Tested negative for Covid-19, only to find you have a rebound case?

US President Joe Biden attends a meeting virtually during his isolation after being diagnosed as having a rebound case of Covid-19 on July 30 (2022). — Reuters

It's been known for several months that rebound infections can occur in Covid-19 patients who were treated with the antiviral medication Paxlovid.

Now the issue is being given renewed attention after US President Joe Biden tested positive again just days after being given a clean bill of health following a SARS-CoV-2 virus infection last month (July 2022).

According to the US Centers for Disease Control and Prevention (CDC), there isn’t much to worry about.

A relatively rare phenomenon, the so-called “Covid-19 rebound” after treatment with Paxlovid can occur between two to eight days after the patient initially tested negative again, the US health authority wrote in an advisory in May (2022).

The limited information currently available from case reports suggests that additional treatment isn’t necessary, as patients only experience mild symptoms, according to the US CDC.

However, the authority recommends isolating for five days.

Dr Stefan Kluge from Germany’s University Medical Center Hamburg-Eppendorf (UKE) agrees that Covid-19 rebound isn’t a major issue from a medical point of view.

Far less than 5% of Covid patients treated with Paxlovid experience a return of symptoms, he says.

In general, Paxlovid is recommended for patients who are not seriously ill, but are at high risk of hospitalisation, e.g. because of their age.

The pills from US pharmaceutical company Pfizer contain two active ingredients that are supposed to inhibit the multiplication of the virus in the body.

Paxlovid should be taken within five days of the onset of symptoms – in other words, in the early phase of a coronavirus infection.

According to Pfizer, this reduces the risk of hospitalisation by almost 90%, compared to a placebo.

It’s still not clear why Covid-19 symptoms can reoccur so soon after recovery from a previous infection.

Part of this is also because it happens very rarely.

According to Dr Bernd Salzberger from Germany’s University Hospital Regensburg, the fact that Paxlovid does not kill the virus could be a possible cause.

“The drug does not work like an antibiotic,” he says.

“By stopping the virus from multiplying, it gives the body time to build up its own immune protection and end the infection more quickly.”

The duration of the treatment – five days – is also quite short, he says, adding that remaining viruses might be able to start multiplying again afterwards.

In addition, it cannot be ruled out that treatment with Paxlovid could lead to the development of resistance, he says. – dpa