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  • rtwinOPtoCovid19💉 etc •Negative efficacy - A Case-Control Study in Japanese Small and Medium-Sized Enterprises - Published: Dec 13th, 2024
    1·
    6 days ago
    Notable comment to the published article, on their website. copied below:

    SADAO SUZUKI, MD, PhD Dec 18, 2024 at 05:34 PM

    The paper entitled, ‘Behavioral and Health Outcomes of mRNA COVID-19 Vaccination: A Case-Control Study in Japanese Small and Medium-Sized Enterprises’ written by Dr. Nakatani et al. concludes higher reported incidence of COVID-19 infection among vaccinated individuals than unvaccinated individuals. However, this study raises several concerns that cannot be overlooked.

    First, although the title of the study contains “Case-Control Study,” this is not a case-control study. ‘The case-control study starts with a group of cases, which are the individuals who have the outcome of interest. The researcher then tries to construct a second group of individuals called the controls, who are similar to the case individuals but do not have the outcome of interest’ [1]. In this study, however, the researcher first collects whole study subjects and then divides them into two groups: one with outcome and one without outcome. In this respect, the retrospective cohort approach, which divides the entire subject population by exposure, and examines outcome status by exposure group, is more natural and straightforward. Because the authors chose the framework of a case-control study, Table 1 is divided by outcome information, and an important information of the distribution of potential confounders by exposure status is not known.

    Second, the primary outcome of this study was the presence or absence of self-reported COVID-19 infection. However, the time frame of the outcome was not questioned and a longitudinal analysis could not be performed. If a subject was infected with COVID-19 before the first vaccination and then received six additional vaccinations and prevented the infection, then vaccination cannot be the cause of COVID-19 infection. In the study, however, the association would be observed between the vaccination and the infection. Without knowing the time frame of the outcome, a causal relationship cannot be discussed.

    Third, the study is inadequate in describing important information. Most importantly, all of the subjects were Yamato project participants and/or employees of SMEs, whose attributes were not described at all. Moreover, the actual questionnaire used is not shown, and the specifics of the questions are not clear. For example, we do not know what “eating habits” refers to. Throughout this paper, such descriptions are severely lacking. In addition, the data set is not publicly available.

    Fourth, the studies were derived from two different populations, but were combined without assumption. Here, we would like to point out the possibility of confounding due to the different backgrounds of the two groups, Yamato project participants and employees of SMEs. Confounding could occur if the vaccination or infection status of the two groups differs. Adjustment for the groups or confirmation of the absence of confounding is essential.

    Fifth, the study population was described by the authors as “the study team believed that the participants reasonably approximated the broader workforce of SMEs in Japan”. However, 504 of the 913 subjects (55.2%) were unvaccinated. Considering that the proportion of unvaccinated persons aged 20 years or older in Japan is 11.6% [2] (as of April 1, 2023), this is a biased population with approximately five times as many unvaccinated persons and is not representative. In this paramount matter, the “reasonable approximation” is completely false. The authors are accountable for the type of population which they chose, why the unvaccinated rate is so high, and with what intent the “reasonable approximation” statement was made.

    And last but not least, the validity of the odds ratios is not fully considered. For the odds ratio to be valid, the accuracy of COVID-19 diagnosis must be constant regardless of vaccination status. However, it is conceivable that vaccination is associated with diagnostic diligence for the disease in question, in which case there would be a difference in diagnostic accuracy, resulting in information bias. This bias increases the odds ratio without causality.

    References

    1. https://pubmed.ncbi.nlm.nih.gov/28846237/
    2. https://www.mhlw.go.jp/content/nenreikaikyubetsu-vaccination_data.pdf

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