What has changed, and why there hasn’t been a new variant of concern
It was 26 November 2021 that WHO declared that the world was facing a new variant of concern: Omicron. It would go on to change the trajectory of the COVID-19 pandemic.
Emerging evidence was quickly shared by scientists from Botswana, Hong Kong and South Africa and discussed in a special meeting of WHO’s Technical Advisory Group for Virus Evolution (TAG-VE).
Experts at the meeting worried about the large number of mutations present in this variant, which differed greatly from the other variants that had been detected so far. Early data showed Omicron’s rapid spread in some provinces in South Africa and an increased risk of reinfection compared to the previously circulating variants.
Just hours later, WHO declared this new variant a variant of concern: we were dealing with something new, something different, and something that the world had to quickly prepare for.
WHO’s
COVID-19 technical lead, Dr Maria Van Kerkhove, records a video announcing the
classification of Omicron as variant of concern. As soon as the variant was
classified, staff rushed to inform and prepare WHO offices around the globe
before the news became public. Photo: WHO
The
Omicron effect
Omicron was quickly identified as being
significantly more transmissible than Delta, the preceding variant of concern.
Within 4 weeks, as the Omicron wave travelled around the world, it replaced
Delta as the dominant variant.
Countries which had so far been successful
in keeping COVID-19 at bay through public health and social measures now found
themselves struggling. For individuals, the greatest price was paid by those
who were at risk of severe disease but not vaccinated, and we saw
hospitalizations and deaths rise in a number of places around the world.
This
graph shows reported COVID-19 cases in gray and deaths in blue; the impact of
Omicron is clear. While Omicron was less severe compared to Delta, there were
still a significant number of deaths due to this variant worldwide. The recent
decline in COVID-19 testing around the world has meant that we are
underestimating the true number cases, now more than ever.
By March 2022, WHO and partners estimate
that almost 90% of the global population had antibodies against the COVID-19
virus, whether through vaccination or infection.
Overall, though, this new variant caused
less severe disease than Delta on average. Scientists worked to understand why
this was so. A number of factors likely played a role. For example, the virus
replicated more efficiently in the upper airway, and population immunity had
been steadily increasing worldwide due to vaccination and infections.
While vaccines reduced the impact of
Omicron, they themselves were impacted: studies have shown that vaccine
effectiveness against infection, disease, hospitalization and death waned
(though at different rates) over time. However, protection against
hospitalization and death have remained high, preventing millions of people
from dying.
Health
worker and long COVID patient Nazibrola Bidzinashvili looks through results from
recent lab tests at her home in Tbilisi, Georgia. Georgia, like many other
countries, saw a big wave of Omicron infections, that peaked at the end of
January 2022. Photo: WHO/Hedinn Halldorsson
The
next variant of concern?
Since the emergence of Omicron, the virus
has continued to evolve. Today, there are over 500 sublineages of this variant
circulating, but not one has been designated as a new variant of concern.
So far, these sublineages of Omicron have
much in common: they are all highly transmissible, replicate in the upper
respiratory tract and tend to cause less severe disease compared to previous
variants of concern, and they all have mutations that make them escape built-up
immunity more easily. This means that they are similar in their impact on
public health, and the response that is needed to deal with them.
If the virus were to change significantly ?
like if a new variant caused more severe disease, or if vaccines no longer
prevented severe disease and death ? the world would need to reconsider its
response. In that case, we would have a new variant of concern, and with it,
new recommendations and strategy from WHO.
A lab
worker prepares samples at the National Public Health Laboratory in Singapore,
part of the network of WHO reference labs for COVID-19. Countries like
Singapore have played an important role in tracking the virus and sharing their
findings with WHO and the larger global community. Photo: WHO/Blink Media ?
Juliana Tan
WHO, together with scientists and public
health professionals around the world, continues to monitor the circulating
variants for signs of the next variant of concern. However, there is
apprehension because testing and sequencing are declining globally and the
sequences that are available aren’t globally representative (most sequences are
shared from high-income countries).
WHO and partners also remain concerned that
surveillance at the human-animal interface is limited, where the next variant
of concern could come from.
While it might be difficult to stop a new
variant from emerging, quick detection and information sharing mean its impact
on our lives can be minimized.
WHO remains grateful to public health
professionals around the world for their continued surveillance of the COVID-19
virus and the sharing of sequences and analyses.
WHO
Director-General Dr Tedros visits the Centre for Epidemic Response &
Innovation outside of Cape Town, South Africa. Scientists from the institute
were among the first to share crucial data on Omicron with WHO. Photo:
Twitter/@drtedros
Source: WHO
Date: 2022-11-25