Are the COVID-19 vaccines safe?

by Bram

By far, most experts around the world agree and say:

“Take any approved COVID-19 vaccine that is offered to you, and take it as soon as possible.”

  • How can the COVID-19 vaccines be developed so quickly?
  • Have any corners been cut?
  • Why don’t we need to worry about long-term side effects?
  • Is it safe?

Particularly for people with MS, an additional question is:

  • Why do experts say that it won’t harm people with MS?

For our Dutch non-profit organization ‘MS in beeld’, I created a web page as well as a number of videos that discuss these topics in detail. Unfortunately, all this information is in Dutch. As people worldwide are asking these same questions, I decided to translate our webpage into English. I believe that this can help you understand the vaccines’ safety.

How can the COVID-19 vaccines be developed so quickly?

It usually takes much longer to develop a vaccine. Today, more than 600 million vaccinations have been given against COVID-19 within a single year. It almost seems inevitable that corners had to be cut.

Still, there are logical explanations for the rapid development, production, and distribution of vaccines.

Reason 1: Science has advanced

Usually, a research institute researches a vaccine, e.g., a university or a pharmaceutical company’s research lab. All these research groups have learned a great deal in recent decades. Most labs already had a platform ready to develop a vaccine for the novel coronavirus.
Some labs were already making vaccines against SARS-CoV and MERS-CoV. Adapting the process to SARS-CoV2 (the name of the virus causing COVID-19) was relatively straightforward.

That is why some labs could start making prototypes almost immediately after Chinese researchers published the genetic code of the virus.

Reason 2: Waste is accepted by parallelizing activities

A huge amount of money has been invested by governments, organizations, companies, privately, etc. The will to invest is there because currently, this pandemic costs the world about 500 billion dollars every month. All the money was not used to bribe regulatory agents but to accelerate every step of development, approval, manufacturing, and distribution.

Typically, experiments are conducted sequentially, after each other; now, they are run in parallel, side by side. at the same time. Many of the experiments lead to nothing, but some do. Working this way causes waste, but it leads to results much more quickly.

Reason 3: The regulatory agencies started reviewing immediately

Typically, the regulatory agencies like the FDA or EMA do not review vaccines or drugs until the phase I, II, and III studies have all been completed. Now they already started their reviews during the studies. They call this a ‘rolling review.’ This not only sped up the review process itself, but researchers were informed early if data were missing, or additional data was required.

Reason 4: Mass manufacturing of the vaccine started early

After a safe and effective vaccine has been approved by the authorities, it still takes a long time to produce many shots.

With a typical vaccine, they only start manufacturing after a vaccine is approved. In this case, a lot of money is invested in starting manufacturing the vaccines before their approval, even before the completion of the Phase III trials. There is a risk that large quantities of unsuccessful vaccines have to be destroyed. The benefit is that once a vaccine gets approved, factories are up and ready, or perhaps have even started production.

Reason 5: Logistics and strategies were thought out in advance

Most countries already prepared the distribution process and vaccination strategy deciding who to prioritize for vaccination.

Have any corners been cut?

All medicines and vaccines are first tested in pre-clinical studies, i.e., studies with laboratory animals, followed by clinical studies. These research studies on humans are divided into several phases (Phase I, II, and III prior to approval, and IV post-marketing surveillance). The same holds for the COVID-19 vaccines. The regulatory agencies are not allowed to cut corners.

The video below by the BBC explains how a vaccine gets approved.

Why don’t we have to worry about long-term side effects?

A vaccine is different from a medicine that you take continuously. The mRNA or DNA that is injected when a vaccine is given disintegrates within a few days. All that remains is an immune system that has been trained in recognizing the novel coronavirus. The generated immune response to a vaccine is well controlled, unlike a viral infection that often floods the body with millions of viral particles.

After having thoroughly reviewed studies with vaccines in the past, experts concluded that all side-effects exhibit themselves in less than six weeks, including the rare ones. Therefore, the authorities have decided that it is sufficient for the clinical studies to follow subjects for six weeks. It is believed that possible side effects, even the long-term side effects, would have manifested within that time period.

This does not mean that vaccines cannot possibly cause any long-term problems, it means that these would have already been noticeable within six weeks after the vaccine was administered.

Although the vaccines are tested on tens of thousands of subjects in their Phase III trials, very rare side effects may not have occurred in the study population due to their very low likelihood and can therefore not be ruled out. This is why possible side effects of the vaccine are also closely monitored after approval.

Is it safe?

More than 600 million vaccinations against COVID-19 have already been given worldwide, and fortunately, the number of reported side effects is very low.
These reported possible side effects are dwarfed by the risks that a COVID-19 infection itself entails. That is very important: vaccination is in no way worse than the actual disease.

I imagine it like this, suppose that you gave 600 million people a free sample of peanuts, then the number of reported side effects would have been far greater than the number of side effects that have been reported for the COVID-19 vaccines so far.

Why do experts agree that COVID-19 vaccines won’t harm people with MS?

The vaccines have not been tested explicitly in people with MS. In Phase II and III clinical studies, the vaccine was tested on many people, including dozens of people with MS.
Even though the pharmacists have not given specific results for people with MS, we know there were no strange side-effects that happened to people with MS in those studies.

Experts also know from past studies 12 that there does not appear to be a link between vaccinations and MS relapses.

Without a doubt, the hundreds of millions of people that have received their COVID-19 vaccine included tens of thousands of people with MS. So far, no evidence has been found that the vaccines can cause neurological problems or lead to MS relapses.

This is not to say that these side effects have not been reported, but that the amount of reported neurological side effects is no different from what you would normally measure in the population without vaccination.

What can happen is a so-called pseudo-relapse: after vaccination, your MS symptoms could temporarily worsen. That’s because your body is busy making an immune response to the vaccine, which might cause a fever. That is normal. Fever can lead to a temporary increase of pre-existing symptoms. Fortunately, it does not trigger a relapse. This worsening of neurological symptoms when the body gets overheated is also referred to as Uhthoff’s phenomenon. Fortunately, it will resolve as soon as the fever resides. A pseudo-relapse does not leave any lasting damage. (Some people with MS also notice the same on a scorching summer’s day.)

Taking Tylenol (paracetamol) after vaccination can reduce discomfort and has no detrimental effect on the vaccination.

In MS, it is crucial to keep in mind that infection with COVID-19 itself can lead to much worse outcomes. Your immune system can overreact because your body is overrun with viruses that divide at lightning speed. Such an overreaction can, in rare cases, be deadly, but in MS, even a mild infection with COVID-19 might trigger a relapse.


Although at the moment a lot is not yet 100% certain, we can say with utmost certainty:

The likelihood of developing a COVID-19 infection that causes health issues
is far greater than
the health risks of an approved COVID-19 vaccine

And that’s the most important thing to know. Therefore, the advice of almost all experts is:

“Take any approved COVID-19 vaccine that is offered to you, and take it as soon as possible.”

  1. Mailand, M. T. & Frederiksen, J. L. Vaccines and multiple sclerosis: a systematic review. Journal of Neurology 264, 1035–1050 (2017)
  2. Zrzavy, T. et al. Vaccination in Multiple Sclerosis: Friend or Foe? Frontiers in Immunology 10, (2019)

This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More