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Health Antibodies against SARS-CoV-2 remain stable, or even increase, seven months after infection
It's one of the issues at the center of the scientific debate: how long can immunity last in people who tested positive for
Covid-19
?
To date, it is not yet possible to have a definitive answer because, as
Professor Mario Clerici
, Professor of Immunology at the Milan State University and Scientific Director of the Don Gnocchi Foundation points out,
the available data are limited
because observation periods are required. . Antibody coverage appears to last
at least 9 to 12 months
.
On the other hand, the studies carried out so far coincide fairly in stating that
vaccines
are a reliable weapon, with
an efficacy ranging from 70% to 80% in the viral vector vaccines
(those manufactured by Janssen and AstraZeneca) and an even greater,
between 90-95%, in the more innovative messenger RNA vaccines (Pfizer and Moderna )
.
In addition, all available vaccines can
protect 97% of severe forms of Covid-19
and this is one of the most important aspects to significantly reduce hospitalization and mortality in
SARS-CoV-2
positive people
.
When is the vaccine effective?
The first data from which we must start is that, for the four
vaccines
authorized so far in Europe (
Pfizer
,
Moderna
,
AstraZeneca
and Janssen to which the recombinant protein
Novavax
could be added
), the response induced by the first dose of vaccine begins to be effective from 7-10 days later.
"But this is basic immunology, because every time you come into contact with a new bacteria or virus you have
a response within 7-10 days,
" explains Clerici. A study published April 27 in the
British Journal of Medicine
(BMJ) on the
Pfizer
and
AstraZeneca
vaccines
showed that
full effectiveness is reached 28 days after inoculation
and the same is true for Janssen.
The antibody response
Regarding the antibody response, three articles were published in January, in
Science
,
Science Immunology
and
Nature
, that record this trend: the
antibodies, although they persist for a period of at least six months, they decay over time
.
However, this does not mean that the human body, in the event of a new subsequent exposure to the virus, is unprotected.
The
immunological memory
based on articulated mechanisms and reactivation capacity of
B cells
and
T lymphocytes
it represents a very important resource, although it varies greatly from one person to another.
The aim of the studies was to analyze how all the components of immune memory evolved over time.
The results showed that
the response is still present eight months after infection
and that the predictable drop in
antibody titer
, already observed in previous research, is offset by the
work of memory cells
that do not leave the body defenseless.
Greater response if those who have overcome the Covid are vaccinated
But that is not enough. As Professor Clerici explains, "the latest data, also published in
Nature a
few days
ago,
are very positive because the researchers started to measure
the antibody response in both those vaccinated and those who have overcome Covid
, and it is further improved if the cured receive at least one dose of a vaccine against
Covid "
.
Comparing homologous and heterologous vaccination, it has been seen that there is a comparable persistence of antibodies in those vaccinated and in those who have passed the
Covid
.
So
the first message
we can give based on this study is:
If we vaccinate those who have passed the Covid, the response at nine months is much higher.
So better vaccinate those who have overcome the
Covid
because we give a big boost to
vaccination
.
The second message
is that
heterologous
vaccination
(that is, with two different vaccines) works better in terms of persistence power.
In the study they put the first dose of
AstraZeneca
and the second of
Pfizer
, compared them and then compared them with the double dose of
AstraZeneca
: "
well, the cross vaccine AstraZeneca and Pfizer works much better
.
"
The "memory" of plasma cells
Another more interesting confirmation about the duration of the immune response after vaccines came from another study also published in
Nature
.
"In this case they were to study
not so much the antibodies as the plasma cells of the bone marrow
, the memory cells that settle in the bone marrow and then produce antibodies. And they have seen that
the plasma cells of the bone marrow, both three months after infection and nine months after infection, they are persistent
, do not decrease, and their number is comparable to the plasma cells of the bone marrow induced by
vaccination
against tetanus.
Essentially, therefore, there is a powerful immune response at the "memory cell" level.
What can be concluded based on these data?
"The message is:
antibodies can decrease, and people worry about that, but antibodies are only produced if they are necessary
. So if nine months after I recovered from
Covid
the antibodies are lower, it is because I do not need them. However, it is necessary that there are plasma cells that reproduce the antibodies immediately after a second contact with the virus occurs. "
The Delta variant: third dose, yes or no
The question of the duration of immunity is also important in light of the advancement of
the Delta variant
.
In the United States,
some American experts propose a third dose of the messenger RNA vaccine
for people over 65 or with weakened immune systems.
Regulatory authorities in the US, FDA and CDC, consider it premature for now.
And the EMA, the European Medicines Agency, has spoken in the same direction. "At the moment, the data on usefulness and timeliness are a bit dubious," says
Massimo Galli
, head of infectious diseases at Sacco hospital and professor at Milan State University. "
Some studies say that yes, one more dose increases the expression of antibodies but does not improve their quality
in those who have already been infected.
There is still not an iota of data on those who have received two doses and we must decide what to do with them, "he concludes.
"With the data we have today,
it shouldn't be useful except in particular cases
,
"
Clerici shares.
"In immunosuppressed subjects, because the immunological memory induced by the first two should be sufficient. But it is necessary to see. Maybe not."
THE CONCLUSIONS OF A SPANISH STUDY
Pere Íñigo
Data from a
new
follow-up
analysis
in a cohort of healthcare personnel coordinated by the Barcelona Institute for Global Health (ISGlobal) indicate that the levels of
IgG antibodies
against the SARS-CoV-2 Spike protein
remain stable, or even increase seven months after infection.
The results, published in the journal Nature Communications, also support the idea that
pre-existing antibodies to
common
cold
coronaviruses
can protect against covid-19.
[MORE INFORMATION ABOUT THE STUDY HERE]
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