President Biden has tested positive for the coronavirus again, which is being attributed to his use of the antiviral pill Paxlovid. While a second round of isolation is inconvenient, the possibility of such a rebound should not deter Americans from making use of this highly effective treatment.
This, in combination with vaccines, is a game-changer for how we understand risk from covid. Early in pandemic, the coronavirus was greatly feared because it caused potentially fatal respiratory distress, even among healthy young people. Those who have been vaccinated and boosted are already at much lower risk from serious illness. The addition of Paxlovid turns the disease into a manageable ailment, allowing most people to go about their normal lives.
Biden’s covid experience is testament to the power of vaccines and treatments. He had no more than mild symptoms and kept working. By Day 6, after he completed the five-day course of Paxlovid, he tested negative.
His physician has monitored for the possibility of rebound, which manifests as someone becoming symptomatic or testing positive again within several days of testing negative. Pfizer, the manufacturer of Paxlovid, initially reported that rebound occurred in about 2 percent of cases. This was only slightly higher than in people who did not take Paxlovid, who had a 1.5 percent recurrence rate.
These earlier studies were done before the omicron subvariants became dominant. Anecdotal reports suggest that the rebound rate might be substantially higher with the current strains, though the research is mixed. A small study from the Mayo Clinic found that only 4 out of nearly 500 patients who took Paxlovid subsequently had rebound. A much larger study supported by funding from the National Institutes of Health, online but not yet peer-reviewed, found a recurrence rate of 2 to 6 percent — a similar rate to patients who took another antiviral pill, Merck’s molnupiravir.
In other words, Biden is in the minority of patients who tested positive again. His recurrence occurred on Day 9, which is the norm according to a report published by the Centers for Disease Control and Prevention. Biden has no new symptoms yet, and even if he develops them, they are likely to be mild. The CDC report found that less than 1 percent of patients experiencing Paxlovid rebound had severe enough symptoms to warrant an emergency department visit or hospitalization.
Why Paxlovid rebound occurs is not fully understood. Studies suggest it is not due to reinfection, to ineffective treatment or to the medication being less capable of targeting emerging variants. More likely is that the five-day treatment is not enough. Perhaps Paxlovid suppresses viral replication initially, but if it’s stopped prematurely, there might still be virus that could cause a recurrence.
Research is ongoing to see whether Paxlovid should be administered over a longer period — for example, for 10 days instead of five. In the meantime, the Food and Drug Administration has not authorized for the drug to be taken if symptoms recur, though some high-profile individuals, most notably Biden’s chief medical advisor Anthony S. Fauci, have taken a second course for their own relapse.
The FDA should reevaluate the duration of Paxlovid administration and which patients would benefit from a repeat course. In addition, the CDC needs to clarify isolation guidelines. At the moment, the CDC says that patients who test positive again should isolate for another five days. This makes sense in principle; if someone has a positive antigen test, they are probably shedding enough virus that they could infect others.
But what if that person is still testing positive by Day 6? The CDC is not asking for repeat testing after five days, even though a residual positive result would still imply contagiousness. It is also not recommending routine testing for people who took Paxlovid. Without daily tests, Biden’s diagnosis wouldn’t have been picked up. How many other cases are being missed? And if relapse is something that can occur in individuals who didn’t take Paxlovid, should everyone be tested even after resolution of their symptoms?
All of this is further evidence of how difficult it is to avoid coronavirus transmission. Rather than seeing Paxlovid rebound as a deterrence to effective treatment, this could be a moment to rethink our inconsistent and highly disruptive isolation policies.
In this next phase of the pandemic, we might need to discontinue one-size-fits-all isolation guidelines. Instead, people who wish to prevent infection and the possibility of long covid should ask others to test before seeing them. Meanwhile, the emphasis for everyone else should be on getting vaccinated and using treatments such as Paxlovid for when — not if — they contract the virus.