“A corona infection protects about as well as two doses of
mRNA vaccine for around ten months. Scientists report this in a meta-study. And
emphasize: Vaccination remains the surest way to immunity.
One question has been hotly debated practically since the
beginning of the pandemic: Does infection with SARS-CoV-2 protect against
reinfection? Is Covid-19 an illness that everyone only goes through once in a
lifetime? Or does the so-called natural immunity disappear quickly after
infection?
It is now clear that anyone can get Covid-19 more than once.
As of June 2022, it was estimated that there were around 7.63 billion
infections and re-infections in the world and around half of the people had
been exposed to the omicron variant.
How long exactly the immune protection lasts, researchers
have determined in various works. Scientists are now presenting the most
comprehensive evaluation of all studies on this topic to date in the renowned
journal "The Lancet".
Studies were evaluated with subjects who had not been
vaccinated against Covid-19 or in which the vaccination status could be
eliminated as a factor. Overall, the health researchers analyzed 65 studies
from 19 countries that were published before October 2022.
According to this, infection with a variant of the wild type
or the more dangerous delta variant - i.e. before the omicron variant had
spread - provided good protection against reinfection with one of these
variants. One month after the initial infection, the protection was around 85
percent and still at 79 percent after ten months.
A previous infection with another variant protected less
well against the omicron variant BA.1, 74 percent after one month and after ten
months it was only 36 percent.
21 research papers contributed to these findings. The period
of ten months was chosen for organizational reasons, since there are few
long-term studies that have longer observation periods.
Six studies indicated that a first omicron infection can
protect against further infection with an omicron subvariant.
"The weaker
cross-variant immunity to the omicron variant and its subgroups reflects the
mutations of the virus," says Hasan Nassereldine, one of the authors of
the meta-analysis.
The mutations help the virus to bypass the existing immune
protection.
Vaccination remains the surest route to immunity
However, an initial infection still protects against serious
illness: Five studies did not focus on pure infection, in the sense of a
positive test, but on the course of the disease.
A previous infection still provided good protection against
serious illness requiring hospital treatment or death from Covid-19 even after
ten months. Before the wild type, the alpha or delta variant, this was 90
percent, with Omikron BA.1 it was also 88 percent.
The study has some shortcomings, as the authors point out.
Because it mainly deals with pre-omicron variants. But since many people have
only been infected since autumn 2022, there is still a great need for research.
The study was carried out by the so-called "COVID-19 Forecasting
Team". Many members, like first author Stephen Lim, belong to the
Institute of Health Metrics and Evaluation's, which in turn is based at the
University of Washington in Seattle. Health data is analyzed here, such as
vaccination strategies. It was founded in 2007, also through a donation from
the Bill & Melinda Gates Foundation.
The researchers also explain that the immune protection from
infection in the first 10 months is equivalent to that from vaccination with
two doses of an mRNA vaccine.
This information could influence the planning of booster
shots, they say. "Vaccination is the surest way to gain immunity,"
says Stephen Lim. Especially for high-risk patients and older people who are at
higher risk of severe disease or death. A researcher from the team emphasizes
that risks have to be weighed up. The Robert Koch Institute is also dealing
with the question of natural immunity and came up with contradictory results
last week."
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