What are reported causes of death and excess mortality linked to Pfizer or Moderna compared with Sinovac in peer-reviewed studies?

1. What the key peer‑reviewed claims say about Pfizer vs. Moderna — an unexpected mortality gap

A linked-records study of Milwaukee County adults concludes that, for two-dose vaccinees aged 60+, mortality after Pfizer vaccination was approximately 248% of that after Moderna over April 2021–June 2022, a gap that narrowed and lost statistical significance after booster doses; the authors hypothesize Moderna’s larger antigen dose may explain the older-age advantage ^{[1] [4] [5]}. This claim rests on administrative linkage of vaccination and mortality records, and the study frames the result as consistent across that population and time window. The study does not compare either mRNA product directly to Sinovac, so its relevance to Pfizer‑/Moderna‑versus‑Sinovac mortality comparisons is indirect and limited ^{[1] [4]}.

2. Autopsy and medicolegal evidence: cardiac and thrombotic causes appear frequently in post‑vaccination death reviews

A systematic autopsy review reports that among 325 adjudicated post‑vaccination autopsy cases, approximately 74% were judged directly due to or significantly contributed to by vaccination, with predominant causes including sudden cardiac death, pulmonary embolism, myocardial infarction, and myocarditis; the review treats these findings as potential signals but does not parse vaccine brands against each other ^[2]. National medicolegal autopsy work from Finland links myocarditis/pericarditis primarily to mRNA vaccines, especially in young men, though fatal outcomes were uncommon in that dataset; this analysis emphasizes the rarity of lethal cases and the diagnostic value of autopsy in attributing causality ^[6]. A VAERS‑based study correlates cardiac and diabetic comorbidities with reported deaths and notes many reports include breakthrough infection, underscoring complexities in attributing cause ^[7].

3. Studies that include Sinovac focus on effectiveness, not fatal adverse events

Observational effectiveness studies comparing BNT162b2 (Pfizer) and CoronaVac (Sinovac) during Omicron BA.2 in older adults found both vaccines substantially reduced COVID‑19 mortality, with two‑dose effectiveness higher for Pfizer in some age strata but third doses bringing both to very high protection against death (for age 65+ two‑dose effectiveness ~90.7% Pfizer vs 74.8% CoronaVac; three doses raised effectiveness to >95% for both) ^{[3] [8]}. A Pakistan cohort reported no significant difference in hospitalization or mortality between mRNA and inactivated vaccines, while noting potentially faster recovery after mRNA vaccination ^[9]. These papers address COVID‑19–attributable mortality prevented by vaccines rather than deaths caused by vaccines.

4. Reconciling apparently conflicting signals: different methods, different questions

The datasets answer distinct questions: the Milwaukee linked‑records study estimates all‑cause mortality differences by vaccine brand in a U.S. county population ^[1], autopsy reviews examine pathologic causes in selected post‑vaccination deaths ^{[2] [6]}, and effectiveness studies quantify mortality prevented from COVID‑19 for different products ^{[3] [8] [9]}. These methodological distinctions explain much of the apparent conflict: an observed brand gap in all‑cause mortality does not equate to proven vaccine causation, and autopsy case series are subject to selection bias toward deaths that warranted post‑mortem study ^{[1] [2] [6]}. Effectiveness studies show comparative benefit against COVID‑19 death but do not measure vaccine‑caused excess mortality directly ^{[3] [8]}.

5. What is missing and why definitive Pfizer/Moderna vs. Sinovac mortality comparisons remain elusive

No single peer‑reviewed study in the provided material directly compares causes of death or excess all‑cause mortality for Pfizer/Moderna versus Sinovac using the same population, timeframe, and adjudication methods. The autopsy review and medicolegal studies lack brand‑comparative denominators ^{[2] [6]}, the VAERS analysis faces reporting and attribution limitations ^[7], and vaccine‑effectiveness work measures prevented COVID‑19 deaths rather than vaccine‑associated fatalities ^{[3] [8] [9]}. Heterogeneous designs, differential surveillance, age and comorbidity structure, and booster uptake are key confounders that prevent straightforward cross‑product mortality attribution ^{[1] [3]}.

6. Bottom line: limited head‑to‑head evidence, clear research priorities

The evidence shows a reported higher all‑cause mortality after two Pfizer doses compared with Moderna in older adults in one linked‑record study, multiple autopsy series identify cardiac and thrombotic causes among selected post‑vaccine deaths, and effectiveness studies show both mRNA and inactivated vaccines substantially reduce COVID‑19 mortality. However, peer‑reviewed, population‑level head‑to‑head analyses of vaccine‑attributed causes of death and excess mortality comparing Pfizer/Moderna directly with Sinovac are absent in the provided materials. Priority research needs include standardized, population‑level linkage with cause‑of‑death adjudication across vaccine brands, stratification by age/comorbidity/booster status, and transparent autopsy series with brand denominators to permit definitive comparisons ^{[1] [2] [3]}.