We can propel humans into space and perform complex organ transplants, but somehow we still don’t have a vaccine for the common cold. While certainly not the deadliest virus facing humankind, colds are downright annoying, can drain your sick days away, and wear at your sanity as you wheeze through your one temporarily clear nostril.
So, if we can create a vaccine for a novel virus in under a year, what’s stopping scientists from inoculating us against the sniffles? A lot, it turns out.
Why don’t we have a vaccine for the common cold?
The majority of colds are caused by a group of viruses called the human rhinoviruses, of which there are 169 known genotypes, according to Alex Greninger, associate professor of lab medicine at the University of Washington Medical Center. Other viruses, like metapneumovirus, the common human coronaviruses (distinct from SARS-CoV-2, the virus that causes Covid-19), and parainfluenza virus, can all cause the common cold, too, Greninger says.
We define the common cold as a group of symptoms that affect the upper respiratory tract, including nasal congestion, sore throat, coughing, and a runny nose. But, diagnostically, we don’t differentiate what causes colds. This is mainly because there are no vaccines or antiviral drugs against mild respiratory viruses anyway. Since that’s the case, doctors aren’t reimbursed for running diagnostic tests on cold pathology; the technology exists, but insurance companies won’t pay for it, according to Greninger.
Even just focusing on rhinovirus genotypes, making a single, effective, one-time vaccine would be difficult. “We can make really good vaccines against these guys,” Greninger tells Inverse. “We just can't do it to all of them.”
Rhinoviruses evolve very quickly, Greninger says, probably too quickly for vaccine formulators to keep up with. These evolutions come from myriad mutations as the rhinovirus reproduces.
“The virus is intentionally sloppy in reproducing itself,” says Lawrence Stanberry, a professor of pediatrics focusing on global health at Columbia University. In other words, as the virus reproduces, creating more little rhinoviruses in a host, they’re not all going to be genetically identical, which works to the virus’s advantage. He estimates that every iteration has some kind of genetic mutation, but that doesn’t necessarily create a new strain of rhinovirus. But, compounded over the years, those changes add up.
“The virus you got a couple of years ago has changed just enough to have you get sick again,” he says.
Has anyone tried to make a vaccine for the common cold?
In 1975, researchers conducted a human clinical trial of two rhinovirus vaccines to determine whether a vaccine would be safe and if it could actually induce an immune response. While just one vaccine was able to provoke an antigenic response to only 30 percent of the viruses included in the formula, the authors still concluded that a vaccine protecting against multiple strains of rhinovirus “should be tested to develop practical control measures for rhinoviruses.”
That concept would come to fruition decades later. A paper published in Nature in 2016 details a rhinovirus vaccine trial in rhesus macaque monkeys. One formulation targeted 25 rhinovirus genotypes, while another targeted 50.
The authors concluded that a vaccine that targets multiple variants of the rhinovirus could create a robust immune response against dozens of virus genotypes. That sounds promising. However, even this 50-valent formula would only protect against about one-third of the human rhinovirus genotypes that are currently circulating through humans. At best, it would lower someone’s chances of getting infected by 30 or 40 percent.
That’s not nothing, but there are a few things to consider about the advantages of lower risk rather than near-zero risk. For one, Greninger says we’ll likely “see a shift in what’s being transmitted in the community.” Since there are so many rhinoviruses, people will simply carry and fall ill from strains that the vaccine doesn’t cover. He points to the rotavirus as an example, which has two oral vaccines. “You see dramatically less, so that's the most important thing, but you do see continued circulation of rotaviruses that aren't included in the vaccine.”
He also imagines potential backlash when the public realizes that a cold vaccine would only mitigate the sickness, not eliminate it. “People will come out and be like, ‘Oh, you didn't get them all, so you lied to me,’” he says.
Will there ever be a vaccine for the common cold?
This is difficult to forecast, but it looks like, for the immediate future, we’ll have to deal with colds on our own. A number of other viruses take priority, like influenza, which was the top virus that killed people before SARS-CoV-2.
It’s also expensive to develop, test, administer, and update vaccines, especially for something as widespread as the common cold. The economic impact, Stanberry says, mostly affects workdays and school days, and it’s not clear how much could be recovered if we had a vaccine handy. “It's a little bit of a challenge to look at the economic side and get a sense of what our society is willing to pay in order to not have a cold?” he says. While a vaccine could recoup some economic loss, it’s also not saving lives. It’s arguably more pressing to focus on creating vaccines against viruses that are likely to kill people.
He does suggest it could be useful to vaccinate immunocompromised patients against even some rhinovirus genotypes. For those with conditions like chronic obstructive pulmonary disease (COPD), a cold can exacerbate typical COPD symptoms and potentially lead to serious bacterial infections like pneumonia. Others with respiratory conditions, like asthma and cystic fibrosis, could also benefit.
As for healthy folks, we'll continue to sneeze, wheeze, and cough through the tribulation that is the common cold.
