Right now, in the midst of a global pandemic, it might be hard to think more than a few months in advance. But centuries of data tell us that this too will end—it just won’t mean the virus is gone forever. Years of data tell us that it’s incredibly difficult to eradicate an infectious disease even with a highly effective vaccine. A study out this week in the journal Science, suggests that over the next few years, the novel coronavirus could morph into a seasonal disease, similar to the common cold or, at worst, the yearly influenza bug.
To better understand how the new virus might behave in years to come, the researchers looked at how other known coronaviruses function. SARS-CoV-2, the official name for the virus that causes COVID-19, is not the first coronavirus humans have encountered. Scientists are currently aware of six coronaviruses that make humans sick. Four of them cause the common cold, which is almost exclusively a benign upper respiratory disease, and the other two—SARS and MERS—are far more deadly.
While the two deadly ones are largely contained or eliminated, and never really spread across the globe with the same speed and magnitude as SARS-CoV-2, the other four strains have become endemic in most places around the globe—they regularly make their way through populations, spreading easily enough that they simply cannot be contained.
For the study, the researchers used the four endemic coronaviruses’ characteristics to model what SARS-CoV-2 could look like years down the road. One main characteristic they looked at was how severe the disease was in kids. Young kids, under the age of five, typically have strong immune systems, and also usually have their first encounter with a common cold. Over time, the more they are exposed to the viruses, the better their immune response is and the less severe cases they get. By the time they are older adults, they’ve encountered the virus so many times that their immune systems can handle it. In the case of this pandemic, though, the virus was new for everyone, and because the immune system weakens with age, older adults are far more vulnerable to COVID-19.
The study predicts that once most people have been exposed to the virus—hopefully more through vaccination than direct infection—the novel coronavirus could eventually become an endemic virus, similar to the those that cause the common cold, and will mainly affect kids under five in the form of a relatively benign bug.
It is, of course, impossible to predict what will happen in the future, but some current data backs up this model. As wonderful as the new mRNA vaccines are, none of them are 100 percent effective at preventing COVID-19. As Popular Science reported last month, it might still be possible for someone to be vaccinated and immune from COVID-19 yet still carry the virus and spread it around. “It would not be so far-fetched to have a vaccine that protects you from developing the worst COVID disease, but you could be infected and you could be spreading it [without] getting really sick,” Jeffrey Bethony, a professor of microbiology, immunology, and tropical medicine at the George Washington University School of Medicine and Health Sciences, told PopSci.
In late-stage clinical trials, both Moderna’s and Pfizer’s vaccines were 100 percent effective in preventing severe forms of COVID-19, demonstrating that exposure to the coronavirus results in a less severe bout of the disease should you encounter the virus again later. Further support comes from reinfection rates. While researchers are still investigating how common it is to get COVID-19 twice, it appears to be relatively rare, and when it does occur, second cases are generally more mild than the first.
Understanding long-term COVID-19 immunity, both from infection and from the vaccine, will take a couple of years, at the least. While there’s good data right now to suggest that immunity lasts upwards of eight months, no one knows for sure. And how dangerous the virus will be in a few years depends largely on our overall immune response to it. One thing is for sure, though: our best way out of the pandemic is widespread protection, and vaccination is the best way to save the most lives while also generating that immunity.