When I saw this headline from NBC News this morning I momentarily wondered if we’d stumbled into a British version of Groundhog Day. British Prime Minister Boris Johnson is in self-isolation after being exposed to the novel coronavirus. He apparently took part in a meeting with Member of Parliament Lee Anderson on Thursday. Anderson later developed symptoms of COVID and tested positive so BoJo was advised to keep to himself for a while.

U.K. Prime Minister Boris Johnson, who battled a coronavirus infection in an intensive care unit earlier this year, is in self-isolation after being exposed to the virus again, officials said Sunday.

In a statement, No. 10 Downing Street said Johnson wasn’t experiencing symptoms but would follow guidance from Britain’s National Health Service, which recommends self-isolation after prolonged exposure to someone who has the virus.

“He will carry on working from Downing Street, including on leading the government’s response to the coronavirus pandemic,” the statement said.

Is this being done out of an abundance of caution? I can see how the British Prime Minister’s office would want to set a good example and lead by following their own directives, I suppose. But Johnson famously contracted COVID-19 back in March. He was among the first foreign leaders to come down with the disease. Doesn’t that mean he’s supposed to have antibodies now and can neither catch nor transmit the virus anymore?

One thing that the medical community has been learning about COVID thus far is that the immunity you achieve after being infected can be short term and weaker in some cases than previously anticipated. One factor seems to be the severity of the symptoms you suffered. People who only take on a very light load of the virus and show few if any demonstrable symptoms may wind up with a very low level of immunity. Those who have to fight off a heavier load over a protracted period of time may have significantly stronger levels of antibodies and, subsequently, immunity.

Johnson wasn’t one of those asymptomatic people who quickly shrugged it off in a day or two as Donald Trump did. BoJo famously told the press that he was in the ICU and only survived thanks to “liters and liters of oxygen.” He went so far as to claim that his doctors were preparing to announce his death. In short, the Prime Minister was hit hard and he had to fight it for a long time.

If that’s the case and our current understanding of how the virus works is anywhere near accurate, Johnson should be brimming with antibodies and be close to immortal in terms of COVID-related mortality. Of course, as I already said, he may remain fit as a fiddle and never even test positive. He’s continuing to do his job in isolation so perhaps that’s the case and this really is all just window dressing to set a good example.

As we’ve discussed here previously, there have already been a couple of confirmed instances of people who were sickened by the virus becoming reinfected later on. But it sounds as if the CDC still doesn’t have a handle on that question and they don’t know how commonly it happens. Some of the first reports of double infections were later written off as people who had delivered a false positive on an earlier test before actually contracting the sickness later in the year.

Johnson has repeatedly stated that his battle with COVID left him feeling depleted and weaker than he’d been before. If he really does come down with it a second time we would have to wonder if he could really beat it again. But if nothing else, it would definitely prove that immunity to the novel coronavirus can be fleeting in even the worst of cases, so we’re probably going to be vaccinating people a lot more often than we do for the common flu.