Why You May Need To Wear A Mask Even After A Covid-19 Vaccination

Although there are particularities depending on the type of vaccine and the type of disease, the general mechanism of operation of a vaccine is always the same: it introduces a particle – called an antigen – into the body that produces an immune response in the body and turns it into a preparation. to face an attempt to contaminate the body if it comes into contact with the virus in the future.

This antigen can be an inactivated (killed) virus, a weakened virus (which cannot make someone sick), it can be a part of the virus, some protein that looks like the virus, or even a nucleic acid (such as RNA vaccine).

The antigen provokes an immune response, that is, it makes the body able to recognize this virus and produce antibodies to fight it, explains infectious disease doctor Jorge Kalil, professor at the Faculty of Medicine of the University of São Paulo (FMUSP) . .

The next time you come into contact with that virus, the body will remember how to fight it and can deal with the threat quickly and efficiently, preventing the virus from contaminating the body.

This response is called the adaptive immune response and is specific to each virus. “It is a response that takes a little longer, it takes at least two weeks before the body learns to recognize and fight the virus with the help of the antigen”, explains Natália Pasternak.

So after getting vaccinated, be it against coronavirus or any other disease, you’re only really protected after a few weeks, the scientists explain. It is as if the body needs time to “process” that information and react appropriately.

In an unvaccinated person, Sars-Cov-2, the virus that causes covid-19, enters the cells of the respiratory system and begins to use them to produce more viruses. It is as if he produces “zombie cells” that work for him.

The first immune response produced by the body after vaccination is the production of antibodies, which bind directly to the virus and prevent it from entering the body’s cells and using them to produce more virus, explains Pasternak.

That is, in an immunized person, the body already knows the virus from the vaccine and from the moment the pathogen enters the body, antibodies are released that prevent contamination of cells.

But there is a second type of immune response, called a cellular response. “They are cells, called T cells, that do not bind to the virus, but recognize when a cell is contaminated with the virus and destroy it,” explains Pasternak.

That is, if a virus can escape the antibodies and contaminate any cell in the body, the T cells function as “hunters” and destroy this “zombie cell”, preventing more viruses from being produced.

The cellular response takes a little longer than the response through antibodies, another reason why immunization is only completed a few weeks after receiving the vaccine, explains Jorge Kalil.

“After 15 days, we already expect a cellular response from the immune system,” says Kalil.

In addition to the time it takes for the body to develop the immune response, in the specific case of coronavirus, another issue requires maintaining protective measures for some time after vaccination: most vaccines that are being developed against the disease require two doses to achieve the expected effectiveness.

Two doses will be needed for the four vaccines that have already proven effective: Pfizer’s, Moderna’s, Oxford / AstraZeneca’s, and Sputnik V. This also holds true for Coronavac, which is being developed by the Butantan Institute in collaboration. . with the pharmaceutical company Sinovac.

“In the case of the vaccines that we will probably have available against the coronavirus in Brazil, the orientation will be to take the first dose, wait a month, return to the clinic, take the second dose and maintain all the care against the pandemic, such as isolation social and use of masks, for at least 15 days. Only then will you be protected, according to the efficacy of each vaccine ”, explains Jorge Kalil.

The first dose, explains Natália Pasternak, is what scientists call the main booster. “It’s like waking up the body to the virus, giving the immune system a ‘kick start’. The second dose generates a better immune response,” he explains.

The amount of dose required varies widely with the vaccine formulation. The yellow fever vaccine, for example, only requires one dose.

Among the 200 vaccines in development against the coronavirus, there are some that would be in a single dose, but are not in as advanced stages of development as those that will require two doses.

“When you can do it in one dose it is better, because from a public health point of view, it is a challenge to get people to go back to the clinic to take the second dose. People forget, they think it is not necessary.” explains Pasternak.

Combining the time it takes between doses and the time it takes the body to produce the immune response, it will take at least a month and a half for someone who has been vaccinated to be considered immunized.

But even after that, it will take time for life to return to normal, and until the majority of the population is vaccinated, the guidance is that even vaccinated people stick with the measures.

No, the scientists explain, because if there is good vaccination coverage, a vaccine can greatly reduce the circulation of the virus through so-called herd immunity.

It is true that individually, if only one person takes it, no vaccine is 100% effective, and this is also true for covid-19. The Pfizer vaccine, for example, is 95% effective, based on the results of the third phase of testing.

This means that there is a 5% chance that that specific vaccine will not produce an immune response in the body of the vaccinated person. But then, how do vaccines prevent the virus from spreading if there are some people who can become infected?

“The vaccine works through herd immunity, which is a concept of a vaccine”, says Jorge Kalil.

The virus is transmitted from person to person, explains the doctor, and in order to spread it, it is necessary to find people who are susceptible to the disease. “The vaccine reduces the number of susceptible people, so significantly that the virus cannot find more circulation and is contained. This is how we eradicate smallpox ”, explains the doctor.

Herd immunity is important not only because vaccines are not 100% effective, but because there are many people who cannot even take the immunizer.

“There are people who cannot receive it because they are not old or because they are not part of the vaccination program; vaccines against the coronavirus have not yet been tested in children, in pregnant women, ”explains Kalil. People with a disease that compromises their immune system also cannot be vaccinated.

“When there is minimal vaccination coverage for the population, these vulnerable people are protected by herd immunity,” explains Kalil.

In the case of the coronavirus, the WHO estimates that the vaccination coverage necessary to stabilize and contain the pandemic is 80% of the population, ideally 90%.

To get an idea of ​​the importance of vaccination coverage, when there was a drop in measles vaccination coverage, from 96% in 2015 to 86.5% in 2018, there were several outbreaks of the disease across the country. .

That is why it is important that even those who have already been vaccinated and have waited a month and a half, do not abandon measures against the pandemic.

In the case of vaccination against the coronavirus, it should take some time before the vaccine reaches the majority of the population, even after approval by Anvisa (Sanitary Surveillance Agency). The production of millions of doses is not something that happens overnight. There are also issues such as government agreements with pharmaceutical companies, the waiting list in various countries, the difficulty of distribution and storage (some vaccines must be stored at temperatures well below freezing), etc.

The Ministry of Health has a list of people who will be given priority to receive vaccines. The first should be people over 80 years old and health workers. Then, the elderly between 60 and 79 years old and people at risk, such as those with chronic respiratory diseases, should receive the vaccine. There are still three other priority groups and only then will the general population be vaccinated.

“It is important that whoever receives the vaccine first maintains measures to combat the pandemic because, even after a month and a half, even if he is immunized, there is no guarantee that he cannot be a vector of the disease until there is herd immunity.” Pasternak says.

The scientist explains: the vaccines tested so far prevent the virus from reproducing in the body and making the person sick. But there is no evidence, for now, that shows that this person will not transmit this virus, which is being fought by antibodies in their body, to other people.

The summary of all this is that, even if you have already taken the two doses of the vaccine, you have waited another 15 days, you have to wait until the majority of the population is vaccinated so that life returns to normal, advises Jorge Kalil. This is as much to protect yourself, if you are in the small group of people for whom the vaccine will not have an immunizing effect; and protect others, until the herd immunity generated by extensive vaccination coverage is able to contain the pandemic forever.

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