Here’s a careful fact‑check of the 9News article you linked, against the underlying peer‑reviewed study and other reputable reporting.

Article: 9News Australia — “COVID‑19 mRNA vaccine could help people with cancer live longer, study finds” (23 Oct 2025).
Primary study: Nature — “SARS‑CoV‑2 mRNA vaccines sensitize tumours to immune checkpoint blockade” (published 22 Oct 2025; DOI: 10.1038/s41586‑025‑09655‑y). [9news.com.au] [nature.com]

1) Core claim: “mRNA COVID vaccines could help cancer patients live longer”

✅ Mostly accurate, with big caveats

The Nature paper reports that among people with advanced non‑small cell lung cancer (NSCLC) or metastatic melanoma receiving immune checkpoint inhibitors (ICIs), those who got an mRNA COVID vaccine within ~100 days of starting ICI had better overall survival than those who did not.
The key caveat: these are retrospective observational cohorts, not randomized trials—so they show association, not proof that vaccination caused longer survival. [nature.com], [sciencenews.org]

What 9News gets right: It frames the finding as something the vaccine “could” do and notes that further trials are required, which is consistent with the study’s own framing and independent commentary. [9news.com.au], [sciencenews.org]

2) Mechanism claim: “by helping the immune system fight tumours”

✅ Supported (as a plausible mechanism)

The Nature study provides mechanistic evidence (including preclinical models) suggesting that SARS‑CoV‑2 mRNA vaccines can act as potent immune stimulators, driving type‑I interferon signaling and immune activation that can sensitize ‘cold’ tumours to checkpoint blockade (ICI therapy).
MD Anderson’s research summary similarly describes the vaccines as an immune “alarm” that may reprogram immune responses in ways that can synergize with ICIs. [nature.com], [mdanderson.org] [mdanderson.org], [sciencenews.org]

Important nuance: the benefit is presented mainly as synergy with ICIs, not as the vaccine acting like a stand‑alone cancer treatment. [nature.com], [mdanderson.org]

3) The numbers: where 9News is accurate vs where it overstates

3a) “Within 100 days… lived twice as long”

⚠️ Directionally right, but “twice” is an oversimplification

For NSCLC at MD Anderson, the paper reports median overall survival of 20.6 months (unvaccinated) vs 37.3 months (vaccinated) when vaccination occurred within 100 days of ICI initiation.
That’s about 1.8× longer (37.3/20.6 ≈ 1.81)—close enough that “nearly twice” is a fair journalistic shorthand, and Science News also uses “nearly twice as long.” [nature.com] [nature.com], [sciencenews.org]

But “twice as long” is still a simplification, and it may confuse readers because the “doubling” depends on which metric you’re talking about (median survival vs 3‑year survival proportion). [nature.com], [9news.com.au]

3b) “Median survival… increased by over three years” (lung cancer)

❌ This appears incorrect

Using the Nature medians for NSCLC (37.3 vs 20.6 months), the difference is 16.7 months—about 1.4 years, not “over three years.”
It’s possible 9News conflated “three‑year survival rate” (a percentage alive at 3 years) with “survival increased by three years,” but as written, “median survival increased by over three years” does not match the paper’s reported median values. [nature.com], [9news.com.au] [nature.com], [sciencenews.org]

3c) “Skin cancer surviving up to 40 months longer”

⚠️ Not supported as stated (based on what the study reports)

For metastatic melanoma, the Nature paper reports median OS of 26.67 months in the unvaccinated group and median OS “not reached” in the vaccinated group at the time of analysis.
“Not reached” means the vaccinated group’s median survival exceeded the follow‑up threshold, but it does not directly translate to “up to 40 months longer” without additional details (follow‑up duration, survival curves, etc.).
So, the direction (vaccinated group did better) aligns with the study, but the specific “40 months longer” claim is not clearly supported by the primary result as reported in the Nature paper. [nature.com] [nature.com], [sciencenews.org] [nature.com], [9news.com.au]

4) Scope: who does this apply to?

✅/⚠️ 9News implies breadth; the evidence is narrower

The strongest evidence in the Nature paper centers on patients with NSCLC or metastatic melanoma receiving immune checkpoint inhibitors, with vaccination near the start of ICI therapy.
Science News also emphasizes this is about making some cancer treatments (immunotherapy) more effective, not about mRNA COVID vaccines generally extending life across all cancers/treatments. [nature.com], [mdanderson.org] [sciencenews.org], [nature.com]

So: it’s not “all cancer patients,” and it’s not “the vaccine fights cancer” in isolation—rather, it’s a potential adjunct effect with ICI immunotherapy that still needs prospective confirmation. [nature.com], [sciencenews.org]

5) Causality & next steps: what’s still unproven?

✅ Correctly cautious—randomized trials needed

Even though the authors report extensive statistical controls (covariates, propensity score matching, immortal time bias correction), the study remains observational, so residual confounding can’t be ruled out.
MD Anderson explicitly notes that a randomized Phase III trial is being designed to validate whether mRNA COVID vaccines should be incorporated into care for patients receiving immune checkpoint inhibition. [nature.com], [sciencenews.org] [mdanderson.org], [sciencenews.org]

6) Practical takeaway (non‑medical advice)

• The best‑supported statement is: “In retrospective cohorts, mRNA COVID vaccination around the start of checkpoint inhibitor immunotherapy was associated with better survival in advanced NSCLC and metastatic melanoma, with plausible immune‑activation mechanisms.” [nature.com], [mdanderson.org]
• The weaker / misleading part in the 9News write‑up is the quantification, especially “over three years” (lung) and “40 months longer” (skin), which don’t clearly match the paper’s reported medians. [nature.com], [9news.com.au]
• Separate from any anticancer effect, major cancer organizations still urge most people with cancer to stay up‑to‑date with COVID vaccination because cancer patients are at higher risk from COVID complications. [cancer.gov]