A post on X by Nicolas Hulscher claimed that "mRNA booster shots increase cancer death risk by 72% and reduce cancer survival time by 50%," framing personalized mRNA cancer vaccines as a "PHARMA SCAM." The user indicated the poster was referencing a study on repeated COVID-19 vaccination and pancreatic cancer prognosis published in the journal Cancers in 2025. That retrospective study, conducted at the Miyagi Cancer Center in Japan, examined 272 pancreatic cancer patients diagnosed between 2018 and 2023 and found that those who received three or more COVID-19 mRNA vaccinations had significantly shorter overall survival than those who received fewer shots.
The specific figures in the viral post do not match the study's findings. The study reported median overall survival of 10.3 months for the heavily vaccinated group versus 14.9 months for the less-vaccinated group — a roughly 31% difference, not the claimed 50% reduction. The study did not report any figure resembling a 72% increase in cancer death risk. Its primary measure was overall survival in pancreatic cancer patients, not cancer-specific mortality risk in the general population. The researchers also linked higher serum IgG4 levels, which increased with repeated vaccination, to poorer outcomes, but this mechanistic finding remains preliminary.
The study itself has notable limitations that the viral post ignores entirely. It was retrospective and drew on a single cancer center in Japan, where vaccination rates and booster uptake were higher than in many countries. The sample size for the key IgG4 analyses was just 96 patients, and the researchers did not control for all potential confounders, including comorbidities and vaccine type. The authors explicitly call for larger, multi-center studies to confirm the association. An observational correlation in a small cohort is not the same as a proven causal mechanism, and it is far from the sweeping claim made in the post.
The post compounds these distortions by blending two unrelated topics. The pancreatic cancer study examined COVID-19 mRNA boosters, not the Moderna-Merck personalized cancer vaccine — known as intismeran — that actually prompted the viral reaction. In that Phase 3 melanoma trial, announced in August 2026, the personalized vaccine combined with Merck's Keytruda significantly extended the time patients lived without their cancer returning, according to STAT News and CNBC. Presenting a positive clinical-trial result as evidence that cancer vaccines are dangerous requires conflating different products, different populations, and different outcomes. In sum, the viral post overstates a small observational finding, misattributes specific statistics that do not exist in the research, and conflates two distinct uses of mRNA technology, making the overall claim misleading to readers.
