Vaccines: how they work and their importance for public health

Vaccines are recommended for children, adolescents and adults based on different factors, namely: age, health conditions, lifestyle, employment and travel.


The purpose of immunizations is to stimulate our body to produce antibodies against certain pathogens, mainly bacteria and viruses, but without the development of the disease.

When a person is first infected with an antigen, the immune system produces antibodies to fight the invader. However, the production is not done at a sufficient speed to prevent the disease, since the immune system does not know that invader, thus causing the development of the disease. If that organism invades the body again, the immune system will produce antibodies at a speed sufficient to prevent the person from becoming ill a second time. This protection is called immunity.

With the same antigens that cause disease, but weakened or killed, the vaccine teaches and stimulates the immune system to produce the antibodies that lead to immunity. So, if you are exposed to that organism, the sleeping memory cells ( B lymphocytes ) in your immune system will recognize you immediately and quickly start to multiply and produce antibodies. This accelerated and more intense immune response is known as a secondary response. It is faster and more effective, because all the “preparations” for the attack were made when you were vaccinated.


The feeling of malaise that can arise after immunization is common, and even expected by doctors and specialists because when the antigen is injected, the body will generate a reaction to this foreign body. The body identifies the foreign body and produces antibodies, generating an inflammatory reaction. It is this inflammatory reaction of the body that can produce fever, malaise and pain at the site, as it shows the body’s reaction.


There are 4 main types of vaccines:

Live attenuated vaccines

They contain a living but weakened form of the organism. That is, weak enough to fail to cause relevant symptoms. They are usually the best stimulants for the production of antibodies by the immune system. This type of vaccine usually requires only one or two doses and produces an immunization for many years, sometimes for the rest of your life.

Ex: BCG , chicken pox, rubella, mumps, smallpox, measles, yellow fever.

Inactivated vaccines

They contain a dead form of the organism. That is why they usually have a lower immunization capacity, requiring more than one dose to create prolonged protection. In some cases, immunization disappears after a few years, requiring the application of booster doses.

Ex: Polio, cholera, rabies, influenza (flu) , typhus, hepatitis A.

Subunit vaccines

They contain only the part of the body that stimulates an immune response.

Ex: Hepatitis B, meningitis, pneumococcus, HPV, Haemophilus influenzae .

Toxoid vaccines

They contain an inactivated bacterial toxin (toxoid). Toxoids also usually generate a weak immunization, so reinforcement is necessary after a few years.

Ex: Tetanus, diphtheria .


We know that a disease that is apparently under control can come back suddenly, because unfortunately, we have already seen it happen.

When a high proportion of the population is vaccinated, the result is the prevention of the spread of the disease – something that, consequently, gives protection to people who have not developed immunity or who cannot be vaccinated. This is called herd immunity. When it ceases to exist, there is a risk of contamination to the population as a whole.

The smallpox is the only disease that has been completely erased from the planet

Recent cases of measles – a disease that was considered eradicated from Brazil since 2016 – which recorded almost 13,500 confirmed cases and 15 deaths in the country in 2019, only reinforce the importance of immunization.

These consequences are due to the low vaccination rates in Brazil. In recent years, the target for population coverage was 95%, however, according to the WHO, in most Brazilian states, not even 75% of the population was reached.

The proportion of a population that needs to be vaccinated in order to maintain herd immunity varies according to the disease, for measles, as it is highly contagious, it is 95%.


The anti-vaccine movement emerged in 1998 in London shortly after the publication of a study by Andrew Wakefield, then released in a scientific journal that linked the triplex vaccine – used against rubella, mumps and measles – to autism. However, shortly afterwards, several other studies were published that contradicted the theory.

In 2004, the US Institute of Medicine concluded that there was no evidence that autism was related to the components of the vaccine. Then, in the same year, it was discovered that, before the publication of his study, Wakefield had applied for a patent for a measles vaccine that would compete with MMR, something that was seen as a conflict of interest.

In addition, a Wakefield assistant said that in his study, the doctor manipulated information from children to force the link between the vaccine and autism. Thus, in 2010, the United Kingdom’s General Medical Council judged Wakefield “unfit for the profession”, describing his behavior as “irresponsible”, “unethical” and “deceptive”. Shortly afterwards, Lancet, the periodical that had made its study public, retracted the publication, saying that its conclusions were “totally false”.

The World Health Organization (WHO ) considers the issue of anti-vaccine movements so worrying that it has listed it as one of the top ten threats to global health in 2019.


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