What happens in your body after a vaccination?

In Switzerland, people who do not belong to the risk groups can now also be vaccinated against the corona virus. What happens in your body after a vaccination? Some explanations.

What happens in your body after a vaccination?
Human beings are exposed to many pathogens in their everyday lives. These can be, for example, viruses, bacteria, fungi and parasites. The immune system defends you against these pathogens - it is the defence system of our body.

But the immune system sometimes cannot provide sufficient defence. This may be the case when a new pathogen enters the body for the first time. As a result, you become ill.

A vaccination imitates the attack of a pathogen on your body, and gives your body the opportunity to practice its defence against the pathogen. In order to do this, weaker forms or parts of the pathogen are introduced to your body, usually via injection.

The vaccination against the corona virus is a little more complicated: in this case, the pathogen itself is not administered, but, instead, a building instruction for a part of the pathogen. More about this can be seen in the section on mRNA vaccinations.

No matter what kind of vaccination is carried out: the immune system creates antibodies in response. These antibodies then fight against the pathogens and any other foreign substances. The immune system thereby remembers which defence was most effective, and future infections with the same pathogen can then be fought more effectively and quickly.

Through a vaccination, your body practices its defence system. If the real pathogen tries to enter your body at a later date, your body can fight against it better.

This is how Swissmedic explains the process of vaccination in a video. (Swissmedic is the regulatory and supervisory authority for medicinal products and medical devices in Switzerland).

How is a vaccine developed?
In the beginning there is a pathogen: in the current case, that's the corona virus. If you want to fight it, you first have to understand it. So scientists start by analysing the virus.

They then develop the vaccine: the scientists investigate which substances this should include, and determine what properties the vaccine should have.

The scientists then bring together the initial findings of tests on cell cultures and animals. If the results are good, the vaccine can be tested on humans.

Once the vaccine has passed this test, the pharmaceutical company submits an application to Swissmedic for distribution authorisation.

How was it possible to develop vaccines against the new coronavirus so quickly?
On its website, Infovac states that the development of a vaccine usually takes 10 to 20 years. Infovac is an online platform on which experts collect and publish information on the subject of vaccinations.

The vaccine against the coronavirus was developed much faster, however. According to the  Federal Office for Public Health (FOPH/BAG), there are various reasons for this:

• Scientists were able to gain time because they were able to carry out different phases of the development at the same time.

• Scientists also worked together across national borders. This is not always the case.

• Scientists researched the properties of the new corona virus and quickly made their results available to all.
• Pharmaceutical companies usually work on many different projects simultaneously, and need money and employees in order to do this. Many of these projects have now been interrupted, because it was important to quickly find a vaccine against Corona. As a reason, more money could be used for the development of the vaccine and more employees were able to participate.
• Major, experienced manufacturers were able to carry out efficient studies in a short time.
• Scientists have carried out a lot of research into vaccine technologies in recent years, and have been able to learn from these experiences. As a result, they can nowadays develop vaccines more quickly with the same technology.

How is a vaccine approved?
Before a vaccine can be distributed in Switzerland, it needs approval. Swissmedic is the Swiss body that decides whether a vaccine is approved.

To this end, Swissmedic examines three factors:

• the effectiveness
• the safety
• the quality

A pharmaceutical company will normally submit many different studies for this purpose. Only when all these studies have been completed will Swissmedic examine all the results together.

In the case of corona virus vaccinations, Swissmedic accelerated the procedure: as soon as a pharmaceutical company is able to present new findings from a study, it sends the results to Swissmedic, which then immediately reviews the results.

This procedure is called the "rolling process". The requirements for this rolling procedure remain the same as for the normal procedure.

Vaccinations against Corona are mRNA vaccinations. What does that mean?
The pharmaceutical companies Biontech/Pfizer and Moderna rely on mRNA technology for their vaccines. mRNA stands for Messenger ribonucleic acid.

mRNA is a kind of messenger molecule, which carries a building instruction with it. In the case of vaccination against corona, it carries the instructions for building a small part of the corona virus.

The coronavirus is a small sphere with spikes. The mRNA vaccination brings the instructions for building these spikes into the body. And only for these spikes, not for the whole virus. With these instructions, the body then builds the spikes of the corona virus.

The immune system now comes into play again. It detects the spikes, and forms antibodies against them. If the actual virus wants to penetrate your body at a later date, your body now already knows how to fight against the spikes. As a result, the virus cannot spread in your body.

Start of vaccination against the coronavirus: The first people receive a dose of the vaccine from Pfizer-BioNTech.
Photo: Sandra Ardizzone / AGR

Can an mRNA vaccine alter your DNA?
The answer from the FOPH is: No.
The mRNA that is administered with the vaccination cannot enter the cell nucleus, and thereby cannot become incorporated into the human DNA.

What side effects can a Covid-19 vaccine have?
Pfizer/BioNTech tested the vaccine in a study with 43,000 participants. Half of the people tested received the vaccine, while the other half received a substance without effect (a placebo).

In addition to mild reactions around the site of the injection, the following side effects were reported following the vaccinations:

• 62.9 % were tired after vaccination.
• 55.1 % complained of headaches.
• 31.9 % reported chills.
• 38.3 % reported aching muscles.
• 14.2 % had a fever.

These symptoms were all short-lived (1-2 days).

Four of the approximately 43,000 study participants suffered more severe side effects, such as temporary leg paralysis and a cardiac arrhythmia. These side effects were just as common in the vaccine group as in the group that did not receive a vaccine. This suggests that the side effects were not caused by the vaccination.

The side effects are similar with the Moderna vaccine. Moderna tested the vaccine in a  study on 30,000 people. Half of them received the vaccine, the other half did not receive a vaccine, so that they could be compared with the others. In addition to mild reactions around the injection site, the following side effects were reported:

• fatigue
• headache
• aching muscles
• joint pain
• shivering fits

0.6 % the group that received the vaccine suffered serious side effects (for example, heart attack, gallbladder inflammation and kidney stones). Exactly the same number of people reported these side effects in the group that did not receive the vaccine. There was therefore no evidence in the study that the serious side effects were triggered by the Covid-19 vaccination.

Younger immune systems react more strongly
The above side effects are more frequent in younger adults under the age of 60, according to Masha Maria Foursova, who is the spokesperson for the Federal Office of Public Health. The reason for this is that the immune system of younger people reacts more strongly than that of older people.

How long does vaccination protect against coronavirus?
This has not yet been fully clarified, and studies are ongoing. The Federal Office of Public Health increased the protective effect to 12 months in mid-June. It therefore expects the vaccination to be effective for at least 12 months.