07/08/2025  |  Bernardo Yoneshigue

https://oglobo.globo.com/saude/noticia/2025/07/08/brasil-registra-1o-caso-de-nova-variante-xfg-da-covid.ghtml 

The strain has been spreading globally, but there is no evidence that it causes more severe cases or escapes vaccine protection

Brazil has recorded its first cases of the XFG variant of Covid-19, which is becoming the most prevalent strain in the world. The strain has been identified in eight cases so far, six in Ceará and two in São Paulo. However, the available evidence does not indicate that the mutation causes more severe cases than other strains in circulation. Furthermore, it indicates that the protection provided by vaccines remains effective.

In a statement, the Ministry of Health said it is “continuously” monitoring SARS-CoV-2, the virus that causes Covid-19. Regarding the XFG cases, it emphasized that no deaths have been reported among patients and that vaccination “remains the main way to prevent severe cases and deaths.”

XFG is the latest of seven variants classified as under monitoring (VUM) by the World Health Organization (WHO). The group refers to strains that have significant genetic changes, which suggest a growth advantage over others, but whose impact is still uncertain. All strains are derived from Omicron.

According to a WHO report, XFG emerged from a recombination between two previous versions of the virus, LF.7 and LP.8.1.2. It was first identified worldwide on January 27, and on the 25th, in light of its global spread, it was defined as a VUM.

This ability to transform is what allows the virus to continue circulating in the population and gain new conditions for infection. At the same time, the clinical presentation has apparently not changed. Runny nose, sore throat, malaise, but always limited to upper respiratory infections, that is, with low lung invasion capacity, as we see with all these Omicron strains — infectious disease specialist at Einstein, in São Paulo, and PhD in Infectious and Parasitic Diseases from USP Hélio Bacha.

In the most recent monitoring, with data from May 26 to June 1, XFG accounted for 22.7% of all Covid-19 cases sequenced globally, behind only the NB.1.8.1 strain. “This is a significant increase from the 7.4% recorded four weeks earlier,” the WHO points out. Meanwhile, NB.1.8.1 fell from 29.6% to 24.9% in the last three weeks.

The proportion of XFG has grown consistently in all three regions of the world that share SARS-CoV-2 sequences, says the WHO, rising from 1.6% to 6.0% in the Western Pacific, from 7.8% to 26.5% in the Americas (AMR), and from 10.6% to 16.7% in the European Region.

In the United States, the most recent update from the Centers for Disease Control and Prevention (CDC), with data through the end of June, shows that XFG accounted for 14% of all samples analyzed, the third most prevalent strain in the country. In early May, it was only 3%.

Although with a smaller number of sequences submitted, the WHO also points out that XFG jumped from 17.3% to 68.7% in the Southeast Asia region, where the NB.1.8.1 variant had quickly become predominant at the end of March.

Risks and vaccines
Regarding the behavior of the strain, the WHO says that, considering the available evidence, the additional risk to public health is assessed as low.

“Current data do not indicate that this variant causes more severe disease or deaths compared to other circulating variants (...) Currently approved vaccines are expected to remain effective against this variant, both for symptomatic and severe cases,” the organization's report states.

The Ministry of Health emphasizes that, in Brazil, since 2024, vaccination against Covid-19 has been part of the national calendar for pregnant women, the elderly, and children. In addition, certain priority groups continue to be recommended for periodic boosters. In 2025, more than 14.2 million doses were distributed in the country.

With the new strategy, the ministry now permanently recommends one dose for pregnant women during each pregnancy and one dose every six months for seniors aged 60 or older, regardless of the number of vaccines previously received by the individual.

For children, the primary schedule should be administered between 6 months and 5 years of age with two doses four weeks apart in the case of the Moderna vaccine, or with three doses, with the second administered four months after the first and the third eight months after the second in the case of Pfizer. There is no recommendation for boosters in this age group.

For priority groups, which do not have specific routine schedules in the National Immunization Program (PNI), protection and boosters continue to be offered in Brazil under the “special vaccination” scheme. In the case of immunocompromised individuals, one dose every six months is recommended. For others, the booster is annual.

In total, the groups are: immunocompromised individuals; people living in long-term care facilities; indigenous people; riverine communities; quilombolas; postpartum women; healthcare workers; people with permanent disabilities; people with comorbidities; incarcerated individuals; prison staff; adolescents and young people serving socio-educational measures; and homeless individuals.

There is no longer any indication of a booster for Brazilians who are not pregnant, elderly, or part of one of the priority groups.

In addition, Covid-19 cases remain at a low level in Brazil. According to the Ministry of Health's dashboard, 1,260 new cases and 17 new deaths were recorded in the week of June 15-21, a decrease of 215% and 86%, respectively, compared to 3,970 diagnoses and 122 deaths in the same week in 2024.