Rebound COVID Is Just the Start of Paxlovid’s Mysteries

The first data on Paxlovid, out last November, hinted that the COVID antiviral would cut the risk of hospitalization and death by 89 percent. Pundits called the drug “a monster breakthrough,” “miraculous,” and “the biggest advance in the pandemic since the vaccines.” “Today’s news is a real game-changer,” said Albert Bourla, the CEO of Pfizer, which makes the drug. The pills are “a game changer,” President Joe Biden repeated a few months later.

Now, finally, the game is being changed. The government has ordered 20 million courses of Paxlovid, committing half of the $10 billion in additional COVID funding that is being negotiated in the Senate; and Pfizer says that the number of patients taking the drug increased by a factor of 10 between mid-February and late April.

But as the treatment spreads, so too does confusion over its effectiveness and side effects. Patients have complained of a bitter, metallic taste, or one like , the whole time they were on the drug. More concerning, some have reported experiencing a second round of symptoms, and going back to testing positive, when the pills were done, a phenomenon that’s become known as “.” Meanwhile, Pfizer has never published any final data on the use of the drug by vaccinated patients, leaving medical professionals with about how the drug works for people who have received their shots—which is to say, most of the adult population in the U.S. “We’re all riding on hope at this point,” Reshma Ramachandran, a family-medicine doctor at Yale, told me.