The most popular corona medicine: after stopping it, some are contagious again

During the pandemic, Paxlovid was the drug people were waiting for. The combination drug consisting of the drugs nirmatrelvir and ritonavir was mainly used in high-risk patients. It prevents the Sars-CoV-2 virus from replicating in the body. “Paxlovid can be used to prevent hospital admissions and serious illness in at-risk patients. Although there are still only limited effective drugs against flu, we are now therapeutically better off for Covid,” says Huldrych Günthard, an infectious disease specialist at the University Hospital of Zurich. To achieve the optimal effect, the drug should be used soon after the onset of symptoms, if possible within 5 days. In standard therapy, it is taken for five days in a row.

American researcher Mark Siedner has now conducted a new study of Paxlovid in corona patients at Massachusetts General Hospital. It shows that just over one in five people were contagious again after stopping treatment. This is called a ‘rebound’, a resurgence of the virus in the body after an initial decline.

Over the course of the study, which lasted almost a year, researchers found that 20.8 percent of those taking Paxlovid experienced a rebound of Covid-19, compared to 1.8 percent who received no treatment or a placebo. The resurgence of Covid-19 was not accompanied by the appearance of serious symptoms. The researchers write in their study that relatively mild or no symptoms mean that people can be contagious without realizing it.

It is difficult to say why a recovery at 20 percent was possible, says Günthard. It is probably a combination of causes. It was shown that rebound was more likely to occur if Paxlovid was used early. “The immune response may be less developed if the infection is blocked early,” says the Zurich infectious disease specialist. In this case, five days of treatment may be too short, causing virus replication to restart and the immune system to intervene later to develop an effective antibody and cellular immune response.

The rebound may have occurred mainly in patients with immunosuppression, whose immune system is suppressed. Such patients were likely contagious for a few days in our hospitals, which was not originally expected. This was probably not noticed, but it also had no negative consequences, as these people at risk were shielded.

It should be taken into account that the study was conducted with few patients, even if it was well conducted. To confirm the high number of rebounds, this should be investigated in a larger study, says Günthard. Other studies had shown significantly deeper recovery. Study author Siedner believes it is possible that different sampling dates could have led to different results. “For me, the study result doesn’t change anything. Clinically speaking, there is clearly a positive effect,” says Professor Günthard. “People at risk can still become seriously ill from Corona, although fortunately this is rare. Therefore, Paxlovid should still be used to prevent hospitalizations and serious illness.”

Study author Siedner also sees it this way: “The results should not deter doctors from prescribing Paxlovid. But the potential risks and benefits must be weighed for each individual.” In the trade magazine ‘New Scientist’, manufacturer Pfizer says: ‘We continue to monitor the data, but believe that a viral rebound is relatively rare and not clearly linked to a specific treatment. We remain confident that Paxlovid is clinically effective in preventing serious outcomes from Covid-19 in high-risk patients.” (aargauerzeitung.ch)