Beyond prevention: can vaccines be an ally in cancer treatment?
Have you got your flu shot this year? It probably depends on your age, your possible underlying illnesses and whether you gave it a high priority. Well in the end, some of us are vaccinated, other aren’t. It’s often a personal choice, but it raises a vital question: is it a well-informed one?
Is the vaccine vial half full or half empty?
Though a complete picture of the risks and benefits of vaccines is what one needs to decide, some people have been obsessed by their possible negative side effects. Like, could the substances composing vaccines be toxic to the body? Or could they induce some serious illnesses?
When hypotheses about side effects are investigated rigorously, they often turn out to be wrong or ‘chance associations’. In the instances where they are true, the scientific community adjusts the risk-benefit ratio accordingly. So yes, vaccines may have (negative) side effects and it is essential to document the frequency and severity of these events to inform on vaccine risk-benefit ratio. But the focus on the ‘negative’ often obscures a far more interesting story.
Who said side effects must be negative?
What’s less known, yet far more intriguing in my opinion, is that vaccines can have positive side effects. For instance, did you know that receiving a flu shot while being hospitalised for a heart failure reduced the risk of dying within the next year by 24%? Or that patients who received a flu shot soon after their hospital admission for a heart attack were 40% less likely to die within a year?
These results come from rigorous randomised clinical trials and there are strong reasons to believe this is not only due to the prevention of flu complications. Vaccines appear to modify the underlying cardiac disease in a good way. For these reasons, cardiologists worldwide have started implementing this in clinical practice.
From tuberculosis to cancer: a history of repurposing
As a medical doctor trained in public health I found these results fascinating. Existing, accessible treatments (flu vaccines here) can have a major impact beyond what they were initially developed for. It shows that innovation can come from simple ideas. It triggered my interest: could vaccines for infectious diseases offer new options in cancer treatment? After all, BCG – the tuberculosis vaccine – had been repurposed already as a treatment against bladder cancer in the 1970s.
In 2019, before COVID-19 kicked in, Anticancer Fund started to compile all data about the effect of infectious diseases vaccines on cancer. Our 2021 publication with the results revealed several ‘surprises’:
- The cholera vaccine was associated with better outcomes in prostate cancer though it could be that people getting a cholera vaccine are healthier than those who didn’t.
- Multiple skin tumours related to HPV infection vanished after a person received several injections of the vaccine used to prevent HPV infection, which is remarkable as the preventive vaccine isn’t expected to treat established HPV lesions.
We were close to launch a call for research projects on this topic to incentivise oncologists and researchers to run trials with vaccines but with our limited budget, we had to make hard choices and ultimately didn’t.
Surprising results in side effects of vaccines
Since 2021 and with the massive vaccination campaigns and scrutiny that came with COVID-19, new data emerged on possible positive side effects of vaccines in cancer patients. Some people diagnosed with cancer and treated for it happened to receive COVID-19 and flu vaccines during their treatment. Just by coincidence, many of these patients received both immunotherapy and an infectious disease vaccine in the same period.
Recently, during the main cancer conferences of 2025 (ASCO & ESMO) that we attended, results were presented about the survival of those patients. And guess what? Getting a vaccine soon after the start of immunotherapy is associated with greater survival. This is just an association and could fall into the ‘chance association’ that eventually made so many hypotheses about negative side effects untrue. But it makes sense from a biological standpoint. Vaccines are after all modulating the immune system, and given at the right time, they may ‘prime’ the body to better fight cancer and stimulate anti-cancer immunity.
The road ahead: clinical trials
I’m getting cautiously excited. To move from ‘association’ to ‘standard of care’, we must test these findings in randomized clinical trials. Several questions remain:
- Which vaccine (technology, disease, brand, adjuvant substance …) should be prioritised and used?
- Will vaccine companies collaborate or rather develop their own cancer-specific vaccines?
- And while we’re busy running multi-year clinical trials, should we test other simple ideas that could improve the efficacy of immunotherapy?
At Anticancer Fund, we believe vaccine repurposing is an interesting area for research. It represents the kind of creative thinking needed to make cancer treatments more effective and accessible.
References
https://pubmed.ncbi.nlm.nih.gov/41091650/
https://pubmed.ncbi.nlm.nih.gov/40897187/
https://pubmed.ncbi.nlm.nih.gov/40582710/
https://pubmed.ncbi.nlm.nih.gov/34459211/
https://pubmed.ncbi.nlm.nih.gov/34055652/
