In the early days of the pandemic, it was rare to hear of
people catching Covid twice. The Omicron variant that
emerged in late November has changed that.
As new
variants have emerged, and immunity from previous infection
and immunisation has reduced, reinfection with Covid-19 is
becoming increasingly common. Some people have been infected
four times in the past two years.
A study published in
March from the South African Centre for Epidemiological
Modelling and Analysis found the risk of reinfection has
“increased substantially”. This is supported by research
from scientists at Imperial College, London that reports the
chance of testing positive again is 5.4 times greater with
Omicron than Delta.
And now there are several omicron
variants circulating around the world, all of which are
highly transmissible and very good at overcoming immunity,
whether it’s from vaccination, prior infection or both.
These omicron variants don’t just evade the protection one
may have gained from a non-omicron version of SARS-CoV-2;
they make it possible to catch the newer variants of omicron
even if the infected person has had the original omicron
variant before.
According to a report from July 8, the
Australian Health Protection Principal Committee acknowledge
that reinfections can occur as early as within 28 days and
has adjusted the reinfection period from 12 weeks to 28
days.
Of more concern however, is the theory that
reinfections may, in fact, be enhancing the disease, where a
misfiring immune response to the first infection exacerbates
the second. In dengue fever, for example, antibodies to an
initial infection can help dengue viruses of another
serotype enter cells, leading to a more severe and sometimes
fatal second infection. And in other diseases, the first
infection triggers ineffective, non-neutralising antibodies
and T cells, hampering a more effective response the second
time around.
Repeatedly catching Covid-19 appears to
increase the chances that a person will face new and
sometimes lasting health problems after their
infection.
Dr Ziyad Al-Aly, a clinical epidemiologist
and chief of research and development at Veterans Affairs
St. Louis Health Care System compared the
health records of more than 250,000 people who had tested
positive for Covid-19 one time with records from 38,000
others who had two or more documented Covid-19 infections.
More than 5.3 million people with no record of a Covid-19
infection were used as the control group.
Among those
with reinfections, 36,000 people had two Covid-19
infections, roughly 2,200 had caught Covid-19 three times
and 246 had been infected four times. Common new diagnosis
after reinfections included chest pain, abnormal heart
rhythms, heart attacks, inflammation of the heart muscle or
the sac around the heart, heart failure and blood clots.
Common lung issues included shortness of breath, low blood
oxygen, lung disease and accumulation of fluid around the
lungs.
The study found that the risk of a new health
problem was highest around the time of a Covid-19
reinfection, but that it also persisted for at least six
months. The increased risk was present whether someone had
been vaccinated or not, and it was graded – meaning it
increased with each subsequent infection.
Al-Aly said
there is this idea that if you have had Covid before, your
immune system is trained to recognise it and is more
equipped to fight it, and if you’re getting it again,
maybe it doesn’t affect you that much – but that just
isn’t true. What this study shows is that each infection
brings new risk, and that risk accumulates over
time.
Even when viruses shape shift – as influenza
does – our immune system generally retains its memory of
how to recognise and fight off some part of them. They may
still make us ill, but the idea is that our prior immunity
is there to mount some kind of defence and keep us from
serious harm. With coronaviruses, and especially SARS-Cov-2
coronaviruses, the hits just keep coming.
Already
there’s another omicron subvariant that has caught the
attention of virologists: BA.2.75 was first detected in
India in early May. Since then, it’s been found in Europe,
the United States, New Zealand and Australia. The chief
scientist with the World Health Organisation (WHO), Soumya
Swaminathan, has said that BA.2.75 appears to have mutated
in a way that could indicate “major immune escape” but
it’s too soon to know whether it will overtake BA.5 as the
dominant variant.
Graham Gordon, Founder and CEO of
Gardian, an Australian-based MedTech company that has
developed a robust, and verifiable Covid screening program
that effectively eliminates Covid ingress onsite said: “We
understand pandemic fatigue, but the virus is not done with
us.
“Unfortunately, many people are viewing the
pandemic as part of the fabric of modern life rather than an
urgent health emergency. There is a significant resurgence,
and we’re seeing increasing numbers of infections. Clearly
this is a global concern.”
Australia is nearing the
numbers of Covid hospitalisations and daily deaths it saw
during the January peak, but these are just the tip of the
iceberg. As Covid hospitalisations increase, it strains
other areas of the health system. And beyond the direct
suffering of such a massive outbreak, there are likely to be
economic disruptions as tens of thousands of people become
too sick to work.
“We are already being warned that
a new batch of variants could come out of the blue,” said
Gordon. “So, if you are at higher risk of serious illness
or just want to avoid getting sick, it’s a good time to be
wearing a N95 mask in public and using a rapid antigen test
that has a low level of detection (LoD) so that you can
detect infection prior to becoming infectious.
“The
same precautions used to prevent infection over the past two
years are as relevant today as they have always been –
wearing masks, social distancing, vaccinations, and a robust
screening process are still necessary – and they work just
as well for avoiding
reinfection.”
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