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Even after vaccinating everyone on Earth against the coronavirus, COVID-19 could continue to spread.

That's because scientists aren't yet sure whether the vaccines currently being deployed actually stop disease transmission or if they merely prevent symptomatic disease, Trinity College Dublin immunologist and biochemist Kingston Mills told New Scientist. That means there's a chance the vaccine doesn't actually keep people from catching and spreading COVID-19, but simply makes them less likely to suffer from it.

Scientists are still trying to figure out whether the vaccines actually prevent the virus from spreading, but Scientific American notes that it wouldn't be unheard of if they didn't — the hepatitis B vaccine doesn't prevent transmission, for instance. If that ends up being the case, experts told SciAm, COVID-19 will remain a public health concern — no matter how many people get vaccinated — even after the pandemic finally ends.

"I don’t see that these vaccines will be eliminating SARS-CoV-2 any time in the coming years," Mills told New Scientist.

That said, mass vaccination will play a major part in ending the pandemic's devastation, even if the coronavirus technically continues to spread and infect new people under the radar. Being able to prevent serious or even mildly symptomatic cases of COVID-19 will be a game changer in getting life back to normal, ending lockdown, and making it safe to once again be around other people.

The issue is that even when that happens, new cases of the coronavirus will likely pop up among those who didn't or couldn't get vaccinated if those who were inoculated can in fact still spread the disease. Plus, New Scientist notes, the coronavirus could theoretically mutate as it spreads among people or different animal species, potentially causing new outbreaks.

"I think this virus is here to stay," Public Health England epidemiologist Susan Hopkins told New Scientist.