Dr. Anthony Fauci, the top infectious disease expert in the US and chief medical adviser to President Joe Biden, recently shared that he has been struck by COVID rebound after a course of Pfizer's antiviral drug Paxlovid.
According to Bloomberg, the 81-year-old was fully-vaccinated and twice-boosted but still contracted COVID-19 earlier this month and was prescribed Paxlovid due to his age, which puts him at high risk of developing complications. He said in an interview that his current rebound is worse than his first round with the disease.
Taking Second Pfizer Paxlovid Course
Fauci has been tested positive for COVID-19 weeks ago with mild symptoms and was prescribed a five-day course of Paxlovid. He felt quite well during that time and tested negative three consecutive days after the first course of Paxlovid. But his fourth test came back positive and he experienced a COVID rebound.
He then felt poorly and worse than in the first round. Paxlovid is an antiviral drug from Pfizer approved by the US Food and Drug Administration (FDA) to treat mild to moderate COVID-19 in those at risk of developing severe illness. The Centers for Disease Control and Prevention (CDC) has warned of a rebound that seems to be rare and yet is increasingly becoming more common.
COVID rebound usually occurs between two to eight days after initial recovery and is likely caused by the "natural history" of the SARS-CoV-2 virus. Health officials said that it might occur in some people regardless of Paxlovid treatment or vaccination status, ABC News reported.
Fauci was prescribed another course of Paxlovid and reported to feel better. However, CDC says in their report that there is no evidence that an additional Paxlovid course is needed following a COVID rebound. Moreover, FDA says that there is no evidence of benefit for a longer course of treatment in patients with recurrent COVID-19 symptoms after an initial course of Paxlovid.
CDC recommends following its guidelines on the isolation of at least five days and taking extra precautions to prevent transmission. They can end their five-day isolation if their fever and symptoms disappear after 24 hours. Wearing of face mask is also recommended, especially after rebound symptoms occur.
How Common is COVID Rebound?
For now, it is unclear how and why COVID rebound happens even among those who received complete vaccine doses. But the CDC says that COVID rebound is usual in those who took Paxlovid.
That supports initial clinical data of Pfizer on Paxlovid that shows about 1% to 2% of both the treatment and placebo groups had a recurrence of COVID-19 symptoms, ARS Technica reported. As more people take Paxlovid, health experts expect more post-Paxlovid rebounds.
Investigations are underway to find what causes these rebounds, one of which is NIAID's report that suggests rebounds are partly caused by the immune system getting reignited as the body clears dead cells and viral debris from the initial infection. The study did not find evidence that SARS-CoV-2 is mutating to fight Paxlovid or that the immune system failed to work against the virus.
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