Partly. "We all have what we call innate immune systems, which protect us against viruses we’ve never seen before," says Professor Johnston. "We also have acquired immunity, where our bodies 'learn' from infections we’ve seen previously and have immunity to them, such as mumps or chickenpox."
The number of colds we get depends on how strong both these immune systems are. "People vary depending on their genetic make-up and there are at least 40 genes found to control our immune defences," adds Professor Openshaw. "So you may simply be lucky or unlucky in terms of the pattern you’ve inherited."