What is a covid “rebound infection” like the one Joe Biden has

It occurs when “a person diagnosed with covid-19 in the last two weeks, after recovering, experiences a ‘recurrence’, understood as the reappearance of symptoms or a new positive result in a test,” Salvador Peiró explained to BBC Mundo, specialist doctor in public health and researcher in pharmacoepidemiology at FISABIO, a biomedical research foundation in Spain.

The occurrence of these cases was warned last May by the United States Centers for Disease Control and Prevention (CDC), a body that issued an alert specifying that the registered cases had something in common. : those affected had received Paxlovidthe drug that is being used to treat those high-risk people who have been infected with coronavirus.

“Some patients with a normal immune response, who have completed a five-day course of Paxlovid for a laboratory-confirmed infection, after recovery may experience a recurrence within two to eight days,” the CDC reported.

Thus, research points to Paxlovid, which combines two other drugs (Nirmatrelvir and Ritonavir).

Does that mean the treatment is not effective or safe? No, said Dr. Amy Barczak, who in an interview for the Harvard University School of Medicine in the US, recalled that the remedy “reduced the risk of hospitalization or death of people at risk (immunocompromised) in a 89%”.

“Antivirals change the dynamics of symptoms, they change the dynamics of the immune response and they change the dynamics of how the virus is eliminated“, he explained. “The real-world application of new drugs is more complex than clinical trials,” he added.

In short, the researchers believe that the drug may have caused the virus to trigger a secondary immune response, which manifests as mild symptoms of covid-19.

Peiró, for his part, admitted that they also observed “rebound infections” in “Paxlovid-naïve patients“. “Even in the clinical trial they appeared in people in the control group treated with placebo.”

The drug was approved by the Mexican health authorities at the beginning of the year, as well as by the Brazilian ones, and is being evaluated by those of Argentina.

Cases like Biden’s are not a cause for alarm for health authorities or scientists, at least so far. The reason? “The few data on the subject suggest that rebound tends to produce mild symptoms that do not require new treatment with Paxlovid,” Peiró explained, adding: “Rebound does not imply that the virus has become resistant to the antiviral.”

For its part, the CDC explained that the investigations, so far, have shown that, from the three days, the patient’s condition tends to improvewithout the need for additional medication.

Another reason not to be alarmed is that what happened to Biden is the exception and not the rule. A Mayo Clinic study, published last June and for which the evolution of 493 high-risk patients infected with the coronavirus and treated with Paxlovid was studied, revealed that only four of them experienced a recurrence; that is, just the 0.8%.

However, other data from the US Food and Drug Administration (FDA) raise the figure for the likely occurrence of the rebound to 2%.

Although it seems unlikely that someone who suffers from a “rebound infection” sees their life in danger, it could put the lives of others at risk. For this reason, the authorities and experts urge those affected to resume the rules of social distancing, to prevent them from infecting other people.

From the US CDC, they ask those who present symptoms of covid-19 or test positive, after apparently having overcome it, to remain isolated for five days.

At the end of the five days, the patient could return to their routine, as long as they did not present a fever during the previous 24 hours without the use of fever-reducing drugs or if their symptoms improve.

The use of a mask is recommended for 10 days after rebound.

Now you can receive notifications from BBC World. Download the new version of our app and activate it so you don’t miss out on our best content.