Covid: Why some vaccines protect more than others – Época Negócios

Many countries are considering offering more vaccine booster shots (Photo: GETTY IMAGES via BBC)

BBC main subscription (Photo: BBC)

Many countries are considering providing more doses of the vaccine that protects against Covid-19 to predict the risk of new waves of infection.

The World Health Organization (WHO) has so far recommended that priority be given to the most vulnerable.

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In Brazil, the Ministry of Health already recommends three doses for the entire population between the ages of 12 and 49. For those over 50 or with an immune problem, a fourth dose is indicated.

But why does this immunizer seem to need repeated doses when protection against other vaccines can last a lifetime?

different speeds

Depending on how often you need to insert it, it depends on how fast the virus or bacterium you are fighting is changing and changing.

For example, in childhood we should all take doses of the measles vaccine, which should protect us from this pathogen for life.

The measles virus does not change much. So seeing what the body is like, it can continue to be known for decades. After all, it will remain roughly the same.

Influenza viruses, on the other hand, develop very quickly.

A vaccine given this year will train your immune system to recognize the three or four strains that are currently in circulation.

But next winter, the infectious agent will mutate so much and become so different that your body may not know it well.

This is why the flu vaccine is given every year to those who need it most, such as the elderly, children and those who are pregnant.

Half of the population in rich countries has already received a booster dose against covid.  In the poorest countries, even 1% did not have access to this third dose of immunizer (Photo: GETTY IMAGES via BBC)

Half of the population in rich countries has already received a booster dose against covid. In the poorest countries, even 1% did not have access to this third dose of immunizer (Photo: GETTY IMAGES via BBC)

Laboratory tests and infection rates suggest that the virus that causes Covid-19 has mutated enough to escape some of the protections provided by the first round of vaccines that began to be applied in 2021.

However, available immunizations remain at about 90% efficacy after a third dose of hospitalization has been applied. This rate drops to around 75% in three months, according to the UK Health Security Agency.

The South African National Institute of Communicable Diseases says it “increases the level of antibodies to strengthen vaccines”.

Ability to “remember” threats

There is evidence that our body’s ability to block the coronavirus decreases fairly quickly after vaccination or infection.

But the ability to prevent more serious illnesses lasts longer. The problem is to determine how long this protection will last, a topic that is still being studied by experts.

Although a pathogen has not changed much, the memory of the immune system can disappear as antibodies and other forms of protection begin to disappear.

And defense cells seem to remember some infections better than others, for reasons that are not yet fully understood.

Part of this is probably related to the different types of immunity we develop, according to microbiologist Simon Clarke of the University of Reading in the UK.

Antibodies produced by the immune system against some viruses after an infection or vaccine disappear fairly quickly. But this process often leaves T cells behind, which provide slower protection and longer duration. These defense units will not prevent you from catching the infection, but they will prevent you from being very ill and prevent you from being hospitalized or killed.

It also has a bearing on where these immune responses occur in the body, Clark says.

The virus that causes Covid-19 affects the nose and respiratory tract. Although there are immune responses to this part of the body, most of the antibodies produced after the vaccine are found in the blood.

So you can still catch the infection, but antibodies and other immune strategies will prevent it from “deepening” in your body, protecting you from the more serious complications of the disease.

Types of vaccines against Covid (Photo: Nature-BBC)

is a new virus

Another thing to keep in mind is that you suffer from the frequency of an infection.

You may never come in contact with tetanus, which means that vaccination is the only way for your body to know what the disease-causing bacteria are and the best way to deal with them.

After a few years, this immune memory usually disappears.

On the other hand, a common pathogenic respiratory virus called RSV, which can make children very ill, is very mild or asymptomatic in adults.

You’ve probably been exposed to it so many times that your immune system becomes very effective in dealing with it.

Before the end of 2019, no one had been exposed to the coronavirus that was causing Covid, so there was no immunity to it.

More than two years after the creation of this infectious agent, the data show that people had a close relationship with him. Studies in Brazil, Sweden, and the United Kingdom show that the combination of vaccines and infections provides great protection.

However, some scientists have expressed concern that this will lead to more people developing what is called long-term covid, with symptoms that last for months (or even years).

Do we still need reinforcements?

WHO officials said in January that “repeated booster doses of the original vaccine composition are unlikely to be adequate or sustainable.”

Many higher-income countries have offered a third dose of the vaccine to everyone.

However, in terms of the fourth dose, most of the recovery strategies have so far been aimed at groups suffering from Covid complications.

BBC footage (Photo: BBC)

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