The surprising reason why man flu is a real thing Their symptoms look similar, but the guy is feeling it way worse. Science says. Men with higher levels of testosterone have weaker immune systems than both women and the 45kg weaklings they stuffed into their high-school lockers, a new Stanford study has found. "There are marked differences between the sexes in their immune response to infections and vaccination, with females often having significantly higher responses," reads the study, which was posted on Proceedings of the National Academy of Sciences. Men with high testosterone levels showed the lowest antibody response to flu vaccinations. Men are suffering! Stanford immunology professor at Mark Davis told NBC News. They aren't as resistant. Women are superior. There's no way around it. The research team drew blood from 37 men and 54 women and studied how flu vaccines affected the subjects' immune system proteins and cells. As expected, the men had on average a smaller response to the vaccines.