Treated with the Covid pill “Paxlovid”: Biden was corona positive again after three days: this is due to the “rebound effect”

Corona again? US President Joe Biden has now had to go into isolation for a second time. His test came back positive – although he was negative three days ago. According to his doctor, the so-called “rebound effect” is responsible for this.

US President Joe Biden has again tested positive for the corona virus. He has once again gone into isolation, although he “remains feeling pretty good,” his doctor, Kevin O’Connor, said in a statement from the White House on Saturday in Washington. O’Connor referred to the so-called rebound effect that can occur after treatment with the Covid drug Paxlovid.

Biden had just ended his isolation three days ago after two negative corona tests and returned to the Oval Office. “Guys, today I tested positive for Corona again,” wrote the President on Twitter on Saturday. “I have no symptoms but I will isolate myself to ensure the safety of everyone around me. I’m still at work and will be back soon.”

The 79-year-old US President tested positive for the first time on Thursday a week ago. He isolating himself in his White House apartment and has continued to work, but slightly less than usual. Biden has been treated with the Covid drug Paxlovid. And according to physician O’Connor, this is exactly what is responsible for the fact that his test was positive again. This is what is known as the “rebound effect”.

The Covid-19 rebound is characterized by a recurrence of symptoms or a new positive virus test after a negative test.

The preparation is used to protect those who are at high risk of developing a severe course of the corona virus. The Paxlovid tablets from the US pharmaceutical company Pfizer are also approved in Germany and can be taken at home if prescribed by a doctor. They are designed to inhibit virus multiplication in the body.

Real-world data, which has so far been published as a preprint, showed in June that people also benefit from the omicron wave: among the over-65s, it reduced the risk of death by 81 percent and the risk of hospitalization by 67 percent .

US President Biden is not the first to be affected by the “rebound effect”. In recent months, there have been increasing reports in the United States that people treated with Paxlovid have tested positive for corona again within about five days. That is the “rebound”. That is, the effect of the drug sometimes wears off too soon. Former Harvard professor Eric Feigl-Ding warned on Twitter in May not to underestimate this effect.

Medics at the Centers for Disease Control and Prevention (CDC) also warned that Covid-19 could come back after Paxlovid.

The Covid-19 rebound is therefore characterized by

Case reports have shown that some patients with a normal immune response who have completed five days of treatment with the anti-Covid drug and recovered can fall ill again two to eight days later. Among them were vaccinated and boosted.

The representatives of the CDC wrote in May that there is hardly any reliable data so far. However, there is much to indicate that the “rebound effect” after Paxlovid causes mild symptoms. There were no reports of serious illnesses, the summary said. In addition, there is nothing to indicate that additional treatment with Paxlovid or other medication is necessary if a Covid-19 rebound is suspected.

Scientists have not yet found a clear explanation for the rebound effect. But there are different theories about it.

On the one hand, people could simply become infected with different variants of Sars-Cov-2 in quick succession. Possibly with those who escape the effects of Paxlovid.

But that may not always be the case. Another theory was put forward by David Ho, actually an HIV researcher. As “Time” reports, he had examined his own infection and other cases in his laboratory. His small study clearly showed that it was not about infections with new corona variants – i.e. actual rebounds. “It’s not reinfection with another virus. The processes are identical,” he said.

Infectiologist Bernd Salzberger gave a possible explanation for this in an interview with “Welt”: For some patients, one remedy alone is simply not enough to defeat the pathogen in the long term. In the case of HIV and hepatitis C, combinations of active ingredients have also proven to be necessary in order to sufficiently suppress the multiplication of the pathogens. The head of infectiology at the Regensburg University Hospital, for example, treated a patient himself who became positive again ten days after Paxlovid therapy and also developed symptoms. It was a woman with a very weakened immune system.

Ralf Bartenschlager, Head of Molecular Virology at Heidelberg University Hospital and President of the German Society for Virology, provided another theory: “The immune response takes quite a long time before it is strong enough for the infection to be controlled.”

In this respect, arguments seem to strengthen that the Paxlovid treatment should last longer than five days. However, there are still no official recommendations on this.

However, the “rebound effects” are no reason to forgo the anti-virus pill. Expected by many to be a miracle pill, doctors saw it early on as an “emergency nail”. The active ingredients Nirmatrelvir / Ritonavir are compatible with many other drugs such as


The list of contraindications (contraindications), such as liver failure, is long.

These could be reasons why it has not celebrated any notable triumphs in Germany so far. The Federal Ministry of Health has ordered one million doses of the drug. According to the doctors’ portal “Doc-Check”, only 30,000 prescriptions have been prescribed so far.

According to CDC recommendations, Paxlovid should still be used to treat mild to moderate early-stage Covid-19 in people at high risk of severe disease.

According to the Robert Koch Institute (RKI), the European conditional approval for the treatment of adults applies in Germany

Specifically, the RKI recommends its use

If the risk profile is very high/complex, clinicians might consider Paxlovid even with full vaccination.