Clarín interviewed virologist Jorge Quarleri to try to understand what the coronavirus route is like in the new 2021 scenario, with a population that now has unequal weapons in the face of the pandemic.
Pablo Sigal
04/01/2021 6:01 AM
Clarín.com
Society
Updated 04/01/2021 6:01 AM
The second wave of
coronavirus is
advancing strongly in Argentina and finds the population with
unequal weapons
in the face of the new and more complex phase of the pandemic.
That, together with the variants of Covid, differentiates this epidemiological moment from that beginning of the local health crisis, in March 2020.
In the country there are currently
more than 2.1
million recovered
and
more than 3.3 million vaccinated
.
Some of them (it is not known how many) overlap, a condition that would give them an even higher level of antibodies.
It will be more and more frequent to come across someone who already had Covid or who was vaccinated.
In addition, among the vaccinated Argentines there are
more than 679 thousand
who received two doses of any of the available vaccines, while the rest of those inoculated for now continue only with the first.
All of which speaks of
various categories of immunized and susceptible
to the coronavirus.
The doubt arises in every meeting, in every social situation.
It is
the unknown of the majority
: those who have not yet been in contact with the virus and want to know if those who have already received their dose or had the disease can still infect them.
What does science say about this
heterogeneous scenario
, in which
vaccinated, convalescent and “virgins”
must live together?
Clarín
distracted Jorge Quarleri from his microscope, a biochemist at the UBA and principal investigator at Conicet, specializing in microbiology, from his microscope.
He asked ten questions and these are his answers.
Vaccination operation for people over 70 years of age in Mendoza.
Photo: Los Andes
1- It is stated that vaccinated people, despite the immunity they acquire, can infect. Why?
- The immunity achieved by active immunization (vaccine) has particular characteristics, considering the form from which it is generated.
Consider that the vaccine is administered intramuscularly and from there
"awakens" the immune response in the vaccinated
.
This immunity especially involves immunoglobulin G (IgG).
The immunity necessary so that the virus that enters the respiratory tract does not infect (that is, it does not enter and multiply within the cells of the upper and lower respiratory epithelium) must
develop and persist in the respiratory mucosa
.
The immunity achieved by the vaccine would be poor at that level (since it depends on IgA) despite the high levels of IgG achieved and that can be evaluated in the blood of those immunized.
2- Among those who have already had the disease and have antibodies, what is the possibility that they infect others?
- Even in those people who have suffered from Covid, the detectable immunity against the SARS-CoV-2 virus in the mucosa
declines over time
(because the half-life of IgA is shorter than IgG) and therefore they could receive the virus again, have it in their respiratory mucosa, and from there transmit it to other individuals.
However, the
"immunological memory"
of a past infection, or that generated by the vaccine, would not allow that person to suffer from a
severe disease
.
That is why we differentiate what it means to prevent infection from what it means to prevent disease.
Health personnel perform a swab on a Covid-19 patient in a Buenos Aires hospital.
Photo: EFE
3- What would then be the advantage of being vaccinated with regard to the transmission of the virus?
- It is very important to note that in those people who have been vaccinated,
the immune response achieved decreases
the chance of a "successful infection", that is, of reaching a quantity of important viruses in the airways and therefore, from those people the chance of transmission.
The "viral load" (amount of virus) in the vaccinated individual is expected to
be much lower
than the asymptomatic unvaccinated individual.
Therefore, it would be equally expected that the chance of contagion is greater from an unvaccinated individual.
4- How long can the virus persist in the mucosa without entering the cells and infecting?
- We do not know.
That would imply that the virus remains in the mucus that lines the cells of the respiratory epithelium.
These conditions
are "unique", in vivo and difficult to reproduce in the laboratory
.
However, due to temperature and humidity, it is a place where the virus can feel “comfortable”.
5- Can the virus stay in that "comfort" without pursuing the objective of reproducing itself?
- The virus does not think (although at times it seems that it does).
I say that this comfort implies that it
does not lose its ability to be infectious
(that is, to enter the cell and multiply within it).
On the other hand, in more inhospitable conditions for him, he loses that capacity and cannot multiply.
Now, let us bear in mind that in the respiratory tree there is, in a large part of it, a mucus covering that lines the cells of this epithelium, which in its highest part (upper respiratory tract) have in the part that faces the light a series of "hairs" (cilia) whose constant movement
"sweeps" that mucus to clean it of substances
and elements that "irritate" us (there is a cough or sneeze) so they are expelled and removed.
This "mucociliary" sweep slows down with the cold of the air we breathe in, decreases in smokers, and also
slows down with age.
A dying cell infected with coronavirus (particles in red).
6- But if the virus collides with antibodies, does it not leave that organism to look for another vulnerable target?
- Antibodies serve to
“neutralize” it
, that is, to prevent the virus from reaching the cellular receptor that allows it to enter the cell.
So in this "hand-to-hand" fight, it will be important
how many soldiers there are on each side
and how efficient they are to evade the "enemy".
That fight will last as long as the virus circulates.
7- So, is it the same for Covid to meet someone immunized than someone who is not? Are you moving "blindly"?
- Definitely.
For this reason, if we reduce the number of people "susceptible" to infection, the circulation of the virus will fall and with it
the epidemiological context
will be completely different.
It will be desirable to put so many "sticks in the wheel" that it can no longer roll.
It will cost you a lot (hopefully it will be very difficult) to
find a susceptible person
who will lose the chance to multiply.
8- Meanwhile the variants arise. Why?
- It is the counterpart of what we have been talking about.
There is evidence that the "variants" that concern us so much originated in
people with a compromised immune response
, where the virus was able to multiply "happily and openly" generating a favorable scenario for the emergence of variants.
There is a Darwinian field, where there are
"more suitable"
variants
to follow in the middle.
The coronavirus 'spike' protein has two components (shown in purple and green).
Being made up of two parts makes it 'unstable'.
The mutation makes it more stable.
9- Who would those people be punctually?
- Immunocompromised: people who due to a basic condition (transplant, cancer under suppressive therapy, infected with HIV, among other conditions) have altered the competence of their normal immune response.
In hand-to-hand fighting,
an army is severely compromised in number
and function ("few soldiers and wounded").
The army of "Sars-COV-2" will win the battle.
10- To close, how much then would the chances of an asymptomatic vaccinated person infecting, compared to another not inoculated?
- I don't know if it's defined.
I do know that in a report made by the CDC (Centers for Disease Control and Prevention) in Atlanta, USA, they have published that vaccination
protects "in the field" against infection by 90% of those who received both doses
of the vaccine (in this case speaking of Pfizer and Moderna) and 80% to those who received a dose, compared to those who have not been vaccinated.
The study involved 4,000 people belonging to Health personnel who were followed for thirteen weeks between December 2020 and March 2021.
The biochemist of the UBA and principal investigator of the Conicet Jorge Quarleri.
From the microscope to the everyday
Quarleri's explanations attempt an approach to
how the coronavirus can circulate
from those people who are vaccinated or immunized naturally.
There are studies, to which the expert refers, that indicate a significant reduction in this happening.
Although the conclusions always leave
a light of uncertainty
.
The ways of the Covid always seem to lead to the fact that, as long as the "herd immunity" is not achieved, the key will continue to be to respect the distancing measures, the ventilation of the environments and hygiene.
We are with who we are.
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Look also
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