Different types of COVID-19 vaccine work in different ways, but safety always comes first. The vaccines must meet strict conditions.
How coronavirus vaccines work
The Pfizer and Moderna vaccines are mRNA vaccines. They contain messenger RNA that instructs the cells in our body to make a harmless protein called a spike protein, which triggers a response by our immune system. After vaccination, when our cells have finished making the spike protein, they break down all the mRNA molecules and remove them. The spike protein is also found on the surface of the virus that causes COVID-19. When our body is exposed to coronavirus, our immune system recognises the spike proteins on its surface and makes antibodies to get rid of the virus.
The AstraZeneca and Janssen vaccines are viral vector vaccines. They contain a harmless cold virus that gives a ‘code’ to our cells so that they make a harmless protein called a spike protein. This triggers our immune system, which makes antibodies against the spike protein. If our body is exposed to coronavirus after vaccination, our immune system can respond quickly to get rid of the virus.
The Novavax protein subunit vaccine contains a version of the SARS-CoV-2 virus’ spike protein that has been produced in a laboratory. It also contains an ‘adjuvant’, a substance that helps strengthen the body’s immune response to the vaccine. When a person is given the vaccine, their immune system will produce antibodies.
If, later on, the vaccinated person comes into contact with SARS-CoV-2, their immune system will recognise the spike protein on the virus and stop the virus entering the cells in their body and replicating itself. This means the risk of illness and serious illness is smaller.
If you have been fully vaccinated against coronavirus, you are less likely to be admitted to hospital with COVID-19 than an unvaccinated person. You are also less likely to be admitted to an intensive care unit (ICU) with COVID- 19.
You can still get COVID-19 after being fully vaccinated, but you will be less infectious than an unvaccinated person. There will still be infectious virus particles in your body, but the overall viral load is much lower.
The safety of coronavirus vaccines comes first. Like all vaccines, they must meet strict conditions before they are authorised for use in the Netherlands. If there are any doubts about their safety, they will not be approved. There are also strict rules on side effects. The advantages of vaccination (effectiveness) must be greater than the disadvantages (possible side effects).
A new vaccine is first assessed by the European Medicines Agency (EMA). For authorisation in the Netherlands, it is then assessed by the Medicines Evaluation Board (CBG). Both organisations examine and assess the vaccine’s safety, reliability and efficacy. They continue monitoring the vaccines after they have been authorised. A European surveillance system is being set up to monitor vaccine safety.
COVID-19 vaccines have been developed quickly by a range of manufacturers. There are several reasons why they have been able to do this:
All over the world, various manufacturers have been working to produce different COVID-19 vaccines and to share knowledge.
Researchers have been working on different stages of development simultaneously, rather than consecutively, to save time.
Independent regulatory authorities have been deploying additional staff and assessing interim research results.
You may have questions about getting vaccinated in certain situations. For example if you:
take certain medication;
have an allergy;
are seriously ill;
have coronavirus or get infected between the first and second doses; or
have a weakened immune system (immunocompromised).
The vaccines also work for people with a weakened immune system, but the level of protection varies. It is important for these people to get both doses of vaccine, because they have a higher risk of getting seriously ill if they contract COVID-19.
If you had an allergic reaction to a vaccine before, you can usually still be fully vaccinated against coronavirus. If you are allergic or think you might be, speak to your family doctor. If necessary, they can refer you to an allergist, a doctor who specialises in diagnosing, treating and managing allergies. An allergist will be able to tell you what the best course of action is in your situation.
Pregnancy and the COVID-19 vaccine
The National Institute for Public Health and the Environment (RIVM) advises all pregnant women to get vaccinated with an mRNA vaccine (BioNTech/Pfizer or Moderna). This also applies to the repeat vaccination with the renewed mRNA COVID-19 vaccines.
You can safely get vaccinated against COVID‑19 at any time during your pregnancy. There is no indication that getting vaccinated during the first trimester can lead to complications. This also applies to the booster vaccination. If you prefer you can wait until after the first trimester to get vaccinated. However, you are advised not to wait until the end of your pregnancy; people who get COVID‑19 in late pregnancy are at greater risk of experiencing complications.
You do not need to plan any time between a COVID-19 vaccination and other vaccinations. You could even get both on the same day.
There is currently no indication that getting vaccinated against COVID‑19 may be harmful to you or your unborn child. Newborn babies are protected against infectious diseases by the antibodies they get from their mother through the placenta. This also appears to be the case with the COVID‑19 vaccine.
The vaccine does not affect the fertility of either women or men. Nor does it have an impact on the development of the placenta. This is according to toxicity studies carried out by the vaccine manufacturers. Furthermore, according to the Netherlands Society of Obstetrics and Gynaecology (NVOG) and RIVM, vaccination against COVID‑19 is possible when undergoing in vitro fertilisation (IVF) treatment.
You can breastfeed if you’ve been vaccinated. According to RIVM, there is no indication that the vaccine enters a woman’s breast milk or that it can be passed on to a child through breastfeeding.
Side effects
The coronavirus vaccines have been tested on tens of thousands of people. Some people have muscle ache or a fever for a few days after being vaccinated. This is common with vaccines against other diseases, too. Side effects usually occur within 2 weeks.
It’s possible that unknown side effects might occur after vaccination against COVID-19. But the chance of this is very small. If you experience unknown side effects or you are worried, contact your family doctor.
Lareb is the organisation in the Netherlands that gathers, registers and investigates possible side effects. If you experience side effects, you can report them on Mijnbijwerking.nl. The Medicines Evaluation Board (CBG) assesses whether a vaccine is effective and safe. If necessary it takes measures to protect public health.
There have been reports of people developing myocarditis or pericarditis after COVID-19 vaccination. Myocarditis is inflammation of the heart muscle. Pericarditis is inflammation of the heart sac. The EMA is investigating these reports.
A registration system records which vaccine you have been given. For most vaccines, people require two doses of the same vaccine for optimal protection against COVID‑19. Registration is important, not just to invite people to get their second dose, but also to know how many people have already been vaccinated and whether the vaccine is safe and effective. Registration is voluntary and the register is subject to privacy regulations (in Dutch).
