Could the Virus Rebound After Discontinuation of Pfizer’s COVID-19 Drug?

More research is needed to determine the optimal dose and duration of antiviral therapy for Omicron infection, and it is also of concern how contagious it is for people who experience a rebound in COVID-19 symptoms.

Anthony Fauci, the White House’s chief medical officer and director of the National Institute of Allergy and Infectious Diseases, revealed how he was doing after testing positive for the covid last month. Fauci said he experienced a rebound in symptoms after taking a standard course (5 days) of Pfizer’s antiviral drug Paxlovid.

The researchers suggest that more research is needed to determine the optimal dose and duration of antiviral treatment for Omicron infection, such as whether some people who start later on the drug need to take a longer course of the drug, not just 5 days. . In addition, it is worth paying attention to how contagious people who experience the rebound of covid symptoms are.

Fauci says symptoms worsened after positive retest

Fauci, 81, shared the process of his infection with the covid at a recent global health forum, and used his own statement to call on the government to more systematically study the phenomenon of the rebound of symptoms after the covid infection, so as to learn more about high-risk groups and whether The standard 5-day course of treatment with Paxlovid should be extended.

He said he had mild symptoms after contracting the virus for the first time, but given his age, he took Paxlovid and avoided hospitalization. After 5 days of taking the medicine, Fauci’s nucleic acid tests were negative for three consecutive days, but the nucleic acid fluctuated on the fourth day, and he was tested positive again.

Previously, a research team from Columbia University in the United States has found cases of nucleic acid “yin to positive” after the use of Paxlovid treatment was stopped, but said that these people may have no symptoms or only mild symptoms. The team collected at least 10 cases, and the study was published on a preprint website.

But in Fauci’s case, he said his symptoms got worse after he tested positive again. Based on Fauci’s symptoms, doctors prescribed another course of Paxlovid antiviral.

There is currently no solid data on whether Paxlovid’s antiviral drug withdrawal will lead to a rebound in the covid, only small cases that people have shared on social media. Paxlovid maker Pfizer previously said a study of more than 2,200 Covid-19 patients showed that this so-called “rebound” occurred in a minority and was observed in both the placebo and drug groups, so The company believes it has nothing to do with taking the drug.

Dr. Micheal Charness of the Boston Veterans Administration Medical Center worked with the Columbia University team to study cases of covid recurrence after taking Paxlovid. The researchers observed a decrease in viral load during treatment with the Paxlovid drug. But then in some people, virus levels began to climb again nine to 12 days after they first tested positive.

Chanes said it was unclear whether this rebound in viral load was related to stopping Paxlovid. But he found something different than his previous research. Among the 1,000 U.S. professional basketball players and related staff who did not take the drug between December last year and March this year, there was no rebound in the virus.

One possible explanation is that viral rebound is more common in older people with weakened immune systems. A virus expert from the Pasteur Institute told the First Financial Reporter: “This situation is actually caused by some people with weak immune systems, and the virus clearance time in the body is longer and caused by repeated fluctuations, which should be distinguished from reinfection. Come.”

Is symptom rebound contagious?

This situation where symptoms rebound and the nucleic acid test is positive again is often referred to as “returning positive”. “Fuyang” is different from “reinfection,” which means that genetic testing shows that when people get a second round of COVID-19 after stopping Paxlovid, it’s not because they’re infected with a different strain of the virus, and there’s no sign that the virus has A change or mutation that develops some kind of resistance to the drug.

“The possible explanation is that the antiviral drugs inhibited a large number of virus replication, but did not completely kill the virus, then the residual virus began to replicate after the drug was stopped, and the concentration became positive again after accumulating to a certain extent.” Academician of the Chinese Academy of Sciences, Chinese Academy of Sciences Ma Dawei from the Shanghai Institute of Organic Chemistry explained to the first financial reporter.

He believes that the infection pattern of the novel coronavirus varies from person to person, and many factors may contribute to the severity of symptoms, which are also related to the load of the virus.

Another concern, experts say, is whether people who experience a rebound in these symptoms are contagious. “People who experience a rebound are at risk of infecting others, even beyond the window during which the virus is usually able to spread,” Chanes said.

In the Paxlovid cases studied by Chanes’ team, a 63-year-old man infected two family members during a relapse three days after stopping the drug.

Who may be at higher risk of symptom rebound? Why does this happen? And why do some people experience worse symptoms after rebounding? Is it contagious after symptoms rebound? Researchers still know very little about these issues.

Experts emphasize that for “Fuyang” personnel with nucleic acid Ct value ≥35, the current evidence believes that they are not infectious. In my country’s ninth edition of the covid prevention and control plan, no matter whether the “Fuyang” personnel have clinical symptoms such as fever and cough, as long as the nucleic acid detection Ct value is ≥35, there is no need to track and control their close contacts.

“For Fuyang patients, it is not recommended to be hospitalized or to enter the square cabin for isolation and observation. They can participate in work and life normally.” Professor Lu Hongzhou, president of Shenzhen Third People’s Hospital, told Yicai.com. He said that the definition of “Fuyang” is still unclear. “The time of virus clearance in immunocompromised patients, tumor and AIDS patients may be longer. During this process, the Ct value will be repeated, but this is not the case of re-infection with the virus.” Lu Hongzhou said.

Huang Ailong, president of Chongqing Medical University, told Yicai.com, “Virus infection is a rather complicated process, and the replication and clearance of the virus are affected by the interaction between the host and the virus, and there are great individual differences, so it is not ruled out that a very small number of people are infected. Virus clearance takes a longer time and recurs.”

Based on existing research, the U.S. Centers for Disease Control and Prevention (CDC) believes that a rebound in covid symptoms may be a way for some people to contract the covid, and recommends that people who have symptoms and test positive after taking antiviral drugs , the 5-day quarantine should be restarted. The isolation period can be ended after the fever has subsided for 24 hours without the use of antipyretics and symptoms have resolved. The agency also recommends that people continue to wear masks for 10 days after symptoms resolve.