Decades of scientific work allowed the development and production in record time of vaccines against COVID-19.




Vaccines are tools, safe and effective, that protect people from contracting infectious diseases by stimulating the production of our defenses, which are the antibodies. They also help to prevent the transmission of these diseases in the community, thus representing one of the most significant achievements for public health.


Pathogens, such as viruses and bacteria, trigger a specific response in our immune system, which culminates in the production of antibodies that support the elimination of the infectious agent. Vaccines contain weakened or inactive parts of a particular organism that we want to fight, or instructions for the production of these antigens by our own cells, triggering the production of antibodies and a memory system.


If in the future the person comes into contact with the real disease-causing virus or bacteria, the immune system will “remember” them and act quickly, protecting the person from the disease - the person is immune. Immunity generally lasts for years and sometimes for life. But the duration of immunity varies depending on the disease and the vaccine.


The digital campaign Conversations with Scientists ran from April 20 to 30, 2021. It promoted more than 328 sessions held with the support of more than 120 scientists from 20 national institutions.


The initiative provided sessions in Portuguese and English for more than 8856 participants, completely free of charge. It reached diverse audiences, having received participants from north to south of the country, the islands, East Timor and São Tomé and Príncipe.


Each session stimulated dialogue on issues related to the development of vaccines against Covid-19, explaining and deepening the historical framework around the development of science, which allowed to guarantee a safe and effective vaccination campaign in record time.


It was within the scope of these online sessions that most of the content on this page was developed, in close collaboration between several scientists, from various national institutions in the area of ​​Health Sciences.


The purpose of a vaccine is to “teach” the immune system to recognise an infectious agent, and to stimulate our immune system to produce antibodies against that micro-organism. There are many ways to develop a vaccine, but they all share this common goal. Vaccines help our body acquire a sustained defence against different diseases, including COVID-19.


Before a vaccine is authorised, and regardless of the technology used to produce it, it must undergo a rigorous evaluation process to assess its safety and efficacy. This close scrutiny helps distinguish vaccines as one of the most life-saving medical interventions in human history, by providing effective protection against several infectious diseases that have caused countless deaths in the past.

Vaccination is an essential public health tool. Vaccines are safe, effective and prevent severe disease .

Antibodies work by recognising specific parts of each pathogen, such as proteins on the cell surface – markers we call antigens. When our body is first exposed to a particular antigen, the immune system produces antibodies specific to it. Adapted from World Health Organisation


When someone is vaccinated, they will most likely be protected against the target disease. A small number of people cannot be vaccinated – for example, transplant patients, the immunosuppressed, some chronically ill, and also new-borns. 


The reason why these people cannot be vaccinated is related to the functioning of their immune system, or because they may develop severe allergies to some of the fluids used as a base to dissolve the vaccine, the excipients.


However, vaccination not only protects those who are vaccinated, but also those who cannot receive the vaccine. When much of the population is already immune, the infectious agent has difficulty spreading in the community and the likelihood of infecting people who cannot be vaccinated is then more limited. This phenomenon is called herd immunity.

What is herd immunity?


i3S - Instituto de Investigação e Inovação em Saúde (Institute for Research and Innovation in Health) April 2020



Different pharmaceutical companies, businesses and scientific institutions have been working on the development of various vaccines against covid-19. They all work on the same target: a protein that only exists in coronaviruses like SARS-CoV-2. This protein, called Spike, is found on the surface of the virus and acts as a key for the virus to enter our cells. By itself, this protein is not able to cause disease. Since our body recognises Spike as an external element, what vaccines do is induce the production of antibodies against it, blocking this “key”, and thus preventing the virus from infecting our cells and multiplying.

Vaccines against COVID-19 are therefore designed to provoke the production of Spike, or to insert this protein (or parts of it) into our body, triggering the production of antibodies and immune system cells in response. Some of these cells stay in our body's “memory” and, if we become infected, they are quickly recruited to fight SARS-CoV-2. Another advantage of Spike is that it is the protein that triggers the most potent antibody production.

Although all available vaccines have been designed for this target, their development was based on different technologies. There are three main groups of COVID-19 vaccines, two already approved – Viral Vector and RNA – and one that is close to approval - Subunits.


Viral vector: these vaccines use another modified virus – adenovirus – as a vehicle to carry into cells the genetic instructions that will lead to the production of the 'Spike' protein.


RNA (ribonucleic acid): these vaccines use the genetic material of the virus which has the instructions to make the “Spike” protein.


Subunits: these vaccines the “Spike” protein

Ciência Viva, with Paula Alves (IBET e ITQB Universidade Nova de Lisboa) - January 2021



What is Basic Research?

It is all research that seeks to produce knowledge, for knowledge's sake, without aiming at a practical application, a solution to a problem. Basic research is that which seeks to explain the world around us and which is driven by the curiosity of scientists. Thanks to this kind of research, we are now able to find quick answers to new problems, as is the case of the emergence of the new SARS-CoV-2 coronavirus.

The vaccines against COVID-19 were first presented about 9 months into the pandemic. But how was this possible when, on average, it takes several years to develop new vaccines ?


There are a handful of reasons:


Reason 1:  


The essential building blocks that enabled the rapid production of the vaccines against COVID-19 resulted from the accumulation of knowledge generated over decades.


Over several years, many discoveries were made in different laboratories, sometimes in parallel, thanks to the research developed by numerous groups of scientists spread all over the world.


The lines connecting these discoveries have crisscrossed, and collaboration and sharing – inherent properties of the knowledge construction process – were crucial for all these pieces to be ready to use when SARS-CoV-2 caused the pandemic in March 2020.


Without these paths taken, which are more like a maze, it would never have been possible to produce the vaccines against COVID-19 in record time.

Reason 2: The accumulated experience on vaccine production against other diseases.


Reason 3: Because of the severity of the diseases caused by SARS-CoV and MERS-CoV (both from the coronavirus family), many laboratories had already started developing therapies, identifying antibodies and testing vaccination strategies against these viruses.


Reason 4: Vaccine production platforms have undergone extraordinary advances.


Reason 5: During clinical trials, three factors were instrumental in shortening the production time of the vaccines against COVID-19.


- From February 2020, trials began in Phase II; safety trials (Phase I) were not necessary, as they had already been conducted with other coronaviruses at the time of the SARS-CoV-1 (SARS) epidemic that broke out in Asia in 2003. The direct move to Phases II and III was also only possible because funding was already secured.


- The efficacy of a vaccine can only be tried by testing it on a large number of infected people. In this case, the spread of the virus was so fast that it was soon possible to test the various vaccines on tens of thousands of volunteers, and determine that they were effective in protecting against the virus.


- The Regulatory and Approval Phase ran in parallel with Phase III clinical trials.

Phase I Safety trials. What are the side effects and how the treatment is eliminated by the body.


Phase II Trials to determine the right dose of treatment based on the induced immune response, such as the amount of antibodies produced.


Phase III Trials to evaluate efficacy. Thousands of people in areas with high transmission rates are vaccinated to assess whether they are protected against the virus.

iMM - Instituto de Medicina Molecular João Lobo Antunes (Institute of Molecular Medicine João Lobo Antunes), with Bruno Silva Santos, iMM immunologist - january 2021

iMM - Instituto de Medicina Molecular João Lobo Antunes (Institute of Molecular Medicine João Lobo Antunes), with Miguel Prudêncio, iMM parasitologist - january 2021


Are the vaccines safe?

Yes, the vaccines are safe, as shown by the research leading to their approval. All vaccines go through a rigorous safety and efficacy assessment process before they are authorised for use. 


How were they developed so fast?

There are several reasons why these vaccines were developed so fast. The technology used is based on decades of research in different areas (virology, immunology, chemistry); pharmaceutical industry moved forward with several phases at the same time; regulatory bodies were quick to evaluate the processes; there was a large participation in terms of volunteers, which allowed robust analysis of the results.


Can the RNA of the virus alter our genetic code?

No. The nucleic acid fragment used in vaccines only serves to instruct our cells to produce the Spike protein, which will then be recognised by the cells of the immune system.


Why do we need to store vaccines at such low temperatures?

Because RNA is more stable at these temperatures, and this protects the vaccines from degradation.


Can children be vaccinated?

These vaccines have been tested in adults, because children do not usually develop severe disease, and they do not seem to contribute significantly to the transmission of the virus.


I had COVID-19. Should I be vaccinated?

There are studies (at least in the pre-print version) suggesting that for individuals who have already had SARS-CoV-2 infection, one dose of vaccine will be enough to raise antibody production to protective levels. This is because they will already have a certain immunity, which will be boosted by the vaccine dose. Taking antibodies as an example, in a previously infected individual there will already be memory, and one dose of vaccine will raise the level of these antibodies to levels similar to those seen after two doses of vaccine given to naïve individuals (who have never been infected with SARS-CoV-2).


What are the main side effects of the vaccines?

From studies and real-time monitoring of vaccination, there do not seem to be any major side effects. There are cases of fatigue, headache, pain or localised swelling. No studies report severe or prolonged side effects.


Why do we need two doses? The first dose prepares the immune system, gives the first instructions, and the second acts as a “boost”, an enhancer of the response. Thus, the protective response will be maximum after the second dose.


Why are they given 3 weeks apart?

This is the interval tested in studies carried out and considered optimal for the second dose to work. In principle there will be maximum antibody production after the 2 doses given 3 weeks apart. This is not to say that the vaccine does not work effectively if a different protocol is used.


Do the vaccines contain the virus?

The vaccines approved in Europe do not currently contain the virus. 


Will we only need to be vaccinated once? Or will it be necessary to repeat every year?

We don't know. We will have to wait for research in this area to be able to answer this question.


Why can variants of the virus escape the vaccine?

It is possible that a variant virus changes the conformation of the Spike protein and therefore its recognition by the antibodies produced in response to the vaccine. If this happens, the virus can escape the vaccine.


If I am vaccinated, will I stop transmitting the virus if I am infected?

Apparently not. The vaccine appears to protect against a severe manifestation of COVID-19. It is possible that vaccinated individuals are asymptomatic but can transmit the virus.


Why do we need to vaccinate 70% of the population?

This is the estimated figure to achieve herd immunity. Herd immunity is important because it limits the spread of infection by protecting individuals who cannot be vaccinated.



Coordination team:

Catarina Ramos, FC

Diana Mendes Freire, CV

Inês Domingues, iMM

João Filipe Marques, CV

Marta Moita, FC

Scientific curatorship:

Helena Soares, CEDOC

Luís Graça, iMM

Maria João Amorim, IGC

Thiago Carvalho, FC



Ana Mena, IGC

Inês Domingues, iMM

Catarina Ramos, FC

Marta Moita, FC



Helena Soares, CEDOC

Margarida Saraiva, i3S e SPI

Miguel Prudêncio, iMM

Training volunteers:

André Valente, FC

Daniel Nunes, FC

Helena Soares, CEDOC

Margarida Saraiva, i3S e SPI

Design and Web Design:

Ciência Viva


Video script and subtitles:

Anna Hobbiss, CEDOC e FC

Inês Domingues, iMM

Catarina Pimentel, FC

Catarina Ramos, FC

Marta Moita, FC


Video Production:

Ciência Viva


English translation:

Ciência Viva