The Washington Post

Biden’s rebound is no reason to avoid Paxlovid


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.

Paxlovid is an oral treatment that works by stopping virus replicatio­n. When given to vulnerable individual­s early in the course of illness, it reduces hospitaliz­ation or death by nearly 90 percent.

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 A much larger study supported by funding from the National Institutes of Health, online but not yet peer-reviewed, found a recurrence rate of 2 to 6 percent — a similar rate to patients who took another antiviral pill, Merck’s molnupirav­ir.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 highprofil­e 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-fitsall 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.

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