Booster or no booster, that is the question

And the answer is related to how vaccines stimulate our immune system

By Marianne Bechara

It is a fact that certain vaccines need a booster to be more effective. This is the case of the immunogens against Covid-19, for instance. But why do some vaccines endure a lifetime, while others need to be followed by new doses?

First of all, it is important to understand how vaccines work. These biological products are developed to provoke an immune response from the body. This is why they need to contain antigens from real pathogens (virus and bacteria) or synthetic substances that imitate their components.

Because of the vaccines, our organism starts to produce more and more antibodies, getting stronger against real pathogens. Therefore, the body becomes prepared to fight actual infectious agents, protecting itself.

Many times, the immune response impelled by the vaccines is powerful enough, so one dose of the product is sufficient. However, depending on the virus or bacteria, the response may not be that strong – and, in this case, one or more extra shots are indispensable to protect the body.

When a pathogen is relatively new to scientists, such as the SARS-CoV-2 virus –responsible for Covid-19- , the challenge of creating a one-dose vaccine is immense, especially if the agent keeps mutating. At the same time, protecting the population against fatal infections is an urgent matter. Considering this reality, vaccines are developed “on-demand”, and boosters can become crucial according to the situation. However, a vaccine is only allowed to reach the market when its creators rigorously prove it is safe and effective.

As different scientific accomplishments, vaccines are developed and improved over time, with new studies, tests, and results. Since 1796, when the first immunogen was produced, many others have become a reality. According to the World Health Organization, 2 to 3 million people are saved annually by vaccines, and one of the main outcomes of immunization programs is the decrease in child and infant mortality.

Highly contagious diseases, such as polio and smallpox, are almost extinct worldwide, and mass vaccination is the reason for that. The viruses related to these illnesses are examples of pathogens that do not present extreme variations. Such stability gives scientists an advantage against these organisms, and extra shots of vaccines are not required to fight them – one dose is enough to arouse a successful immune response.

Besides the SARS-CoV-2 virus, several other pathogens suffer replications and mutations. Some of them are the viruses that cause influenza (or flu). Given the nature of these organisms, specialists recommend a new shot per year, in order to truly protect the body against those pathogens.

Either one-dose immunogens or vaccines with multiple shots are essential scientific discoveries to combat lethal viruses and bacteria. While instigating the immune response, they prepare the body for fighting infectious agents and, ultimately, save lives across the globe. Being vaccinated is an act of care.


“A guide to vaccinology – from basic principles to new developments”:

“Global Vaccine Action Plan”:

“How long do vaccines last? The surprising answers may help protect people longer”:

“Some vaccines last a lifetime – so why do we need COVID-19 boosters?”:

 “Why some vaccines last a lifetime and others don’t”:

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