an overestimation of hospitalization rates for COVID-19 for both unvaccinated and vaccinated persons. Using population-based hospitalization rates, our study found unvaccinated adults are hospitalized at rates that are 17 times higher than for vaccinated adults in the same catchment areas. Rates of COVID-19-associated hospitalizations are far higher in unvaccinated persons in all adult age groups, even during a period when the highly-transmissible Delta variant was the predominant circulating variant.12 Population-based hospitalization rates will be a critical metric in the continued assessment of the effectiveness of vaccines in the population, and complementary to vaccine effectiveness studies using other methods.4,18 The much higher rates observed in unvaccinated persons compared to vaccinated adults suggest that vaccines remain highly effective in preventing hospitali...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

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  3. Version published to 10.1101/2021.08.27.21262356v1 on medRxiv