Why there’s still no cure for the common cold

You may be fighting off a cold at the moment, or just getting over one.

As the high-season for certain common cold viruses begins to wind down this month, to be followed by the flu season soon after, we’re starting to hear about going in for our annual flu vaccine. So why does influenza have a vaccine — albeit with limited and varying effectiveness — but not the other viruses that give us the cold? It’s complicated. The common cold is actually an infection of the upper respiratory tract, caused by any one of many viruses, each with multiple variations. For example, one common culprit is the rhinovirus, which has approximately 100 variations. Finding a good target for a vaccine with such a huge number of potential suspects would be a challenge.

We’ve seen how hard it is to predict the two or three dominant strains of influenza that circulate in any given year for a flu vaccine.

Even so, attempts are still being made to develop vaccines against some of the viruses that cause the common cold.

Some might think attempting to develop a cure for the common cold is a trivial pursuit. For many of us it’s just a minor annoyance that gives us a drippy nose, a cough, a sore throat and some time in bed resting. But if you add up all the time it takes away in lost productivity, along with the more serious symptoms these viruses can cause among vulnerable populations, a vaccine for cold viruses would make a huge impact.

Researchers have estimated that the common cold costs close to $25 billion (U.S.) annually in lost productivity in the U.S. Colds spread through workplaces, schools and public transit, multiplying the impact. Plus, there are the extra costs of over-the-counter cold and flu medication and prescription antibiotics — not to mention the cost to our health system — all to manage symptoms of the common cold. In the Ontario Burden of Infectious Disease Study, published by the Institute for Clinical Evaluative Sciences and Public Health Ontario, the common cold was found to cause over 3 million health-care visits a year.

Colds can also lead to more severe illnesses. We used to think viruses like rhinovirus and coronaviruses only caused mild illness, but that thinking has changed. Children under 5 years of age, people over 65 and pregnant women are most at risk from viral respiratory infections, especially influenza. So too is anyone with a chronic respiratory disease such as asthma, underlying heart disease, diabetes, obesity, a neurological disorder or a weakened immune system. For these more vulnerable groups of people, a common cold or flu can be much more serious.

Despite the difficulties, progress is being made. Researchers are working on a vaccine to protect infants against respiratory syncytial virus (RSV), the most common cause of respiratory infection in infants under 1. In adults this would usually cause — you guessed it — a common cold. But for babies, RSV can have more serious consequences, including infections of the lower airways, such as bronchiolitis (inflammation of the lower airways) or pneumonia.

In the meantime, until we come up with more tools to fight the cold, keep washing your hands, stay home from work when you’re sick, toss used tissues and sneeze into your elbows, not your hands. And as cold season turns to flu season, at least there’s a vaccine for that. Dr. Jonathan Gubbay is an assistant professor of pediatrics and laboratory medicine and pathobiology at the University of Toronto. He is a medical microbiologist at Public Health Ontario. Doctors’ Notes is a weekly column by members of the U of T Faculty of Medicine. Email doctorsnotes@thestar.ca.