Mallorca "We have seen and read things that say that they are happening here and that they are not true"
Coronavirus "The Delta variant affects more children and adolescents"
Live Last minute on the coronavirus
With the arrival of new variants of the coronavirus and the uncertainty about the permanence of immunity, some sectors claim the need to reinforce people's immune responses with new doses of vaccines. There are no conclusive studies on the subject, but discovering how long immunity lasts,
both after vaccination and after infection
, is essential to be able to manage the epidemic in the coming months.
According to various studies, immunity could last at least eight months;
other research goes further and
considers that immunity could be valid for one or several years
.
Two works pointed out by
The New York Times
, reveal that immunity could last for years and that most of the people who recovered from the infection and, therefore, immunized, would not need new doses or immune boosters.
On the contrary, those vaccinated who have not had the disease would have
the need to reinforce their immune system from time to time
.
As well as the minority of people who, despite being infected, have not developed an adequate immune response.
B cells
The answer is due to the fact that memory B cells, responsible for generating a solid immune response,
allow the development of neutralizing antibodies if the body comes into contact with the virus again.
Both works have examined the data of people infected a year ago.
According to the study published in the journal
Nature
, these cells housed in the bone marrow
retain a memory of the virus
and are able to produce antibodies when necessary.
The other study published (not yet reviewed) on the
BioRxiv
website
concludes that memory B cells develop up to 12 months after infection.
Studies attenuate the fear of a transient immune response, as in the case of coronaviruses that cause the common cold.
"Coronaviruses change in a significant way in a short time,"
Scott Hensley, an immunologist at the University of Pennsylvania,
told
The New York Times
, "and the reason we continually catch common coronaviruses could actually
have more to do with mutations than immunity. "
Bone marrow
B cells proliferate and produce antibodies in large numbers upon first encounter with the virus.
After the acute infection has resolved,
a small number of cells establish themselves in the bone marrow
, constantly producing antibodies.
To examine B cells specific to the new coronavirus, researchers led by expert Ali Ellebedy of Washington University in Saint Louis,
have analyzed the blood of 77 people over three-month intervals.
Only six of the 77 had been hospitalized due to Covid-19;
the rest had mild symptoms.
Volunteers' antibody levels decreased rapidly four months after infection
and have progressively decreased in subsequent months
.
The decrease in antibodies is interpreted by scientists as a sign of the drop in immunity, but in reality it is not a worrisome data,
but an expected biological event
.
Antibodies at the blood level decrease drastically over time, while memory B cells
remain inactive in the bone marrow to intervene
when necessary.
Powerful response
To understand the mechanism, Dr. Ellebedy's team has analyzed 19 bone marrow samples seven months after infection.
In 15 of them, memory B cells were detected
, but in the other four there were very few or were non-existent. Not everyone who passed the covid therefore developed adequate immunity. This is why vaccines are so important.
Five of the participants donated marrow again months later, at least twice:
the researchers have found that the number of memory B cells remains stable
over time. Research is very important because it is very difficult to obtain bone marrow samples for study. Building on other important work in 2007, which discovered how the B cells of various pathogens survived for decades, scientists were wielding the possibility, confirmed by the two studies, of developing long-lasting protection against Covid-19.
According to Miche Nussenzweig, an immunologist at the Rockefeller University in New York, who led the study published in BioRxiv,
memory B cells produce a response to Sars-CoV-2 infection
and potentiated with vaccination are potent against the variants.
Cell development
The team has examined how memory B cells mature over time.
Researchers have analyzed the level of antibodies in the bloodstream of 63 people one year after becoming infected.
26 had been vaccinated with one or two doses of Pfizer or Moderna.
Neutralizing antibodies, necessary to prevent reinfection, have been found to
remain unchanged between 6 and 12 months,
while secondary
antibodies
decreased rapidly.
Scientists have observed that memory B cells continue to develop for at least a year. One year after infection, the neutralizing antibodies of those who have not been vaccinated, however, lost
their efficacy against the numerous variants examined, in particular the South African one
. Those who had received at least one dose of the vaccine developed a very strong neutralizing response and
a high level of antibodies thanks to the work of memory B cells
, which were reactivated with the vaccine. The result of this research suggests that people who managed to pass the coronavirus and were subsequently vaccinated maintain high protection, also against new emerging variants.
According to the authors, this mechanism is not proven to work only with vaccine-induced protection.
Immune memory is likely to develop more efficiently in the event of a natural infection
.
"Therefore, it is possible that those who have not had the Covid and have been vaccinated
could need booster doses
. We will know soon," concludes Nussanzweig.
According to the criteria of The Trust Project
Know more
Coronavirus
Covid 19
Masks
Lockdown
De-escalated
Unconfined
New normal
Sprouts
AIDS and hepatitis
Infectious diseases
HBPR
Energy Electricity and fuel have already skyrocketed 37 euros per household in just 15 days
The incidence of the coronavirus climbs to 117.17 and shoots up to almost 300 among young people (12-29 years)
The incidence of the coronavirus in Spain falls below 100 (98.78)
See links of interest
Work calendar
Home THE WORLD TODAY
Best Universities
Stage 6 of the Tour, live: Tours - Châteauroux