The corona vaccine from the Mainz-based company Biontech and its US partner Pfizer is in use. It has been extensively tested and the data from the test series are promising. What is known about the substance – and what is not.

How does the vaccine work?

The product from Biontech and Pfizer is a so-called mRNA vaccine. No vaccine of this type has yet been approved for humans. The difference to conventional vaccines: It does not contain weakened or killed viruses, but only the instructions for a component of the Covid-19 pathogen, more precisely for a protein on the virus surface.


The assembly instructions consist of the mRNA molecule. The cells of the body produce the virus protein on this basis. The body then develops its immune response against this. In the event of later contact with the pathogen, the immune system recognizes the protein and can quickly fight the virus in a targeted manner. Because the vaccine only contains information for a single component of the virus, there is no risk of viruses spreading in the body after vaccination.

What has the vaccine proven to protect against?

“The vaccine trials show that people no longer get symptomatically ill,” says Andreas Podbielski, Director of the Institute for Medical Microbiology, Virology and Hygiene at the University of Rostock. It is currently unclear whether the vaccination will also prevent infection. “Of course we all hope that the vaccination will also prevent the infection, but we don’t know at the moment,” said Thomas Mertens, chairman of the Standing Vaccination Commission (Stiko) at the Robert Koch Institute recently of the “Frankfurter Allgemeine Sonntagszeitung” . It is conceivable that people who have been vaccinated may become infected and pass on the virus, although they themselves do not become ill.

How well does the vaccine protect?

According to the clinical studies, Biontech indicates the effectiveness of the vaccine with 95 percent. This means 95 percent fewer diseases occurred among the subjects in the vaccinated group than among the subjects in the control group.

It will only be seen in a few months whether the above-mentioned – for many experts surprisingly high – effectiveness is also achieved with massive use of the vaccine. The numbers refer to the phase 3 studies carried out so far, as virologist Podbielski explains. “The vaccination has now been carried out under idealized conditions,” he says. In everyday use, the conditions are not always ideal. The vaccine from Biontech has to be extremely cooled, says Podbielski as an example. He doubts whether a complete cold chain for vaccinations worldwide is possible.

Another problem that applies to all Covid vaccines: The tests are mainly carried out on healthy people. The immune system in older people or people with pre-existing conditions such as diabetes does not react as well to vaccinations as the immune system of healthy people. In this respect, according to Podbielski, it can happen that the data on the effectiveness of the vaccines are less good after vaccination of large parts of the world population. When presenting the first results of the phase 3 study, Biontech reported that it had not found any difference between different age groups in terms of effectiveness.

What influence do virus mutations have on effectiveness?

The genetic makeup of the coronavirus is constantly changing, which in itself is not unusual. The genetic changes can also change the properties of the virus, such as making it easier for it to infect human cells or to better escape attacks by the immune system. In Great Britain, for example, a new virus variant has been circulating for some time that is spreading much faster than the previous variants. Experts estimate the risk that the vaccine used in Great Britain against this variant will no longer work or work worse. The immune responses that the vaccine elicits are directed against several features of the virus, so individual mutations should not have dramatic effects.


How long does the vaccine protect?

This question cannot be answered conclusively either, because the studies have not yet run long enough. A recently published US study provides initial indications. According to this, both antibodies and T cells – two of the central weapons of our immune system – are still detectable in humans after a natural infection at least five months after the onset of symptoms. This is the case even with courses with mild symptoms. The study was published as a so-called preprint, so it has not yet been reviewed by independent experts.

Further studies show that with coronaviruses other than Sars-CoV-2, which causes normal colds, one is protected from renewed infection for one to one and a half years. When vaccinated, the immune response is generally more efficient, says Carsten Watzl, an immunologist at the Leibniz Institute for Labor Research at the Technical University of Dortmund. “So the hope is that the vaccine candidates will keep immunity much longer.”

What are the side effects of the Biontech and Pfizer vaccine?

Fatigue, headache, and pain at the injection site are some of the most common side effects of the vaccination. According to vaccination experts, such side effects are common. According to a study of 44,820 participants – about half of whom had received the Biontech vaccine – some also complained of fever, chills, diarrhea, or aches and pains in their muscles and limbs. In general, the side effects were mild to moderate and resolved after a short time. Compared to many established vaccines, such as the one against the flu, the side effects occurred comparatively more frequently. Vaccination experts compared the reactions with those given a shingles vaccine.

Occasionally there were “adverse events” such as swollen lymph nodes in the tests. One person each reported a shoulder injury, cardiac arrhythmia, and paresthesia in the leg, i.e. numbness. In principle, side effects occurred more often with the second vaccination dose. Possible rarely occurring side effects could not yet be recorded due to the short observation time. Therefore, the tolerance of the vaccine will continue to be tested after approval.


When vaccinated in the UK, some people had shown more severe allergic reactions. For this reason, the authorities have ordered people with severe allergy problems not to vaccinate for the time being. The fact that the problem did not arise in the clinical trials is simply because people with severe allergies to vaccines or components thereof were excluded from participation, Biontech CEO Sean Marett recently explained.

With a view to the vaccinations that are expected to begin in Germany as well, the German allergological societies emphasized in a statement that patients must be informed about the possible allergic reactions before vaccination. In addition, it must be asked whether a patient has had such problems before.

How is vaccination done?

Each patient receives two doses of vaccine at an interval of three weeks, each of which is injected into the upper arm – more precisely into the deltoid muscle (Musculus deltoideus). “In principle, it could be injected into any muscle, but the area on the arm is easily accessible,” says virologist Podbielski. The advantage of such an intramuscular vaccination: The active ingredient stays in the muscle for a few hours, giving the body time to recognize it and react to it.