"We
don't fully know what this variant is doing in the population,
especially since every time a new variant emerges it's not happening in a
bubble … so it's very difficult to tease apart what might be driving,
for instance, increases in hospitalizations," said Dr. John Brownstein,
an ABC News contributor and chief innovation officer at Boston
Children's Hospital.
Very little
is known about this new subvariant, but some preliminary research
indicates that it may be more immune evasive and contagious than
previous omicron variants.
"We
are concerned about [XBB.1.5's] growth advantage" in Europe and the
U.S. Northeast, said Maria Van Kerkhove, the World Health Organization's
COVID-19 technical lead, in a press conference Wednesday. XBB.1.5 had
rapidly replaced other circulating variants in those areas, she added.
Scientists still do not know if the subvariant causes more severe illness or leads to more adverse outcomes like long COVID.
Researchers
are also still studying how well vaccines will hold up against XBB.1.5.
They say the updated bivalent booster shot remains the best way to
protect yourself.
"Towards the end
of last year, the CDC came out with data showing that those who got
vaccinated and boosted with the bivalent had an almost 20-fold decreased
risk of dying and severe illness," Dr. Peter Hotez, co-director of
Texas Children's Hospital Center for Vaccine Development and dean of the
National School of Tropical Medicine at Baylor College of Medicine,
told ABC News. "The problem is that was all before XBB.1.5."
Older
adults, immunocompromised people and those with certain medical
conditions are still most at-risk for severe illness and death.