The effectiveness of COVID-19 vaccines in reducing the incidence, hospitalization, and mortality from COVID-19: A systematic review and meta-analysis

  1. Kazem Rahmani
  2. Rasoul Shavaleh
  3. Mahtab Forouhi
  4. Hamideh Feiz Disfani
  5. Mostafa Kamandi
  6. Rozita Khatamian Oskooi
  7. Molood Foogerdi
  8. Moslem Soltani
  9. Maryam Rahchamani
  10. Mohammad Mohaddespour
  11. Mostafa Dianatinasab

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Abstract

Vaccination, one of the most important and effective ways of preventing infectious diseases, has recently been used to control the COVID-19 pandemic. The present meta-analysis study aimed to evaluate the effectiveness of COVID-19 vaccines in reducing the incidence, hospitalization, and mortality from COVID-19.

Methods

A systematic search was performed independently in Scopus, PubMed via Medline, ProQuest, and Google Scholar electronic databases as well as preprint servers using the keywords under study. We used random-effect models and the heterogeneity of the studies was assessed using I 2 and χ 2 statistics. In addition, the Pooled Vaccine Effectiveness (PVE) obtained from the studies was calculated by converting based on the type of outcome.

Results

A total of 54 studies were included in this meta-analysis. The PVE against SARS-COV 2 infection were 71% [odds ratio (OR) = 0.29, 95% confidence intervals (CI): 0.23–0.36] in the first dose and 87% (OR = 0.13, 95% CI: 0.08–0.21) in the second dose. The PVE for preventing hospitalization due to COVID-19 infection was 73% (OR = 0.27, 95% CI: 0.18–0.41) in the first dose and 89% (OR = 0.11, 95% CI: 0.07–0.17) in the second dose. With regard to the type of vaccine, mRNA-1273 and combined studies in the first dose and ChAdOx1 and mRNA-1273 in the second dose had the highest effectiveness in preventing infection. Regarding the COVID-19-related mortality, PVE was 68% (HR = 0.32, 95% CI: 0.23–0.45) in the first dose and 92% (HR = 0.08, 95% CI: 0.02–0.29) in the second dose.

Conclusion

The results of this meta-analysis indicated that vaccination against COVID-19 with BNT162b2 mRNA, mRNA-1273, and ChAdOx1, and also their combination, was associated with a favorable effectiveness against SARS-CoV2 incidence rate, hospitalization, and mortality rate in the first and second doses in different populations. We suggest that to prevent the severe form of the disease in the future, and, in particular, in the coming epidemic picks, vaccination could be the best strategy to prevent the severe form of the disease.

Systematic review registration

PROSPERO International Prospective Register of Systematic Reviews: http://www.crd.york.ac.uk/PROSPERO/ , identifier [CRD42021289937].

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  1. Version published to 10.3389/fpubh.2022.873596
  2. ScreenIT

    SciScore for 10.1101/2021.11.03.21265819: (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.
    Randomizationnot detected.
    BlindingThe search was done blindly and independently by two researchers (K Rahmani & R Shavale) using the following keywords in the abovementioned databases: COVID-19; SARS-COV-2; coronavirus; vaccine; post-vaccination; mortality; hospitalization; readmission; reinfection; morbidity; and Breakthrough infections.
    Power Analysisnot detected.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    Search Strategy: A systematic search of PubMed, Scopus, ProQuest, and Google Scholar databases as well as the Preprint servers including medRxiv and Research Square was done to identify the studies related to the keywords studied based on the Medical Subject Headings (MeSH) published until October 15, 2021, with full texts in English, without any spacial restrictions.
    PubMed
    suggested: (PubMed, RRID:SCR_004846)
    ProQuest
    suggested: (ProQuest, RRID:SCR_006093)
    Google Scholar
    suggested: (Google Scholar, RRID:SCR_008878)
    MeSH
    suggested: (MeSH, RRID:SCR_004750)

    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:
    Despite the important results found out on the effectiveness of COVID-19 vaccines against the incidence of infection, hospitalization, and mortality after vaccination, the present study had a number of limitations, including the possibility of vaccination of specific age or occupational groups (health care worker) associated with an increase or decrease in the chance of contracting SARS-COV2 infection. However, the confounding effect of the background variables was somewhat controlled through the use of HR adjusted studies. Herd immunity was another issue that could distort the overall results; i.e. with increasing follow-ups, the risk of infection in the community and non-vaccinated people would gradually decrease, and this would overestimate the effectiveness of various COVID-19 vaccines.

    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.

  3. Version published to 10.1101/2021.11.03.21265819v1 on medRxiv