A pair of studies published this week challenge long-held assumptions in two separate fields — one showing that a father's exercise habits can be inherited by his offspring, and another suggesting that mRNA COVID-19 vaccines may dramatically improve the effectiveness of cancer immunotherapy. Neither finding is yet ready for clinical or lifestyle recommendations, but both open new research directions with immediate experimental implications.

Father's Running Improves Offspring Cardiorespiratory Fitness

Researchers put male mice through an endurance training regimen, then tested their offspring — who never exercised — for aerobic capacity. The results were clear: pups from trained fathers had higher maximal oxygen uptake (VO2max), lower lactate accumulation during exercise, and faster maximum running speeds compared to pups from sedentary fathers. The effect was not explained by changes in heart size or cardiac output, the traditional markers of cardiovascular conditioning. Instead, the calf muscles of the offspring showed a shift from glycolytic fibers (fast-twitch, anaerobic) to oxidative fibers (slow-twitch, endurance-friendly).

The key molecular driver turned out to be PGC-1α, a master regulator of mitochondrial biogenesis and oxidative metabolism. The team genetically engineered male mice to overexpress PGC-1α in their muscles without any exercise at all. The offspring of these engineered fathers — who did not inherit the PGC-1α gene itself — still showed the same endurance and cardiorespiratory benefits as pups from exercised fathers.

The transgenerational signal travels through small RNA molecules in sperm. When the researchers injected small RNA extracted from the sperm of trained fathers into normal fertilized eggs, the resulting offspring displayed identical endurance improvements. The effect did not persist beyond one generation. In a parallel human observation, sperm from elite endurance athletes showed microRNA changes similar to those seen in the trained mice.

DOI: 10.1016/j.cmet.2025.09.003

mRNA Vaccine Cuts Cancer Immunotherapy Death Risk by 49%

The second study, a retrospective analysis of patient records, examined what happens when patients with advanced non-small cell lung cancer (NSCLC, stage III/IV) or melanoma (stage IV) receive an mRNA COVID-19 vaccine within 100 days of starting immune checkpoint inhibitor (ICI) therapy. The results were unexpected.

For NSCLC patients, the 36-month overall survival rate was 30.8% in the unvaccinated group versus 55.7% in the vaccinated group — a 49% reduction in death risk (HR = 0.51). For melanoma patients, the death risk dropped by 63% (HR = 0.37), with survival rates of 44.1% versus 67.6%. Median survival in NSCLC extended from 20.6 months to 37.3 months.

The most striking finding: even patients with PD-L1 expression below 1% — so-called "immunologically cold" tumors that typically do not respond to checkpoint inhibitors — showed a 47% reduction in death risk (HR = 0.53). This suggests the mRNA vaccine may extend the benefit of immunotherapy to patients who would otherwise be expected to derive little to no effect.

Importantly, influenza and pneumonia vaccines did not produce the same effect, ruling out the simple explanation that "healthier people get vaccinated." The mechanism appears specific to mRNA vaccines, possibly through innate immune activation that primes the tumor microenvironment for checkpoint inhibitor activity.

Caveats are substantial. This is an observational study, not a randomized controlled trial. In the United States, COVID-19 vaccination was more frequent among healthier populations, creating a potential "healthy vaccinee" bias. No adjuvant-immunotherapy combination has yet passed a Phase 3 randomized trial. Phase 3 trials are now being planned, and clinical application will require additional data.

DOI: 10.1038/s41586-025-09655-y

These two studies share a common thread: they identify biological mechanisms that were previously invisible. The exercise inheritance work opens a molecular pathway for transgenerational fitness effects that could reshape how we think about parental health. The vaccine-immunotherapy synergy suggests that existing mRNA vaccines may have an off-target immune benefit that no one designed for — and that no one has yet proven in a randomized trial.

Neither finding changes practice today. But both provide testable hypotheses that labs can begin working on tomorrow.