There is no doubt that the majority of the population believes in the effectiveness and benefits of vaccination, and thus agrees with the scientific community. However, majority does not mean totality: in the United States, up to 9% of the population believes that vaccination is not effective or even dangerous 1, 2. Even more worryingly, it would seem that the number of “anti-vaxxers” is increasing over the years, leading the World Health Organization to consider vaccine hesitancy as one of the 10 threats to global health 3, 4. Vaccination has already proved its worth by eradicating smallpox, lymphatic filariasis or poliomyelitis in most countries 5. In view of the increase in the number of “anti-vaxxers”, the copious amount of misinformation circulating on the Internet 6, 7, 8 and the importance of vaccination (especially in times of global health crisis due to COVID-19), we have decided to tackle this subject.
How does it actually work?
How do vaccines protect us from pathogens (organisms that can cause a disease)? To be able to fully understand how vaccines work, we need to take a look at how the immune system works. When a virus or bacterium enters our body, our immune system has two tools at its disposal: the innate immune system and the adaptive immune system 9.
The innate immune system (or innate response) attacks the intruder (the virus or bacterium) in a general but rapid manner. This response can quickly get rid of the invader, but also can cause well-known sickness symptoms like coughing, sneezing, inflammation and fever. It is indeed our body that is responsible for all these symptoms, and not the pathogen! Unfortunately, sometimes the pathogen is stronger than this response and this is why we have a second kind of immunity: the adaptive immune system 9.
When the adaptive immune system is active, special cells known as lymphocytes will be produced by the body to fight the pathogen in a more effective and targeted way than the innate response. Lymphocytes can be one of two main kinds: B-cells and T-cells. B-cells can produce antibodies to recognise the pathogen and T-cells can destroy it. Furthermore, the body also has a special category of lymphocytes: memory cells. These cells are capable of identifying the infectious particle of the pathogen (or antigen) and remember it, so that if the body ever meets that pathogen again the immune response will be even quicker. Sadly, depending on who’s being attacked, this adaptive response can be too slow, for example, if the person is elderly or has a weak immune system 10.
So, what is a vaccine?
Imagine being able to tell the body to create these memory cells before even being infected. That is exactly what vaccines do by activating our adaptive immune system in advance. In fact, vaccines usually contain either the inactivated pathogen (so it can’t cause any disease) or just specific proteins from the pathogen (these antigens mentioned earlier) that the body will be able to learn to recognise. Once recognised, the body can create these memory cells and if the real pathogen ever arrives, it will be quickly eliminated, sometimes without any symptoms at all!
No matter the form of the vaccine, they all have the same goal: to activate the adaptive immune response without harming the person being vaccinated. Today, research into new, even more effective vaccines is ongoing and could even help defend against diseases such as Zika or AIDS 11,12,13.
Can a vaccine have side effects?
This is a legitimate question and concern that many people have. It’s true that the idea of protecting ourselves from a pathogen by injecting ourselves with it can be a little … confusing.
Most people do not experience any side effects from any vaccine. Vaccines go through a long series of tests and have to follow a very strict control protocol before being made available to the general population, which minimizes the risk of side effects 14 . Some vaccines do however come with some side effects such as a low fever, headache or muscle aches, but these are all due to the innate immune response that we discussed earlier 15.
What about more serious side effects? These are extremely rare and are due to an allergic reaction to the vaccine. Out of a million people vaccinated, only one or two of them will experience anything stronger than the mild side effects mentioned before 16. Keep in mind that vaccines are safe because they have gone through many tests before they even reach you, and are also effective helping eradicate diseases worldwide.
Why are vaccines important?
As we have seen, vaccines can protect us against many diseases. Vaccination is one of the central pillars of public health and stopping this practice would cause the return of diseases that most of us have been lucky to never experience, like polio for example. This has already happened once in recorded history: in 1970, when Japan experienced a return of whooping cough, a highly infectious bacterial disease that is particularly severe in new-borns. An anti-vaccination movement put pressure on the government, which in turn decided to stop vaccinations for whooping cough between 1974 and 1975. This led to an epidemic in 1979 with over 13’000 cases and 41 deaths 17,18.
Nowadays, the scientific community is constantly reminding us of the importance of vaccination to curb or even eradicate certain diseases. As mentioned in Nature and Heidi.news, amongst others, disinformation and misinformation on vaccines are ever more present in our society, sometimes even spread by those with strong influences 19,20. It is the duty of scientists to respond to this wave of fear when it comes to vaccines, but it is also the duty of society to be critical of the information it receives, as vaccines remain one of our best defences against future epidemics.
For more information, check out these resources:
- A great video about how the immune system works : https://www.youtube.com/watch?v=PSRJfaAYkW4
- More informations about vaccines and a little quiz at the end : http://www.historyofvaccines.org/content/how-vaccines-work
- You can read more about all the different types of vaccines here : https://www.publichealth.org/public-awareness/understanding-vaccines/vaccines-work/
References:
- https://www.washingtonpost.com/news/the-fix/wp/2015/02/09/heres-how-many-americans-are-actually-anti-vaxxers/
- https://ourworldindata.org/vaccination#public-support-and-skepticism
- https://www.who.int/news-room/feature-stories/ten-threats-to-global-health-in-2019
- https://www.ft.com/content/38923eb0-92a0-11e9-8ff4-699df1c62544
- https://www.historyofvaccines.org/content/articles/disease-eradication
- https://pubmed.ncbi.nlm.nih.gov/29553872/?from_term=vaccination+misinformation&from_pos=1
- https://pubmed.ncbi.nlm.nih.gov/31640660/?from_term=vaccination+misinformation+internet+&from_pos=2
- https://www.nature.com/articles/d41586-018-07034-4
- https://www.ncbi.nlm.nih.gov/books/NBK27090/
- https://ed.ted.com/lessons/how-do-vaccines-work-kelwalin-dhanasarnsombut#revie
- https://www.technologyreview.com/2016/08/02/158531/us-government-starts-test-of-zika-vaccine-in-humans/
- https://www.pnas.org/content/90/9/4156.long
- https://www.sciencedirect.com/science/article/pii/S004268228571238X?via%3Dihub
- https://www.cdc.gov/vaccines/basics/test-approve.html
- https://www.cdc.gov/vaccines/vac-gen/side-effects.htm
- vaccines.gov/basics/safety(opens in a new tab)
- https://www.tandfonline.com/doi/full/10.1586/14760584.4.2.173
- https://familydoctor.org/the-importance-of-vaccinations/
- https://www.nature.com/articles/d41586-020-01550-y?utm_source=twt_nnc&utm_medium=social&utm_campaign=naturenews
- https://www.heidi.news/sciences/l-hypocrisie-opportuniste-des-antivaccins-apres-la-crise-du-coronavirus
