Covid vaccines may have a tantalizing benefit that has nothing to do with the virus they are designed to protect against: boosting the immune system to better fight tumors during cancer treatment.
This is revealed by new results presented on Sunday in Berlin at the conference of the European Society of Medical Oncology. The research is still in its early stages – it has not yet been tested in a phase 3 clinical trial – but experts say it is promising.
“I’m cautiously optimistic,” said Stephanie Dougan, an associate professor of cancer immunology and virology at the Dana-Farber Cancer Institute, who was not involved in the work. “There is scientific logic to why this might work.”
Researchers found that among cancer patients receiving immunotherapy, those who received an mRNA Covid vaccine within 100 days before starting their treatment lived longer.
Only about 20% of cancer patients who receive immunotherapy – which harnesses a person’s immune system to fight cancer cells – respond to the treatment. Finding a way to increase the effectiveness of immunotherapy drugs is a feat that researchers have been exploring for years, without much success.
Typically, immune boosting tactics used in the past have either done too little to activate the immune system or have done too much, triggering an overactive response that can damage the body. It is possible that Covid mRNA vaccines exist in a Goldilocks zone.
“Maybe we just needed something moderately strong, and this could potentially be it,” said Dougan, who stressed the need for further research.
That research will soon be underway: Dr. Adam Grippin, a senior resident in radiation oncology at the University of Texas MD Anderson Cancer Center who co-led the study, said his team is launching a phase 3 clinical trial to confirm the initial results.
In the research presented Sunday, Grippin and his co-authors looked at the survival rates of more than 1,000 people with advanced non-small cell lung cancer who received immunotherapy as part of their treatment from 2019 to 2023. Of those, 180 people received a Covid mRNA vaccine within 100 days of starting treatment.
The median survival of the group – while exactly half of those who underwent treatment are still alive – was almost twice as long for those who were vaccinated as for those who were not: about three years compared to just over a year and a half.
The researchers also compared the survival rates of a smaller group of patients receiving immunotherapy for metastatic melanoma. Forty-three received an mRNA Covid vaccine; 167 did not. For those who were not vaccinated, the median survival was just over two years. Those who had been vaccinated before treatment had not yet reached their median survival point more than three years after follow-up.
In further experiments on mice, the researchers got a response that they say is consistent with how vaccines work in humans.
“This stimulates the immune system against tumors,” Grippin said.
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Vaccines using mRNA are already a promising area of cancer research. Scientists have developed personalized mRNA cancer vaccines, tailored to fight a person’s unique tumor, as well as vaccines targeting genes commonly found in certain types of cancer, including pancreatic cancer. (These developments come as the Trump administration canceled half a billion dollars in funding for research into an mRNA vaccine against infectious diseases.)
If Grippin’s latest trial confirms early research findings, it could represent the next frontier for mRNA vaccine and cancer research.
Immunotherapy drugs work by strengthen the immune system’s ability to fight cancer, often by boosting the power of immune cells called T cells, which attack invaders, or by making it easier for T cells to detect tumors.
The mouse part of the new research found that Covid mRNA vaccination appeared to make the immune system better at recognizing tumors as a threat by stimulating dendritic cells, a type of white blood cell. When dendritic cells detect a threat, they turn on a kind of beacon that leads T cells toward the perceived invader so they can attack it. However, not everyone naturally has T cells that can fight tumors. That’s why scientists think immunotherapies only work in certain cancer patients who take them. In these people, the immune system recognizes cancer cells as a threat, but their specific T cells are unable to stop the tumors from growing.
“It’s just a coincidence whether you have these cells or not,” said Jeff Coller, professor of RNA biology and therapeutics at Johns Hopkins Medicine, who was not involved in the research.
Receiving an mRNA Covid vaccine doesn’t change whether a person has the specific T cells needed to fight their tumors, but it does appear to make it more likely that dendritic cells will detect a tumor as a problem and direct a person’s T cells to the tumor. If these cells turn out to be programmed to be able to kill tumor cells, having an mRNA vaccine that illuminates the target before a person starts immunotherapy can give their immune system a boost that helps cancer treatment work better.
Coller said one reason mRNA technology might be the best tool for eliciting this response is that every cell in the body already contains mRNA.
“We’re really tapping into this natural process that your body already knows how to respond to,” he said. “You’re using your body’s natural system to fight tumors.”
Dougan said it was possible that other factors could have accounted for better survival in people vaccinated before immunotherapy treatment. For example, a Covid infection may have weakened an unvaccinated person’s body and hampered its ability to fight cancer cells. In the past, early studies like this have shown promising results that have not materialized in subsequent trials.
“We have already been misled by retrospective studies,” she said.
Grippin agreed that the findings merited further examination.
“These data are exciting, but all of these findings need to be validated in phase 3 clinical trials to determine whether these vaccines should be used in our patients,” he said.
