Necessity of COVID-19 Vaccination in Persons who have Already had COVID-19

  1. Nabin K. Shrestha
  2. Patrick C. Burke
  3. Amy S. Nowacki
  4. Paul Terpeluk
  5. Steven M. Gordon

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Abstract

Background

The purpose of this study was to evaluate the necessity of COVID-19 vaccination in persons with prior COVID-19.

Methods

Employees of Cleveland Clinic working in Ohio on Dec 16, 2020, the day COVID-19 vaccination was started, were included. Anyone who tested positive for COVID-19 at least once before the study start date was considered previously infected. One was considered vaccinated 14 days after receipt of the second dose of a COVID-19 mRNA vaccine. The cumulative incidence of COVID-19, symptomatic COVID-19, and hospitalizations for COVID-19, were examined over the next 10.5 months.

Results

Among the 52238 employees, 4718 (9%) had prior COVID-19 at the start of the study, and 35113 (67%) had received at least two doses of the vaccine by the end of the study. Of the 4284 COVID-19 infections during the study, 3476 (81.1%) occurred in persons who were unvaccinated, and 4263 (99.5%) occurred among those without prior COVID-19. In Cox proportional hazards regression, both prior COVID-19 and vaccination were independently associated with significantly lower risk of COVID-19. Vaccination was associated with lower risk of COVID-19 among those without prior COVID-19 (HR 0.24, 95% CI 0.22–0.26) but not among those with prior COVID-19 (HR 0.86, 95% CI 0.33–2.29).

Conclusions

Both previous infection and vaccination provide substantial protection against COVID-19. Vaccination reduces risk of COVID-19 among those without prior COVID-19 but not among those with prior COVID-19, at least not within one year following infection.

Summary

Cumulative incidence of COVID-19 over 10.5 months, including the Delta phase, was examined among 52238 employees at Cleveland Clinic. Vaccination was associated with significantly lower risk of COVID-19 among those without prior COVID-19 but not among those with prior COVID-19.

Article activity feed

  1. Version published to 10.1101/2021.06.01.21258176v4 on medRxiv
  4. Version published to 10.1093/cid/ciac022
  5. Version published to 10.1101/2021.06.01.21258176v3 on medRxiv
  6. ScreenIT

    SciScore for 10.1101/2021.06.01.21258176: (What is this?)

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

    Table 1: Rigor

    EthicsIRB: The study was approved by the Cleveland Clinic Institutional Review Board.
    Consent: A waiver of informed consent and waiver of HIPAA authorization were approved to allow access to personal health information by the research team, with the understanding that sharing or releasing identifiable data to anyone other than the study team was not permitted without additional IRB approval.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: Thank you for sharing your data.

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    The study has its limitations. Because we did not have a policy of asymptomatic employee screening, previously infected subjects who remained asymptomatic might have been misclassified as previously uninfected. Given this limitation, one should be cautious about drawing conclusions about the protective effect of prior asymptomatic SARS-CoV-2 infection. It should be noted though, that 12% of the subjects classified as previously infected did not have a symptom onset date recorded, suggesting that at least some of those classified as previously infected might have been asymptomatic infections. It is reassuring that none of these possibly asymptomatically infected individuals developed COVID-19 during the duration of the study. The study follow-up duration was short, being only five months, but this was longer than published mRNA vaccine efficacy studies [1,2], and longer than the follow-up duration of the largest published vaccine effectiveness studies to date [3,4]. Median freedom from reinfection (time from initial infection until end of follow-up) in this study, for those previously infected, of almost 10 months, is consistent with findings in an earlier study that immunoglobulin G (IgG) to the spike protein remained stable over more than six months after an episode of infection [16]. Our study included no children and few elderly subjects, and the majority would not have been immunosuppressed. Data governance policies in our institution precluded us from obtaining detailed ...

    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.
    • No funding statement was detected.
    • 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.

  7. Version published to 10.1101/2021.06.01.21258176v2 on medRxiv
  8. Version published to 10.1101/2021.06.01.21258176v1 on medRxiv