Which peer-reviewed studies compare age-adjusted post-vaccination death rates across multiple countries?

1. What the literature you supplied actually contains: effectiveness and mortality signals

The New England Journal of Medicine review cites a VEBIS‑EHR network study that measured monovalent XBB.1.5 vaccine effectiveness against hospitalisations and deaths across seven European countries, indicating multi‑country analyses do exist but they focus on vaccine effectiveness with death as an outcome rather than explicit age‑adjusted post‑vaccination death‑rate comparisons across countries ^[1]. Large observational cohort work in single populations — for example, a U.S. veterans study reporting a large mortality reduction associated with the 2024–2025 vaccine in veterans — shows robust within‑country mortality analyses but does not compare age‑adjusted death rates across nations ^[2].

2. Direct cross‑country, age‑adjusted post‑vaccination death‑rate studies: not prominent in supplied sources

None of the provided items presents a clear, peer‑reviewed study that directly compares age‑adjusted post‑vaccination death rates across multiple countries in the specific way your query frames it. The medRxiv Austria study analyzes age‑stratified all‑cause mortality and post‑pandemic patterns domestically and computes hypothetical number‑needed‑to‑vaccinate estimates, but it is a single‑country preprint and does not run cross‑national age‑adjusted death‑rate comparisons ^[3]. The supplied VEBIS‑EHR work covers deaths across several European countries but is framed as vaccine‑effectiveness research, not a systematic age‑adjusted mortality‑rate comparison across nations ^[1].

3. Why multi‑country age‑adjusted death comparisons are methodologically challenging

Comparing age‑adjusted post‑vaccination death rates across countries requires harmonized death certification, consistent vaccine‑exposure ascertainment, comparable follow‑up windows, and uniform age‑standardization methods. The WHO’s guidance and data priorities for vaccine composition deliberations underscore the complexity of cross‑jurisdictional VE and outcome measurement and call for standardized underlying rates to be provided with VE estimates ^[4]. Where studies include multiple countries ^[1], they typically harmonize electronic health record inputs and focus on VE estimates rather than producing stand‑alone age‑adjusted mortality‑rate tables for public consumption ^[1].

4. Single‑country studies that are often cited instead — and their limits

Several supplied sources show strong national analyses that are sometimes invoked in cross‑national debates. The U.S. veterans cohort reported a substantial reduction in death risk after the 2024–2025 vaccine among veterans, a within‑country effect that cannot be extrapolated to international comparisons without careful adjustment ^[2]. Austria’s medRxiv paper examines pre‑versus post‑pandemic mortality patterns by 10‑year age groups and estimates NNVs for age bands, illustrating the kind of age‑stratified analysis needed — but again, it is Austrian and not peer‑reviewed at the time of posting ^[3].

5. Competing narratives in the media and retractions complicate the field

Public discourse includes claims of vaccine‑related increases in deaths or cancer that have been challenged or retracted; for example, reporting highlights a retracted Japanese study and critical analysis arguing vaccinated cohorts showed lower all‑cause death in some datasets ^[5]. Journalists and scientists cited in other pieces stress that high‑quality studies have not demonstrated a widespread vaccine‑related mortality signal, while some commentators and isolated preprints or non‑peer‑reviewed pieces continue to raise concerns ^{[6] [5]}. This mix of peer‑reviewed VE studies, preprints, and contested media claims underscores the need to rely on harmonized, peer‑reviewed, multi‑database analyses for cross‑country mortality comparisons.

6. Practical next steps if you want a definitive list of studies

Available sources do not list peer‑reviewed, multi‑country studies that present direct age‑adjusted post‑vaccination death‑rate comparisons in the narrow sense you asked. To build that list you should seek: (a) multi‑country EHR or registry consortia papers (like VEBIS‑EHR) and examine supplemental materials for age‑standardized mortality tables ^[1]; (b) national age‑stratified mortality analyses (use these for meta‑analysis) such as the U.S. veterans study or Austria’s preprint for methodology templates ^{[2] [3]}; and (c) WHO guidance on standardized metrics to ensure comparability across datasets ^[4].

Limitations: the supplied search results do not include a clear, peer‑reviewed paper that fits your exact request; many multi‑country papers focus on VE with death as an endpoint rather than explicit country‑to‑country age‑adjusted death‑rate comparisons ^{[1] [2] [3]}.