Critique of "Association between maternal mRNA COVID-19 vaccination in early pregnancy and major congenital anomalies in offspring": Shared Pathway Suppression
Adjusting for influenza vaccination while studying the effects of COVID-19 injections is not a good idea.
STUDY: "Association between maternal mRNA COVID-19 vaccination in early pregnancy and major congenital anomalies in offspring." BMJ.
The study titled "Association between maternal mRNA covid-19 vaccination in early pregnancy and major congenital anomalies in offspring" is a large, population-based cohort study conducted in Ontario, Canada. It sought to determine whether maternal mRNA COVID-19 vaccination during the first trimester of pregnancy was associated with an increase in major congenital anomalies in offspring.
While this study demonstrates a commendable effort to address confounding through propensity score matching and sibling comparisons, the decision to adjust for influenza vaccination as a proxy for healthcare-seeking behavior raises significant methodological concerns that may compromise the validity of its findings.
The use of influenza vaccination as a proxy for healthcare-seeking behavior is inherently flawed. Influenza vaccination reflects only a narrow dimension of health engagement—specifically, vaccine uptake for a different illness—while failing to capture broader indicators of healthcare engagement, such as adherence to prenatal care schedules, management of chronic diseases, or maternal health literacy. Moreover, the behavioral and cultural factors influencing decisions to vaccinate against influenza differ significantly from those driving decisions to receive mRNA COVID-19 vaccines. Motivations for COVID-19 vaccination may be shaped by perceptions of novel vaccine technologies, hesitancy related to their novelty, and differing assessments of risk. Adjusting for influenza vaccination inadequately reflects these complexities, leaving residual confounding unaddressed.
Adjusting for influenza vaccination also introduces the risk of overadjustment, particularly if healthcare-seeking behavior mediates the relationship between maternal COVID-19 vaccination and neonatal outcomes. Controlling for this variable may suppress genuine pathways through which COVID-19 vaccination influences outcomes, leading to an underestimation of any potential association. Additionally, because individuals who receive influenza vaccines are likely to have also received COVID-19 vaccines, this adjustment may introduce collinearity, destabilizing model estimates and complicating interpretation. By inadvertently obscuring meaningful associations, the analysis risks masking subtle effects or potential benefits of COVID-19 vaccination.
The binary classification of "vaccinated vs. unvaccinated" oversimplifies the complexity of healthcare-seeking behavior. Within the unvaccinated group, significant heterogeneity exists, ranging from individuals who actively engage with healthcare but refuse vaccination for personal or cultural reasons to those who face systemic barriers to accessing healthcare. Similarly, vaccinated individuals may differ significantly in timing of vaccination, medical history, or socioeconomic background. By failing to account for this heterogeneity, the analysis introduces further potential for confounding that is not adequately addressed by the adjustment for influenza vaccination alone.
A more comprehensive approach to adjusting for healthcare-seeking behavior would have greatly strengthened the study’s conclusions. Incorporating variables such as frequency of prenatal visits, individual-level socioeconomic data, or indicators of chronic disease management could provide a more robust understanding of healthcare engagement. These measures would better reflect the nuanced factors influencing both vaccination uptake and pregnancy outcomes, reducing residual confounding. Stratified analyses by influenza vaccination status or the use of instrumental variable approaches, such as regional differences in vaccine availability, would also help disentangle the effects of healthcare-seeking behavior from the effects of vaccination itself.
The decision to adjust for influenza vaccination may have significant implications for the study’s findings. By relying on an inadequate proxy for healthcare-seeking behavior, the study risks obscuring meaningful associations and drawing conclusions that do not accurately reflect the underlying relationships. This methodological choice may lead to false null findings or the failure to detect subtle associations, particularly in the context of rare outcomes. While the study’s findings are presented as evidence supporting the safety of maternal COVID-19 vaccination, the limitations in the adjustment strategy call for caution in interpreting these results.
Shared Pathway Suppression: If influenza vaccination, used as a proxy for health-care seeking behavior, mediates the relationship between COVID-19 vaccination and improved neonatal outcomes, adjusting for influenza vaccination might obscure this genuine pathway. By "controlling away" part of the effect, the study risks underestimating any association.
Future research on this topic should adopt a less misleading approach to measuring and adjusting for healthcare engagement. By incorporating more comprehensive measures of prenatal care, socioeconomic factors, and health system interactions, future studies can ensure that their findings are both robust and reliable. These adjustments will allow for a more accurate assessment of the risks and benefits associated with maternal COVID-19 vaccination, providing clearer guidance for policymakers and healthcare providers.
STUDY LINK: https://bmjmedicine.bmj.com/content/3/1/e000743
Sarah C J Jorgensen, Samantha S M Drover, Deshayne B Fell, Peter C Austin, Rohan D'Souza, Astrid Guttmann, Sarah A Buchan, Sarah E Wilson, Sharifa Nasreen, Kevin A Brown, Kevin L Schwartz, Mina Tadrous, Kumanan Wilson, Jeffrey C Kwong, Linda Gough - Association between maternal mRNA covid-19 vaccination in early pregnancy and major congenital anomalies in offspring: population based cohort study with sibling matched analysis: BMJ Medicine 2024;3:e000743.
They throwing the baby out with the bathwater?
Without reading the study, I have a few comments.
One, JAMA just released a "study" trying to correlate abortion "bans" with higher infant mortality. This study should be construed as evidence of COVID 19 vaccination and infant mortality. It's impossible to trust what comes from these journals anymore. Evidence was relegated to Texas, which showed a rise in infant mortality from approx. 1900 per year to 2200 failing to mention VT, OR, and other states with marked increases and no 'abortion bans'. The study period was 2021 to 2022. VT during that time went from 0 infant deaths to 30 (I'm going by memory so it may be a bit less). Here's the study, if you want to call it that. It's more support for abortion. You just have to go to CDC wonder to find infant mortality. Talk about confounding factors being completely ignored. https://jamanetwork.com/journals/jamapediatrics/article-abstract/2819785
Two, one just needs to start looking at NICU babies to realize congenital abnormalities went up precipitously during vaccine rollout and use, which wasn't seen to this extent even WITH the flu vaccine.
Three, I raised the question of vaccinating during pregnancy with the flu vax which started in 2005 with a big push in and around 2012. We see MATERNAL deaths tick upwards and still do today, say nothing of infant mortality.
All these lives lost and no science done PRIOR to just jabbing people. It's criminal. No informed consent to these pregnant mothers either. The safety is sorely lacking and they are all (including the babies of course) one big fat experiment.