Scientists evaluate the protection time of vaccines against Covid-19 – Portal Viu

Ian Haydon volunteered to test Modern’s coronavirus vaccine last year. Now, he is helping to test a new version of the vaccine, designed to combat a more contagious variant.

“A year ago I participated in the vaccine tests at Moderna to see if it was safe. Now, when I have completed a year since vaccination, I am happy to share that I just received the second dose. This experiment will show whether vaccines adapted to the new strains increase immunity and are safe, ”wrote Haydon, who specializes in communication at the University of Washington, in his Twitter account last Saturday (3).

“It is still unclear whether this new version is really going to be needed, but it is being developed and tested so that we can have an option,” Haydon told CNN by phone.

Doctors are concerned that the coronavirus that causes Covid-19 may follow the dynamics of influenza viruses, which need new vaccines every year, because both the circulating strains mutate rapidly and because the immunity of the vaccine decreases shortly. time.

Although early evidence suggests that vaccine immunity against Covid-19 provides lasting protection, vaccine manufacturers are already beginning to test and produce new versions of the immunizers targeting the most worrying variants of the virus, including strain B. 1,351, seen for the first time in South Africa, and which, in laboratory tests, carries within itself a mutation that appears to circumvent the human body’s immune response.

Pfizer’s latest report shows that people vaccinated in the African country after receiving doses of their vaccine remained protected even after the new outbreak became dominant. This corroborates laboratory experiments that showed that the immunizing agent generates an immune response so strong to the coronavirus that it also provides protection against mutations.

“The vaccine still has enough response to provide good protection,” said Scott Hensley, an immunologist and vaccine specialist at the University of Pennsylvania.

Despite this, vaccine manufacturers do not want to take risks. The research Haydon is participating in includes not only a third dose of Moderna’s vaccine modified specifically to combat the South African variant, but also a third dose of the original vaccine in some volunteers. The idea is to know if the immune response reinforced by the original third dose also guarantees an advantage and is safe.

In a report released in March, Pfizer suggests that people who received both doses of their immunizer remain with strong immune protection for at least six months. Researchers have struggled to say that this does not mean that immunity will end after six months, but that more extensive research has reached that conclusion at least for this period. Immunity is likely to last much longer, explains Hensley.

“I would not be surprised if we concluded that even a year after vaccination there will still be a strong response from the immune system”, he points out. “I wouldn’t even be surprised if we had to be vaccinated just once to do so.”

If that happens, the Covid-19 vaccine would be more like measles immunizers than flu vaccines. In the case of measles, protection lasts for life in 96% of cases.

The protection provided by Pfizer’s two doses of the vaccine still remains above 91% even after six months, according to the company. The company released more details in a statement, but not in a traditional scientific publication, and the data covers only a few thousand people. But if it persists, it will be an indication that Pfizer and Moderna vaccines elicit long-lasting immune responses, experts say.

Hensley says the technology used by both vaccines – using messenger RNA, or mRNA – is especially potent.

“The antibody responses provoked by these mRNA vaccines are incredibly high. What we know from animal testing of other mRNA vaccines is that the immune responses are very potent and do not diminish over time, ”said Hensley, whose laboratory has been testing mRNA vaccines for years.

Although vaccines against Covid-19 are still new, since the virus has only been around since the end of 2019, mRNA technology has been studied for many years, and is already used to make vaccines against influenza viruses and the causative agents of Ebola and Zika. Several studies have also indicated the same in relation to the new coronavirus.

In January 2021, a team led by researcher Alicia Widge, of the National Institute of Allergy and Infectious Diseases of the United States, wrote to the scientific publication New England Journal of Medicine to say that her research showed that the two doses of Moderna’s vaccine produced antibodies whose decrease was discreet over time.

The vaccine also caused the body to produce T and B cells, which protect the immune system, and which can keep defenses active for years. They also found that the vaccine-induced immune response was stronger and more comprehensive than the immune response that follows a natural coronavirus infection.

Another study published in February in the New England Journal of Medicine showed that blood collected from people vaccinated with the Pfizer / BioNTech immunizer continued to produce an immune response also against the South African variant.

“Although we still don’t know exactly what level of neutralization is needed to protect against disease or contamination by coronavirus, our experience with other vaccines tells us that the Pfizer vaccine is likely to offer relatively good protection against this variant,” says Scott Scott Weaver, director of the Institute of Human Infections and Immunity, Texas Medical University.

However, in March, South African virologists argued that there is growing evidence that vaccines under development do not work as well against B.1.351, and recommended that vaccine manufacturers start changing their formulas now.

Although clinical tests require frequent blood samples to check immunity, Haydon barely understands how well he is protected from the virus.

“I know that at the beginning of the trial, I and all the other participants developed neutralizing antibodies. That was clear many months ago, but the level of these antibodies and how that level has been changing over time is not something we’ve been told, ”said Haydon. “This is one of the main factors that are being analyzed in the study”.

Haydon had a strong reaction after the first round of vaccination, and also had some effects after taking the third dose. “I ended up with fever, chills, a little nausea and a headache,” he said.

Immunologists explain that this is a sign that the immune system is responding to the vaccine, although people who have been unscathed by the vaccination are also protected. In other words, it is not because someone reacted with fever that they are more protected than those who did not have any symptoms.

But Haydon knows that he cannot behave as if he is completely immune. Therefore, he wears a mask whenever he leaves the house and avoids traveling. “We are living in a world in which most people have not yet been vaccinated. The fact that I have been vaccinated myself does not change things for me, ”explains the volunteer, who said that he takes many of the same precautions as one that has not yet been vaccinated.

Although the possibility of having to look for a hospital on account of Covid-19 is very small, Haydon can still spread the virus, which is a concern. “Only very recently have data emerged that show that vaccinated people transmit the virus less. So this is also a very good discovery ”.

The information is from CNN Brasil.


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