Experts explain how and why immunity is reduced after a vaccine

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Covid-19 vaccines were developed in record time. Operations that could take up to 10 years were completed in less than a year with the goal of halting the spread of the epidemic.

After analyzes that prove that immune systems are safe and effective against the development of serious diseases, hospitalizations and deaths from infection with the new coronavirus, scientists are focusing on another step: understanding how long vaccines protect.

The answer to this question is still unclear, but recent studies help piece together the puzzle of vaccine-induced immunity.

Adenovirus vs messenger RNA vaccines

One study Conducted by researchers at Oxford University, UK, they showed that the efficacy of the Pfizer vaccine decreased compared to the prevalence of the delta variant in the country. Vaccine efficacy after the second dose decreased more rapidly, reaching rates similar to those of the AstraZeneca immunizing agent, which showed little change in the same study.

Wide study UK, published in July, revealed that after the second dose, the Pfizer immune system showed efficacy of up to 93.7% among people with the alpha variant and 88% against the delta variant. For the AstraZeneca vaccine, the efficacy of the two doses was 74.5% for infection with the alpha and 67.% against the delta variant.

One study The publication in Science assessed the amount of antibodies produced by the Modern messenger RNA vaccine over a seven-month period. The research assessed the effects of different variants of the novel coronavirus, including the worrying variants Alpha, Beta, Gamma and Delta, which originated in the United Kingdom, South Africa, Brazil (Manaus) and India, respectively. The analysis showed that most subjects showed persistent antibody presence during this period, against all variants, although levels decreased after six months.

The results of recent studies have opened a debate about whether protection from adenovirus vaccines, such as those from AstraZeneca, Janssen, Sputnik V and CanSino, may last longer than that provided by mRNA immunomodulators, such as those provided by Pfizer and Moderna.

For specialist advice CNNIt is not possible to say that the technology used to produce the vaccines is the main reason for the difference in efficacy. The researchers explain that immunity from vaccines is a complex phenomenon that is subject to a series of variables, such as the characteristics of the vaccinated population, including age and genetic issues, in addition to circulating novel coronavirus variants.

Researcher Jorge Clil Filho, Professor at the University of São Paulo School of Medicine (USP), highlights that knowledge about immunity in relation to Covid-19 is constantly evolving.

For researcher Luis Almeida, a microbiologist at the Instituto Cuesto de Ciencia, the differences between reduced adenovirus immunity and the mRNA vaccines are likely related to the time interval between the two doses.

“What happens is that because we take longer between doses of AstraZeneca, our immune system ends up creating a longer response to fight the coronavirus. It doesn’t mean that the others lose their potency. We see that the amount of antibodies is expected to decrease, but the memory cells have to to prevail,” explains the researcher.

“We are seeing that there is faster antibody degradation with the RNA vaccines than with the adenovirus vaccines, likely due to the interval between the doses we use between them,” he adds.

According to the microbiologist, the effectiveness and efficacy of RNA vaccines is very high. “This drop in efficacy goes from 95% to about 82% when we talk about serious cases and deaths. For AstraZeneca, we saw that it was a high prevention method. The year was about 70%, to prevent fatalities and serious ones.” He explained that “cases exceeded 80% and did not We’re seeing such a sudden drop.”

Why don’t you worry about this now

Covid-19 vaccines have been developed using various technologies. Immunization devices that are considered classic, such as Coronavac, use inactivated or attenuated virus, which is unable to reproduce. Vaccines can also be made from weakened adenoviruses, a microorganism that causes colds in chimpanzees, which carries the viral genes of the coronavirus to human cells, such as those from AstraZeneca, Janssen, and Sputnik V. A third type of technology is genetic vaccines, such as those from AstraZeneca, Janssen and Sputnik V. At Pfizer and Moderna, which use the new coronavirus’s genetic material (messenger RNA or mRNA).

Although each technology takes a different approach, the goal is the same: to stimulate the production of neutralizing antibodies that recognize and eliminate the SARS-CoV-2 virus that causes Covid-19.

Types of vaccines available

Photo: Art/CNN Brazil

Moreover, the immune system response is complex and will In addition to the action of antibodies. When vaccines are administered in the body, they also play an essential role in activating other defense cells in the body, called T lymphocytes.

The cellular response generated by immunization devices also includes memory cells From the immune system that remains in the body. Thus, when an individual comes into contact with the novel coronavirus through a natural infection, they activate the production of antibodies that respond to the infection, especially preventing severe cases, hospitalizations, and deaths from the disease.

How do adenovirus vaccines work

Adenovirus is a microorganism responsible for the common cold in humans or chimpanzees. The structure of adenoviruses is used as a vehicle for transmission of coronavirus-specific viral information by the AstraZeneca, Janssen, Sputnik V and CanSino vaccines. In order for this to happen without danger to health, the production of all immunizing agents depends on the process of inactivation of adenoviruses that lose their ability to reproduce in the human body.

“The adenovirus vaccine imagines a virus similar to the coronavirus and our cells end up producing the Spike protein [principal mecanismo de entrada do vírus nas células humanas], our first reaction against this is the formation of antibodies. peak in Antibody productionIt has a natural tendency to decline,” explains Louise.

According to the researcher, the next step in the formation of immunity is to activate it cell responseWhich includes activation of the immune system’s defense cells. “The cell response takes a little longer to occur. We have cells that are able to recognize and destroy coronavirus-infected cells as well as memory cells, which store coronavirus information and start producing antibodies when they find the virus in the body,” explained Louise.

Inside Messenger RNA Vaccines

Messenger RNA (mRNA) vaccines use lipid molecules that contain information from the genetic material of the novel coronavirus. When inoculated in the body, the particles “transmit” the information of the SARS-CoV-2 virus to human cells, which begin to produce several copies.

“This genetic information is completely specific to the production of the spike protein,” Louise explains. “It’s not going to produce anything from the rest of the virus, just the tip of the S protein, which is like a key to entering our cells.”

When human cells begin to produce the spike protein, an alert appears to the immune system that begins antibody generation and later immunological memory, which is the recognition of the virus in the face of natural infection and the production of antibodies to fight it.

“Everything else in the process is exactly the same for the two vaccine technologies: it produces antibodies, and after a while they break down, it produces memory cells. If she gives a boost, she has the antibodies again and trains her memory cells more,” he says.

Vaccines are effective and safe

The researchers explained that the differences between the adenovirus and messenger RNA vaccine are specific and that these two types of immunity are effective and safe against Covid-19.

“Adenoviruses use a ‘Trojan horse’ method that will deliver the information so that the cells start producing the spike protein. While RNA vaccines don’t use any virus, they use lipid or lipid particles that provide the genetic information for the cells to start producing this piece,” Louise says.

He concludes, “These are different mechanisms for doing the same thing, and they both do it with the same premise of only producing S protein to present to the immune system so that it can learn to defend itself.”