Understand the risk that the XBB.1.5 variant can bring to Brazil

The new variant of the coronavirus responsible for the recent increase in cases in the United States has already arrived in Brazil.

The first case was identified last Wednesday (4), but it is likely that XBB.1.5 is already circulating across the country, according to specialists. She was considered the most transmissible so far by the WHO (World Health Organization).

XBB.1.5 is spreading rapidly, particularly in places where fourth dose (or second booster) vaccination coverage is low. Therefore, Brazil must be alert to a possible increase in cases in the coming days.

The report contacted the Ministry of Health and Anvisa (National Health Surveillance Agency) to find out about protection measures and strategic surveillance actions for XBB.1.5 in the country, but did not receive a response until the publication of this text.

According to infectologist and Fiocruz researcher Julio Croda, the variant is more transmissible because it presents a mutation in the S protein (or spike, used by the virus to enter host cells) that generates more affinity to the receptor in the cell, called ECA2 (converting enzyme of angiotensin 2). “This mutation leads to greater transmissibility, replicating in the human body more efficiently”, he says.

XBB.1.5 arose from a recombination of two subvariants of omicron BA.2 and reached 40.5% of virus samples sequenced in the US as of December 31, according to the CDC (Centers for Disease Control and Prevention). American.

Here, although sequence analyzes are carried out on a smaller scale, the dominant variant remains BQ.1 and its descendants. It is likely, however, that XBB.1.5 will also outperform BQ.1 given its scattering capability.

Still according to Croda, as during this holiday period many people travel abroad, especially to the US and European countries, an action at airports to monitor its spread should be implemented. “Adequate genomic surveillance helps to identify whenever necessary the introduction of new variants and monitor their circulation.”

In addition to the concern about the speed with which it spreads, the variant brings mutations with the so-called immunological escape, that is, when it manages to circumvent the protection of antibodies conferred by vaccination or previous infection.

In a study published in the scientific journal Cell on December 13, when tested with the plasma of people who received vaccination with three or four doses of immunizers or of people infected with other strains of omicron, the level of neutralizing antibodies against XBB .1.5 was greatly reduced. The same occurred when monoclonal antibodies, such as those used to treat critically ill patients, were tested against the variant, demonstrating an effect much lower than expected.

It is important, however, to remember that antibody protection is one, but not the only form of defense of the immune system, recalls Helena Lage, president of the Brazilian Society of Virology and professor at the Faculty of Animal Science and Food Engineering at USP.

According to her, vaccines, especially the bivalent ones, which contain the ancestral strain of the virus and the omicron variants in their formulation, still manage to offer high protection, especially against hospitalizations and deaths.

“The bivalent vaccine will offer better protection against this and other variants, but other forms of protection such as antibodies that are not neutralizing and cellular immunity are also important to protect patients from developing severe disease and death”, he says.

Regarding the clinical picture and symptoms, there is still no data from the CDC or the WHO to confirm whether XBB.1.5 has any alteration in relation to the other sublines of omicron. “In some places in the US there was pressure on hospitals with an increase in hospitalizations, but we still don’t have data that help us understand whether it is because of an increase in infections due to the year-end crowds or if it is related to the variant”, she explains.

Lage claims that it would be essential for the bivalent vaccines already approved by Anvisa to be offered to the population as soon as possible. “As they have a component of new variants they protect against these and others that may arise.”

The same view is shared by Croda, from Fiocruz. “The bivalents are superior to traditional formulas in terms of protecting against symptomatic disease and also in terms of the duration of this protection. So, even though we are now experiencing a drop in cases and stability in the moving average, we don’t know if it’s year-end flow, but if this variant is to replace BQ.1, as it has elsewhere, we need the updated vaccines.”