Q. Can I catch the same cold twice?
A. Yes, you can catch the same cold twice, depending on the strength of your immune response.
Most of what we know about immunity to cold viruses is based on studies performed in the late 1950s and early ’60s. These were experiments in which volunteers — the term “volunteer” may be a bit generous here as the subjects were typically medical students or military recruits whose participation may have been less than fully voluntary — were intentionally infected with cold viruses.
In one landmark study from the late ’50s, over 1,000 stalwarts were inoculated with the infectious nasal secretions from a patient with an active cold.After becoming infected and being allowed to recover, the subjects were challenged again with the same virus to study their response. In a later, particularly rigorous study from 1963, 50 subjects were confined to a dormitory for an entire month to assess their ability to withstand reinfection with the same cold virus.
The results of these studies showed that for many people, infection with a cold virus can indeed provide effective immunity against subsequent exposure to that particular virus. More than half of the study participants made sufficient amounts of antibodies and were protected. Those who had a less robust antibody response, however, were not protected and came down with a cold after being reinfected.
But there are hundreds of viruses and viral subtypes that can cause a cold, and immunity to one type does not extend to others. Rhinovirus, for example, the most common cause of colds, has over 100 subtypes, each of which varies slightly in its genetic makeup and each of which can cause a cold. In addition, the cause of 20 percent to 30 percent of colds still remains unidentified, despite advances in molecular diagnostics.
So, while infection with a cold virus can protect against reinfection with that same virus, the existence of hundreds of different types of cold viruses means that we will always be susceptible to catching colds.