Long term effectiveness of inactivated vaccine BBIBP-CorV (Vero Cells) against COVID-19 associated severe and critical hospitalization in Morocco

  1. Jihane Belayachi
  2. Majdouline Obtel
  3. Rachid Razine
  4. Redouane Abouqal

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Abstract

INTRODUCTION

We provide national estimates of the real-world Vaccine effectiveness (VE) based on nationally available surveillance data. The study aimed to estimate the effectiveness of the inactivated Covid-19 vaccine BBIBP-CorV (Vero Cells) Sinopharm vaccine currently deployed in Morocco to reduce the risk of hospitalization from a severe infection of SARS- CoV-2 virus within 9 months after vaccination.

METHODS

We conducted a test-negative, case-control study among a population aged 18 years or older who were tested by rt-PCR for SARS-CoV-2 infection from February to October 2021 in Morocco. From the national laboratory COVID-19 database; we identified cases who were rt-PCR positive amongst severe and critical COVID-19 cases and controls who had a negative rt-PCR test for SARS-CoV-2. From the national vaccination register (NVR); individuals vaccinated with COVID-19 Vaccine (Vero Cell) and those unvaccinated were identified and included in the study. The linkage between databases was conducted for the study of Vaccination status based on the timing of the vaccine receipt relative to the SARS-CoV-2 rt-PCR test date. For each person, who tested positive for SARS-CoV-2, we identified a propensity score-matched control participant who was tested negative. We estimated vaccine effectiveness using conditional logistic regression.

RESULTS

Among 12884 persons who tested positive and 12885 propensity score-matched control participants, the median age was 62 years, 47.2% of whom were female. As a function of time after vaccination of second dose vaccination, vaccine effectiveness during the first month was 88% (95% CI, 84-91), 87% (95% CI: 83-90) during the second and third month, 75% (95% CI: 67-80) during the fourth month, 61% (95% CI: 54-67) during the fifth month, and 64% (95% CI: 59-69) beyond the sixth month. VE remained high and stable during the first three months in the two-age subgroup. In the fourth month, the VE in the older population aged 60 years and above (64%) was reduced by 20 points compared to VE in the younger population (84%).

CONCLUSION

A Sinopharm vaccine is highly protective against serious SARS-CoV-2 infection under real-world conditions. Protection remained high and stable during the first three months following the second dose and decreases slightly beyond the fourth month especially beyond 60 years.

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  1. ScreenIT

    SciScore for 10.1101/2022.01.25.22269822: (What is this?)

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

    Table 1: Rigor

    EthicsIRB: The study was approved by the Rabat local ethic committee review board for biomedical research at Mohammed V University (N/21).
    Consent: A waiver of informed consent was granted for the study.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Experimental Models: Cell Lines
    SentencesResources
    Study design: We estimate the real-world vaccine effectiveness (VE) over time after administration of two doses of inactivated COVID-19 vaccine BBIBP-CorV (Vero Cells) Sinopharm against COVID-19-associated severe or critical hospitalized cases using a test-negative, case- control study design comparing the odds of a positive SARS-CoV-2 test result between vaccinated and unvaccinated patients.
    Vero
    suggested: None
    Software and Algorithms
    SentencesResources
    All the analyses were conducted using Stata (version 14; StataCorp, College Station, TX, USA) and R software, (version 4.1.2; R Foundation for Statistical Computing).
    StataCorp
    suggested: (Stata, RRID:SCR_012763)

    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:
    Due to the observational study design, selection bias and confounding effects were inevitable limitations. Then, this analytical approach was implemented to reduce potential bias due to variation in the epidemic phase, gradual vaccination15 and other confounders16. The test-negative design has been used extensively to estimate VE among medically attended influenza virus illness and is believed to minimize biases associated with access to vaccines and healthcare-seeking behaviours17, and recommended by the WHO interim guidance18. In conclusion, in accordance with the results of phase III clinical trials, the licensed Sinopharm vaccine is highly protective against SARS-CoV-2 in real conditions. In addition, this study confirms the durability of the protection. VE depends not only on the effectiveness of the vaccine itself but also on factors such as the age of the recipient and time since the latest dose. This study of vaccine effectiveness focuses on the specific subset of cases - severe or critical - with the greatest burden on health systems, regardless of their level of maturity, and requires the most attention for vaccine effectiveness evaluations. The elderly population is more vulnerable and at greater risk of immune depletion overtime after full immunization and deserves special attention. Therefore, maintaining the stability of their protection, through either continued social distancing or active vaccination, must be a priority. Governments may face declining public c...

    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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  2. Version published to 10.1101/2022.01.25.22269822v1 on medRxiv