As if there arent enough mysteries surrounding the coronavirus, the latest headlines have been about something called COVID-19 rebound. Some people experiencing this phenomenon are seeing a rebound in COVID-19 symptoms after taking Paxlovid , the five-day oral antiviral medication that stops the coronavirus from replicating in the body. Rebound symptoms are typically mild or on par with the original symptoms, and mostly include a sore throat, runny nose, headache and fatigue.

Though scientists dont yet understand why some people experience a resurgence in symptoms, they suspect that the lingering virus is able to start replicating again after people stop taking Paxlovid. So far, none of the rebound symptoms have led to severe disease requiring hospitalization.

Infectious disease doctors say its worth knowing that rebounds can happen as they could prolong ones isolation but really arent a reason not to prescribe the drug, as it continues to do a great job of keeping people out of the hospital.

If I were to be prescribed Paxlovid, I would take it immediately, knowing that even if I were to have some rebound symptoms after completing the therapy, I know that at this point nobody has been admitted to the hospital because of rebound symptoms, Anthony Baffoe-Bonnie , associate professor of infectious disease at the Virginia Tech Carilion School of Medicine and medical director of Carilion Clinic Infection Prevention and Control, told HuffPost.

What causes a rebound in symptoms?

Paxlovid is a five-day course of oral antiviral medications that blocks SARS-CoV-2 from replicating in the body and consequently helps prevent severe disease.

In a clinical trial , the drug was shown to be 89% effective at preventing hospitalization and death. The trial also found that about 1%-2% of people taking the drug experience a rebound in symptoms about two to eight days after finishing the full course though a recent surge in news coverage about COVID-19 rebound has caused an increase in concern. Not everyone who takes Paxlovid will go on to experience a resurgence in symptoms. Lots of people have taken Paxlovid and havent experienced rebound symptoms, Baffoe-Bonnie said.

Its unknown what causes some people to relapse, but the working theory is that at first, Paxlovid stops the machinery in the body that allows the virus to replicate, which leads to an improvement in symptoms. But, in some people, there may be some viral particles that continue to hang out in the body after the five-day antiviral course, explained Khalilah Gates , associate professor of medicine in pulmonary and critical care at Northwestern Universitys Feinberg School of Medicine.

When you stop the Paxlovid, and that machinery starts working again, it starts to replicate that lingering virus, and so you get symptoms again, Gates said. If you had COVID-19 and recovered after taking Paxlovid, but then started to feel sick again a couple days after you finished the medication, Gates said youre probably experiencing the rebound.

What to expect with rebound symptoms

So far, the rebound symptoms are similar to and often milder than the original symptoms. They also tend to resolve in about three to five days. A pre-print case study evaluated the resurgence of symptoms in eight non-immunocompromised people who had taken Paxlovid and found the relapse symptoms were mostly cold symptoms (like a sore throat) along with headache and fatigue.

There is no clear trend as to who might be more prone to experiencing a rebound. According to Gates, we dont have enough case reports to identify who is at risk for a rebound, and at this point, the epidemiology of the rebounds appears to be completely random. You can see it in individuals who are vaccinated, individuals who are not, individuals who are young, individuals who are old, Baffoe-Bonnie said.

The only trend that seems to be persistent, he added, is that none of the individuals who have had rebound to date have gotten sick and gone into the hospital to be hospitalized.

Yes, eligible people should still take Paxlovid

Baffoe-Bonnie said that even with rebounds, Paxlovid is still an excellent drug. Its highly effective at preventing people from getting severely sick and ending up in intensive care. Those benefits are still seen with Paxlovid, whether you have rebound symptoms or not, he said.