The short answer is twofold. First, what we think of as a cold is actually caused by many different viruses. Even the most common among those, rhinovirus, has over a hundred different strains
Curing" a cold would actually mean eradicating a long list of respiratory viruses that happen to cause similar symptoms. Those symptoms, incidentally, are mostly just your immune system kicking into high gear to fight off an infection, something that can manifest as inflammation in the throat and congestion in the nose.
while sniffling and coughing is no fun, a cold is pretty low down on the list of ailments that need curing. It can be a concern for infants, the elderly, or those with pre-existing respiratory conditions, but "for the majority of us, a common cold is more annoyance than threat
Every year, there are multiple strains of the flu circulating. If we can vaccinate against the most common strains of the flu, it seems like we should be able to do the same thing for colds. But it doesn’t quite work that way.
There are only about three strains of flu each season, while “there are usually 20-30 different types of rhinovirus circulating each season in one geographic area,” explains Yury A. Bochkov , an associate scientist in the department of pediatrics at the University of Wisconsin School of Medicine and Public Health. Only about 10% of those will show up again the next year. That means, Bochkov says, that public health officials “cannot predict the spectrum of rhinovirus types for an upcoming cold season.”