Effectiveness of a SARS-CoV-2 mRNA vaccine booster dose for prevention of infection, hospitalization or death in two nation-wide nursing home systems

  1. Kevin W. McConeghy
  2. Barbara Bardenheier
  3. Andrew W. Huang
  4. Elizabeth M. White
  5. Richard A. Feifer
  6. Carolyn Blackman
  7. Christopher M. Santostefano
  8. Yoojin Lee
  9. Frank DeVone
  10. Christopher W. Halladay
  11. James L. Rudolph
  12. Andrew R. Zullo
  13. Vincent Mor
  14. Stefan Gravenstein

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Abstract

Background

A SARS-CoV-2 vaccine booster dose has been recommended for all nursing home residents. However, we lack effectiveness data on boosters preventing infection, death and hospitalization in this frail population.

Methods

We emulated nested target trials in two large nursing home systems in parallel to evaluate the effectiveness of a SARS-CoV-2 mRNA vaccine booster at preventing infection, hospitalization, or death. Residents who completed a 2-dose series of the mRNA vaccine and were eligible for a booster were included in from September 22, 2021 to November 5, 2021. Outcomes were measured through December 18, 2021, including test-confirmed SARS-CoV-2 infection, hospitalization, or death. The vaccine effectiveness at day 42 was estimated with a Kaplan-Meier estimator, both unadjusted and weighted with the inverse probability of treatment.

Results

The two NH systems were large and multi-state, System 1 included 200 NH (8,538 control and 5,721 boosted residents) and System 2 included 127 NHs (4,100 control and 2,291 boosted residents). Booster vaccination reduced infections by 50.4% (95% Confidence Interval [CI]: 29.4%, 64.7%) SARS-CoV-2 infections in System 1 and 58.2% (32.3%, 77.8%) in System 2. Boosted residents in System 1 also had a 97.3% (86.9%, 100.0%) reduction in SARS-CoV-2 associated death, but too few events for comparison in System 2.

Conclusions

During a Delta predominant period, SARS-CoV-2 booster vaccination significantly reduced infection in two U.S. nursing home systems. In the larger System 1 a 97% reduction in SARS-CoV-2 related death was also observed. These findings strongly support administration of vaccine boosters to nursing home residents.

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  1. ScreenIT

    SciScore for 10.1101/2022.01.25.22269843: (What is this?)

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

    Table 1: Rigor

    EthicsIRB: This study was deemed to be exempt by the Brown University institutional review board (IRB) and the VA data was approved by the Providence VA Medical Center IRB.
    Sex as a biological variablenot detected.
    RandomizationWe randomly selected one eligible target trial date per control resident.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    The first system included 200 nursing homes in 19 states with a heavy concentration in the northeast region operated by Genesis HealthCare (System 1).
    Genesis HealthCare
    suggested: None
    (Cary, NC) and STATA version 16 (Statacorp, TX).
    STATA
    suggested: (Stata, RRID:SCR_012763)
    Statacorp
    suggested: None

    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:
    Our study includes several significant limitations. To identify treatment effects, we assumed no unmeasured confounding and correct specification of probability weights in the Kaplan-Meier estimator. The relatively small differences between groups are encouraging and may arise from subjects’ eligibility requirement for prior primary series vaccination, resulting in greater cohort homogeneity. Additionally, the plots of our cumulative incidence curves for infection show close overlap in the first 7-10 days for groups. This suggests that we face relatively low risk of residual confounding if the two groups have similar baseline event risk in the window after vaccination but prior to the quickly developing post-booster immunity. A significant limitation that we do not account for is interference, or the assumption that one resident’s vaccination does not impact the effectiveness of vaccination for other residents. Subsequent work which accounts for this could lead to significantly different estimates as increasing proportions of boosted residents and staff protect unboosted residents from infection within a facility. Treatment effects assuming no interference likely underestimate the total causal effect. Additionally, deaths in the nursing home are easily identified, but for residents who are transferred, they may die after they are lost to follow-up, in which case we cannot account for them in our data. This study reports a substantial reduction in risk of SARS-CoV-2 infection ...

    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

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  2. Version published to 10.1101/2022.01.25.22269843v1 on medRxiv