Johns Hopkins researchers tested a vaccine targeting KRAS mutations in 20 high-risk pancreatic cancer patients and found it safe, triggered immune responses in 90% of participants, and prevented cancer development over 16.5 months median follow-up. This is phase 1 trial data — early but encouraging — and some existing precancerous lesions actually shrank or stabilized rather than progressing. The missing context is that phase 1 involves a small, carefully selected population, and larger phase 2/3 trials would be needed to confirm efficacy before this becomes available as a preventive treatment.