mRNA Covid shots may boost the effects of certain cancer treatments, study suggests

STAT News – Sunday, October 19, 2025
By Angus Chen

mRNA-based Covid vaccines from Pfizer-BioNTech or Moderna may have an unexpected benefit for cancer patients who undergo immunotherapy.

A new study suggests that these vaccines might boost the effects of immunotherapy drugs, perhaps by alerting the immune system and helping direct immune cells to attack tumors. That’s in addition to helping protect against Covid, which can be particularly important for cancer patients who can sometimes have weakened immune systems.

The study found that advanced cancer patients who received a Covid vaccine within 100 days before taking an immunotherapy drug during the pandemic lived longer than patients who did not, in a retrospective analysis. Researchers from MD Anderson Cancer Center presented the study at the European Society for Medical Oncology conference in Berlin on Sunday.

The results are intriguing cancer immunologists and oncologists, who reacted with both excitement and caution.

“When I first heard about it, I said, ‘wow, seems unlikely,’” said Ryan Sullivan, an immunologist and cancer researcher at Mass General Cancer Center who did not work on the study. He said he first heard about the work last year, when the group presented earlier data at conferences. “But as I see the data, I think it’s more and more compelling. Obviously, it’s retrospective data, and needs to be validated.”

In particular, experts said, a prospective randomized clinical trial needs to be done to provide stronger evidence that mRNA vaccines for Covid or something similar can actually improve immunotherapy outcomes. The study authors are planning that type of trial, where some patients would be randomly assigned to receive an mRNA vaccine before taking immunotherapy drugs and others would not.

The current study compares patients who happened to have received an mRNA Covid vaccine before beginning immunotherapy to those who did not from 2015 to 2022. The study also reviews experiments done in mice and lab cell cultures, which investigated why receiving an mRNA shot may help boost cancer immunotherapies. Still, all of those experiments can be prone to key biases and limitations that make drawing definitive conclusions difficult.

The idea for the study came from experiments Adam Grippen, a cancer researcher and radiation oncology resident at MD Anderson and lead author on the study, performed as a graduate student at the University of Florida in 2016.

He’d been studying neoantigen cancer vaccines, many of which also use mRNA and are focused on helping the immune system recognize cancer mutations and are personalized to each patient’s tumor. These personalized vaccines have shown promising results in early phase clinical trials in recent years in improving outcomes for patients with melanoma when combined with the immunotherapy drug Keytruda.

At the time, Grippen wanted to test if a personalized mRNA vaccine would drive a stronger anti-cancer immune response than a generic mRNA vaccine without any particular cancer target in mice. That turned out to be the case, Grippen said, “but we were excited to find that the mRNA vaccine that wasn’t personalized also had anti-tumor effects.”

That made him start wondering if any mRNA vaccine, perhaps some kind of universal, off-the-shelf product, could have a role in treating cancer.

Then the Covid-19 pandemic struck, and hundreds of millions of patients received an mRNA vaccine for the coronavirus. Grippen wondered if that vaccine might have stimulated an immune response against cancer, similar to what he’d seen in his mice in graduate school.

In an analysis including several hundred patients, Grippen compared melanoma or lung cancer patients who received the Covid vaccine within 100 days before starting a checkpoint inhibitor, to patients who had not gotten the vaccine before starting the drugs. Checkpoint inhibitors, such as Keytruda and Yervoy, work by blocking natural brakes that inhibit immune T cell activity and are often co-opted by tumors to “hide” from the immune system. Taking that away helps T cells kill cancer.

“When we saw these results, that patients who received mRNA vaccination had nearly double overall survival compared to those who had not, it got us excited about the potential to boost responses in patients,” Grippen said. “We are using a Covid mRNA vaccine that is widely available. If we can demonstrate in a phase 3 clinical trial that they improve responses to immune checkpoint inhibitors, it can rapidly impact patient responses nationwide.”

For lung cancer patients, getting a Covid vaccine before initiating immunotherapy increased the median overall survival from 20.6 months to 37.3 months in the study.

Such results could also lead to developing a kind of “universal” mRNA vaccine designed specifically to boost responses to immunotherapy, if they continue to hold in prospective randomized trials, a gold standard in clinical experimentation. Like Grippen, other experts told STAT that the potential for a commercially available product to immediately improve immunotherapy outcomes at this level is tantalizing, but cautioned against jumping to conclusions.

For one, the cohort of lung cancer patients that didn’t get Covid vaccination before immunotherapy included cases from 2015 to 2022. Over that time, the standard of care using immunotherapy has improved, making it hard to know if the improvement in survival observed in the study is due to the vaccine or simply advances in cancer care. Grippen told STAT that most of the patients were treated after 2017. He still saw an association between vaccination and survival when controlling for treatment regimen and year, though he also agreed that the findings need to be validated in a randomized trial.

The potential biological reasons why a Covid vaccine would boost immunotherapy efficacy are intriguing. The Covid mRNA vaccine causes the body to release type 1 interferon, a kind of immune signaling protein associated with an anti-viral response and can be a kind of immunological alarm system. This inflammatory protein is the main culprit for the strong side effects associated with the mRNA Covid vaccines.

Grippen’s mouse experiments suggested that interferon, along with other inflammatory immune signals, may be leading immune cells called macrophages and dendritic cells to coordinate a stronger immunological response against cancer and drive T cells to attack the tumor. Once activated, immune checkpoint inhibitors can help those T cells further fight the cancer.

Biologists have long known about interferon’s ability to trigger this kind of immune reaction, and biotech and pharma companies have tried to drug the interferon pathway to try to treat cancer. However, these attempts have so far failed in clinical trials in the past.

“Just because those failed, does not mean this is not right,” said Brian Brown, an immunologist at the Icahn School of Medicine at Mount Sinai who did not work on the study. One possible explanation might be that the mRNA vaccine might be able to hit upon a narrow Goldilocks dose of interferon to get a therapeutic effect, though that remains to be investigated.

If nothing else, “the data are very provocative. I think the idea they touch on is very exciting, but more research needs to be done,” Brown said. “More than anything, it shows us the power of this technology, and how much needs to be learned. At the same time funding is being cut for mRNA vaccine research.”

In August, the Trump administration cut roughly half a billion dollars in research funds for mRNA vaccines for infectious diseases, raising concerns that related cancer research might also be defunded. But if these results are true, Brown said, then it means there is a huge imperative to continue studying mRNA vaccine technology across disease areas. A potential to significantly improve the survival of cancer patients, he said, depends on it.

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