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The subvariant of omicron,
BA.2,
informally called
omicron 2
, is constantly on the rise around the world.
Its presence has already been confirmed in 43 countries and, according to the latest monitoring by the
World Health Organization
, it represents 21% of
omicron
cases .
Ten countries already have
omicron 2
as the predominant variant, including
China
, the
Philippines
,
India
,
Nepal
and
Denmark
, where it reaches 66%.
In southern Europe at the moment it represents only 3% of cases.
Is it more or less transmissible than omicron?
Early studies indicate that
BA.2
is more transmissible than
BA.1
.
Estimates in
Denmark
and
the United Kingdom
indicate that
omicron 2
is between 30% and 50% more transmissible than
omicron
.
In a Danish study with 8,000 families, unvaccinated cases infected with
BA.2
were found to be more likely to transmit the virus to family members than those infected with
omicron
.
However, even those who had completed the vaccination course were more vulnerable to the BA.2 variant than to BA.1.
Omicron 2
grows both in countries where there is a decrease in the pandemic wave and in those where there is growth, and this data supports the hypothesis that the reason for the increase in diffusivity is due more to greater transmissibility than to immune evasion of vaccination or previous infection.
A laboratory study confirms this hypothesis.
Is the disease more serious?
There is currently limited evidence on possible differences in disease severity induced by
omicron
and
omicron 2
variants .
In
the UK
, where
omicron 2
has grown steadily in recent weeks, there has been a decline in hospitalizations and deaths.
An analysis from
Denmark
showed no difference in the risk of hospitalization between people infected with
omicron
or
omicron 2
, although there has been an increase in the number of hospitalizations and deaths in the country since the latter became dominant.
However, the variant does not appear to cause more severe disease, even in children.
In
Nepal
, where
omicron 2
prevails with very high percentages, the number of hospitalizations, even in intensive care, is decreasing.
The same is true of
South Africa
, where
omicron 2
is 86% and hospital admissions continue to decline.
A Japanese laboratory study published in preprint just three days ago concludes that it could cause more severe illness.
The researchers infected hamsters with
omicron
and
omicron 2
.
Animals infected with the second variant became more severely ill and had more impaired lung function.
According to Japanese scientists,
omicron 2
has virological and pathogenic characteristics that distinguish it from the previous strain and should therefore be considered a variant of concern in its own right.
Their analysis also determined that the reproductive rate of
omicron 2
would be 1.4 times higher than that of the previous strain, and that the new
omicron
subvariant appears to be more replicative in human nasal epithelial cells than the original.
Are vaccines effective?
Several studies suggest that
omicron 2
can easily overcome immunity induced by vaccination or previous infection with other variants, but not much different than what omicron is already doing compared to the variants that preceded it.
In fact, some analyzes carried out in
the United Kingdom
and
Denmark
even show a greater capacity of the vaccine to prevent
omicron 2
than 1.
Data from
the UK
indicate that the administration of a booster dose two weeks after the second dose of the vaccine showed an efficacy of 63% in the prevention of symptoms of the disease caused by
omicron
and 70% in the case of
omicron 2
, but the efficacy data decrease over time in both variants.
However, the results of the studies carried out so far are not unequivocal.
Work led by virologist
David Ho
of
Columbia University
in New York City confirmed that
omicron 2
and
omicron
have similar abilities to resist neutralizing antibodies in the blood of people who had been previously vaccinated or infected.
But Ho's team reported that genetic mutations unique to
omicron 2
affect how some antibodies recognize the variant.
In fact, some antibodies would be less effective in neutralizing the second, while, on the contrary, another type of antibody tends to be more active with it.
"It is unlikely that there are any higher risks with
omicron 2
than with
omicron
," he says.
Could omicron 2 lead to a new pandemic wave?
Scientists believe that omicron 2
is unlikely to
trigger a new major wave of infections, hospitalizations and deaths, following the wave of
omicron
.
However, the variant could create greater problems in countries with low vaccination rates.
" Omicron
's sister
could prolong the pandemic wave. But our data suggests there will not be a new surge,"
Dan Barouch
, an immunologist and virologist
at Beth Israel Deaconess Medical Center
in Boston, an author of a study , tells
Nature .
In his case, the neutralizing antibodies induced by three doses of the
Pfizer
vaccine proved slightly better at preventing the original variant.
"But this small difference in immunity avoidance is unlikely to explain the increase in BA2 around the world," Barouch says.
Can omicron 2 infect those who have recovered from omicron?
It is not yet clear whether the new variant is different enough to cause reinfection in people who have been infected with
omicron
.
We know that those who have recovered from
omicron
can feel quite comfortable because contagion with the same variant is considered highly unlikely as specific antibodies have developed.
But
omicron 2
is not the same virus: it shares 38 mutations with the original variant but has an additional 27 unique mutations.
Researchers in
Israel
have identified a handful of cases in which people cured of
omicron
subsequently became infected with its sister variant.
The
State Serum Institute
in
Copenhagen
has launched a study to determine how often these reinfections occur.
Troels Lillebaek
, leader of the investigation, says that he would be surprised to discover that there is no protection.
What is the time of onset of symptoms?
From a preliminary
UKSA
survey based on monitoring the situation in
the UK
, the median time to onset of symptoms would appear to be half a day shorter for
omicron 2
than for
omicron
, with a median period of 3.27 days compared to 3.72 days, respectively.
With
Delta
, the interval between infection and onset of symptoms was approximately four days.
The shorter incubation time could contribute to the increased growth rate of
omicron 2
.
Do omicron 2 treatments work?
A preliminary laboratory study found that
omicron 2
is resistant to the monoclonal antibody
sotrovimab
, the only one so far believed to be effective against
omicron
.
On February 9,
Vir Biotechnology
, which together with
Glaxo
produces the drug, declared that experiments carried out by the pharmaceutical company and not yet released, suggest that the monoclonal is also effective against the new variant.
There is no data yet on the effectiveness of the antiviral.
Do the tests detect omicron 2?
Omicron 2
has also been defined as "invisible" because it is difficult to identify, since it does not have the characteristic "S gene deletion" of
omicron
: to find it, therefore, it is necessary to sequence all the samples and this implies a capacity of laboratory that not all countries have.
The lack of the S gene, on the other hand, is what allows us to suspect that a sample belongs to the
"classic" type
omicron variant directly from the unsequencing test, which is done later.
Conforms to The Trust Project criteria
Know more
Omicron variant
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HBPR
HealthThe perfect storm of infections Omicron, third doses and Covid passport: keys to understanding the peak of infections
CoronavirusWhat is known about the silent sister of ómicron?
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CoronavirusReinfection with omicron: What chance do I have of being infected again, and how long after?
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