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Four doubts that remain about all vaccines against COVID-19 – National


Several questions about covid-19 vaccines concern scientists, governments and the general population (foto: Getty Images)

The mobilization to vaccinate the entire world population against the new coronavirus and regaining normalcy as quickly as possible has been a race against the clock.

By Friday (01/29), more than 90.4 million doses of vaccines against covid-19 had been applied, according to data from the “Our World in Data” project, linked to the University of Oxford – according to the same survey, Brazil currently has 1.6 million vaccinated.

But while countries are accelerating or starting their immunization, several questions about vaccines continue to concern scientists, governments and the general population.

It is not yet known, for example, how long the immunity offered by vaccines lasts or whether the new variants of the coronavirus, which have appeared around the world, will be resistant to immunization.

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The BBC explains four fundamental questions that still remain, two months after the start of the first immunization campaigns against the new coronavirus.

1. How long does the immunity offered by vaccines last?

How immune a person becomes after being infected with Sars-Cov-2 (the official name of the new coronavirus) or after receiving the vaccine is one of the most frequently asked questions in recent months.

One year after the start of the pandemic, the first studies on immunity in the medium and long term have been released.

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There are still no concrete answers about the period that the vaccine leaves the person immune against the virus (photo: Getty Images)
There are still no concrete answers about the period that the vaccine makes a person immune to the virus (foto: Getty Images)

According to the La Jolla Institute for Immunology in California, several of the immune responses after a person has overcome the coronavirus infection have remained active for at least six months.

It is similar to the time estimated by health officials in England, who believe that most patients who have had covid-19 are protected for at least five months.

Taking into account that it has not been that long since the first confirmed infections in the world, several scientists believe that immunity can last longer. Some even consider that stay for years.

Of course, this is not a universal rule. Each patient can develop more or less protection, and new, newly identified variants of the coronavirus are also learning to circumvent some people’s immune systems, allowing them to be reinfected by the coronavirus.

This is also being evaluated when it comes to vaccines.

“It is difficult to say how long the immunity can last (after the vaccine), because we have just started vaccination. This can vary with each patient and according to each type of immunizer. But, perhaps, it can last from six to 12 months “, says virologist Julian Tang, from the University of Leicester, in the United Kingdom, to BBC News Mundo (service in Spanish of the BBC).

Andrew Badley, a professor of molecular medicine at the Mayo Clinic in the United States, is more optimistic. “I am confident that the effects of vaccination and immunity can last for several years,” he says.

“It will also be important to analyze in detail the cases of those infected with the new variants, which were not previously known, and to observe how patients respond after vaccine“adds Badley.

The immunity obtained with the vaccine depends on the immune response of each patient (photo: Getty Images)
The immunity obtained with the vaccine depends on the immune response of each patient (foto: Getty Images)

2. To what extent does the vaccine prevent the transmission of the coronavirus?

It is possible to become infected with the coronavirus after being vaccinated. And that happens for several reasons.

The first is that the protection offered by most vaccines is not activated before two or three weeks after receiving the first dose.

“If you are exposed to the virus a day or a week after being immunized, you are still vulnerable to infection and can also transmit the virus to other people,” explains Tang to BBC Mundo.

But even if someone is exposed to the virus many weeks after receiving the necessary doses, it is still possible to be infected again.

” The available data suggest that some individuals may continue to be infected, although they get less of the virus and, consequently, become less sick than those who have never been infected or have not been vaccinated. Anyway, I think it will be more difficult for a vaccinated person to transmit the virus “, says Badley.

Therefore, there is some consensus that vaccines appear to protect a considerable number of individuals very effectively. However, it remains to be seen to what extent it prevents infection or even transmission of the coronavirus.

“It is a very heterogeneous virus and produces very different symptoms, depending on the patient. The same will happen with vaccines. Some will have a very potent immune reaction, which will prevent the coronavirus from reproducing. However, in others there will not be such a complete answer and there may be a little bit of reproduction and streaming virus “, says José Manuel Bautista, professor in the Department of Biochemistry and Molecular Biology at the Complutense University of Madrid, Spain.

Uncertainties after vaccination generate questions about the return to
Uncertainties after vaccination generate questions about the return to the “old normal” (foto: Getty Images)

3. Will vaccines protect against new coronavirus mutations and variants?

This is, perhaps, the biggest concern at the moment.

Viruses mutate constantly and sometimes become more resistant vaccination. Therefore, it may be necessary to modify them.

This fear exists with the various variants of the new coronavirus that have been identified recently, such as in South Africa and the United Kingdom, which were later found in other countries and even became dominant in some places due to their greater infectivity.

Recently, a variant was also discovered in Manaus (AM), which scholars point out to also appear to be more infectious than the strains known at the beginning of the pandemic.

It is too early to say with certainty whether these new variants are more resistant to vaccines.

This week, the Global Times, the Chinese government’s communication vehicle, said that vaccines created with inactivated viruses in the country, such as CoronaVac (from China’s Sinovac Biotech), could be updated in about two months to contain the new variants.

Moderna announced a few days ago that its vaccine continues to be effective against new variants in the United Kingdom and South Africa – that of Manaus has not, at least for now, been analyzed. Despite this, according to the company, new tests should be carried out to reinforce protection in the case of the variant found in South Africa.

Pfizer and BioNTech also ensure that their vaccine neutralizes the new variants.

“It is important to take into account that although the approved vaccines are very effective, they are not 100% effective against any variant of the virus, not even the original,” says Badley, of the Mayo Clinic.

” The protection of a vaccine will depend on how different the new variants are in Comparation the old ones, “explains Tang.

In summary, it is not yet known whether the new variants will be resistant to vaccines. However, there is a clear need for governments and health departments to monitor and identify variants emerging to assess whether available immunizers can neutralize them.

At the same time, it is already known that the faster countries are able to vaccinate their populations, the lower the chance that the coronavirus will develop new, more potent mutations – all the more reason to immunize as many people as possible. people all around the world.

The emergence of new variants of the coronavirus has caused changes in vaccine studies and has also caused new flight restrictions in many countries (photo: Getty Images)
The emergence of new variants of the coronavirus has led to changes in vaccine studies and has also caused new flight restrictions in many countries (foto: Getty Images)

4. What is the time limit for taking the second dose of vaccines?

Vaccines such as CoronaVac, Pfizer, Moderna and Oxford / AstraZeneca, for example, are administered in two doses.

In the case of Coronavac (which in Brazil is produced in partnership with the Butantan Institute), Pfizer and Moderna, the recommendation is that the second dose should be applied around 21 days after the first.

But at the end of 2020, the UK announced that it would prioritize vaccinating as many possible of people with the first dose of the Pfizer immunizer and that up to three months later would apply the second dose. In Brazil, authorities considered the possibility of also extending the period of the second dose of vaccines.

As soon as the United Kingdom announced the decision to postpone the second dose, the case sparked international debate about what would be the most recommended form of vaccination. Amid the controversy, Pfizer and the majority of the global scientific community preferred to stick to the recommendations based on what was proven in clinical trials: one dose today and the second in 21 days.

The World Health Organization (WHO) expressed its opinion on the issue and also recommended that the second dose be applied 21 or 28 days after the first. Despite this, the entity admitted that the interval between the two could be extended up to a maximum of six weeks in cases exceptional.


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https://www.em.com.br/app/noticia/nacional/2021/01/30/interna_nacional,1233740/quatro-duvidas-que-ainda-restam-sobre-todas-as-vacinas-contra-a-covid-19.shtml


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