it affects manly men, research suggests Man flu: It's real. Sorry, ladies. "Manlier" men are less resistant to the effects of one strain of the flu, new research suggests. Those in favour of the existence of the dreaded "man flu" had been supported by previous findings that women have a stronger immune response than men, but the reasons remained unknown until now. Scientists from the US and France identified a cluster of genes that had already been linked to poor immune response in males. These genes are responsible for lipid biosynthesis, where a complex chemical compound is made from simpler components. The expression of these genes appeared to be increased by testosterone. By analysing blood serum in 53 females and 34 males, the researchers discovered men with higher levels of testosterone displayed weak antibody responses to the flu vaccine when working with the H3N2 strain - a serious and prevalent strain globally. Those men with low levels of testosterone and females didn't show a decrease in their antibody response to the vaccine. Dr Alan Hampson, Chair of the Australian Influenza Specialist Group, who was not involved in the study, said it was important to recognise the difference between males and females occurred most strongly with the H3N2 strain, but to a lesser extent and not at all with the two other strains studied [B and H1N1], respectively. "The results when you look at morbidity and mortality of influenza globally are rather mixed," said Dr Hampson. In some places we see there are more severe infections in males but in others we see more severe infections in females and it does differ with age. Dr Hampson said the findings were another piece in a very large jigsaw, but should not be encouraging either sex to skip vaccinations, or for females to be offered a diluted dose. "We know that in some parts of society women are the care-givers who really do become exposed to influenza so it's good if they do produce a better immune response to the vaccine," said Dr Hampson. As to males receiving more sympathy while suffering the flu however, or even the existence of the "man-flu," Dr Hampson remains unconvinced. I think anybody who gets the flu and gets typical clinical symptoms deserves sympathy.