Explained: What Is ¡®Paxlovid Rebound¡¯, The Return Of Covid-19 Infection

After routinely testing negative earlier in the week, US Vice President Joe Biden tested positive for Covid-19 on Saturday, July 30. After testing negative on Tuesday evening, Wednesday morning, Thursday morning, and Friday morning, Biden's doctor, Kevin O'Connor, claimed that above.

AP

The President's recurrence of infection is another instance of what is known as a "Paxlovid rebound" - a condition in which patients who have taken the antiviral medication Paxlovid have a recurrence of infection days after testing negative. Prior to Biden, the President's chief medical officer, Dr. Anthony Fauci, also had a Paxlovid rebound.

Why are patients experiencing infection rebound?

More than a third of Americans who have tested positive for Covid-19 this summer have been given Paxlovid, and a large number of those patients have tested back positive immediately after testing negative.

Reuters

Biden's example provides insight into why patients using Paxlovid are having an infection resurgence. The 79-year-old was fully immunised and infected with the BA.5 subvariant of Omicron, the most contagious coronavirus variant currently prevalent in the US. According to health organisations, BA.5 has the ability to bypass immune defences induced by both prior Covid-19 infection and vaccine protection.

Although Paxlovid has been referred to as the "wonder drug" against COVID-19, few medical professionals and experts have supported the usage of the antiviral medication. The medication has proven to work better on people who are unvaccinated, which is the cause.

On April 22, the World Health Organisation (WHO) said Paxlovid was ¡°strongly recommended¡± ¡ª but for patients with non-severe Covid-19 who are at highest risk of developing severe disease and hospitalisation, such as unvaccinated, older, or immunosuppressed patients.

What is Paxlovid, and how does it work?

The antiviral medication Paxlovid was created by Pfizer and comprises co-packaged nirmatrelvir and ritonavir pills for oral use. The USFDA granted it emergency use authorization (EUA) in December of last year.

Reuters

Paxlovid is given orally twice daily for five days as a combination of three tablets: two of nirmatrelvir and one of ritonavir. In total, there will be 30 tablets. Paxlovid can only be used for up to five consecutive days, according to the USFDA.

Nirmatrelvir, one of the two components of Paxlovid, blocks a viral enzyme called protease that the virus needs to replicate itself inside the host cell. Nirmatrelvir's breakdown is slowed down by the second component, ritonavir, allowing it to stay in the body for a longer period of time and at higher concentrations.

Besides Paxlovid, a second oral Covid-19 drug, molnupiravir, manufactured by Merck and Ridgeback, too received FDA authorisation in December last year. But it showed a somewhat lower efficacy in clinical trials.

Is the drug used to treat covid in India?

BCCL/Representational Image

Paxlovid is not being frequently prescribed by doctors despite being approved in India. The majority of Covid-19 cases in India have been moderate, and the government hasn't yet pushed for the usage of the drug.

Torrent Pharmaceuticals, Cadila Pharmaceuticals, Glenmark Pharmaceuticals, Sun Pharmaceuticals, and Emcure Pharmaceuticals, all of which have their headquarters in Ahmedabad, as well as Hetero Drugs and Laurus Labs of Hyderabad and Emcure Pharmaceuticals of Pune are among the 19 Indian businesses with which the MPP has signed sub-licensing agreements.