Throughout the pandemic, one of the biggest unknowns about the coronavirus has been how long people are immune after they catch it and recover. Early indications were that it must provide some immunity, since if multiple infections were possible, they would probably be common. But even a year-plus into the health crisis, the exact length of that protection isn’t clear.
A recent study from the UK provides some more data, suggesting that after a person recovers from COVID-19, their chance of getting the virus is reduced by at least 83% for at least five months. The study followed 20,000 healthcare workers, including 6,614 participants who had tested positive for antibodies. Compared to those who hadn’t contracted COVID, those who had were 83% less likely to be infected again. The actual protection may be higher than that, since the investigators found 44 “possible” reinfections in that group.
The study hasn’t been peer-reviewed, but you can read several experts’ reactions here at the UK’s Science Media Centre, and detailed news stories like this one from Nature that provide context.
The study’s results more or less agree with previous work, including this study that found healthcare workers with spike protein antibodies had better than 90% protection for 6 months.
CDC guidelines state that people who have had COVID within the last three months don’t need to quarantine if they are exposed again. That sure makes it sound like people are immune for three months, but they go on to clarify:
Evidence does not indicate the definitive absence of re-infection during this period, only that risks of potential SARS-CoV-2 transmission from recovered persons are likely outweighed by the personal and societal benefits of avoiding unnecessary quarantine.
In other words, it may be possible to become infected again within three months, but it doesn’t seem to be likely.
What does this mean if I’ve had COVID?
We’ve been living through a time of so much uncertainty, with so many unanswered questions, and unfortunately this is still yet another gray area. Over the next year or two we’ll probably get a better sense of how long protection lasts. (That applies to the vaccine, too: we know it works for at least two months, but it hasn’t been around long enough for us to know whether immunity fades after months, or years, or lasts for a lifetime.)
So, here’s what experts are recommending: First, you may find it comforting to know you probably have some protection. That’s good news. But it’s not actionable news: You still have to do basically the same stuff as the rest of us.
It’s still important to wear masks, for example, and to abide by all the usual social distancing rules. Don’t think you can stand close and cough on people freely or anything like that.
You should also still get the vaccine when it becomes available for you. The CDC says that you shouldn’t get the vaccine while you have COVID, but that getting vaccinated after you have recovered is fine. If you got antibody treatment while you were sick, that could be a reason to delay vaccination, but the infection itself is not.