Carsten Watzl explains Covid 19 vaccines in the European Journal of Immunolgy

April 11, 2022

In a recent article, Carsten Watzl, Head of Department Immunology, points out the misconceptions about SARS-CoV-2 and vaccination that are widespread among the public and contrasts them with the scientific findings from an immunologist’s point of view.

The essential statements are summarised below:

COVID-19 vaccines affect fertility in younger women

COVID-19 vaccines have no effect on female or male fertility (whereas SARS-CoV-2 infection can negatively affect sperm quality in men). They are as safe and effective in pregnant women as they are in non-pregnant women. Vaccination during pregnancy can protect babies for the first months after birth from hospitalization with COVID-19, and during nursing protective antibodies but not the vaccine can be transmitted to the baby.

Natural immunity is better than vaccination

Therefore, immunity by infection comes with a greater risk than immunity by vaccination. But is the immunity after an infection better? The decay of neutralizing antibody levels is slower in individuals after a SARS-CoV-2 infection compared to vaccination. And the immune system responds to all antigens of the virus during an infection, whereas only spike-specific responses are induced by most vaccines. Therefore, immunity after infection can have its benefits. But it is not sufficient. After an infection with variants prior to omicron, individuals have very few if any antibodies that can neutralize the omicron variant. Vice versa, an infection with omicron does not provide good protection against other variants of the virus. The best form of immunity currently known is ‘hybrid immunity’, a result of vaccination AND infection.

If vaccines work, why was I infected after vaccination?

During an infection, B cells and T cells that can recognize the pathogen start to proliferate and to build up a large army that will fight the invader. After the infection is cleared and the antigen is gone, many of these cells will die, as it would be non-economical for the immune system to keep all these cells around. Only a few cells survive in form of memory cells. As already mentioned, vaccines induce a similar immune response as an infection does. Also, after vaccination, many of the antibody-producing cells will die. Therefore, antibody titers typically drop quite fast within the first months after vaccination. However, they stabilize to a long-lasting antibody titer that is maintained by antibody producing memory cells. While such a long-lasting titer may be sufficient to protect against an infection with measles for many decades, you need quite high antibody titers to be protected from a respiratory infection such as with SARS-CoV-2. As omicron carries so many mutations in its spike protein, many of the vaccine-induced antibodies cannot recognize this variant, which is the main reason why protection from infection, especially with omicron, is not optimal and is waning with time. However, the vaccines still protect from severe disease if you do get a breakthrough infection, as this protection is mediated by long-lived memory cells. Therefore, vaccines do work, also against omicron, as they protect against severe disease!

Photo: PIRO4D/

Coronavirus is just another respiratory virus similar to influenza virus

Similar to influenza, age is a major risk factor for a SARS-CoV-2 infection. However, the big difference between these two viruses is that almost no one had any pre-existing immunity against SARS-CoV-2, which resulted in a much higher case-fatality rate in the first year of the pandemic. While the current omicron variant has lower intrinsic pathogenicity compared to previous variants, future variants may again be as pathogenic as the delta variant. Therefore, it is not the virus that necessarily changes to become less dangerous. We must change. And we are slowly changing, mostly by vaccination-induced immunity. Through this change we may reach a state in the future, where SARS-CoV-2 is indeed only as dangerous as the flu. But when people make this comparison, they often try to argue that vaccinations or other non-pharmaceutical interventions such as social distancing and masks are not necessary. And without vaccinations, SARS-CoV-2 would remain much more dangerous than the influenza virus for many years to come.

All currently approved vaccines were developed fast, so their safety is questioned

The development of COVID-19 vaccines did not start with the emergence of SARS-CoV-2. And the testing of these vaccine candidates was much faster. Not because critical safety steps were omitted. Regulatory authorities sped up their approval and review process and the pharmaceutical companies were able to recruit phase 3 trials of up to 40.000 participants within weeks because many people were interested in participating in these trials. Typically, recruiting so many participants in a vaccine trail can sometimes take years. And finally, the number of infections needed to determine the efficacy of the vaccines was quickly reached, as the trials took place in countries and at a time with high SARS-CoV-2 infection rates.

And these studies were very large compared to other vaccine trials, thereby enabling the detection of more uncommon events. But as side effects are often very rare, they are mostly detected upon vaccinating millions of people after approval of the vaccine. Therefore, it is a strength of the COVID-19 vaccines, that they were administered to many people within a short time frame. This made it possible to quickly detect very rare side effects that only affect less than one in 100.000 vaccinated individuals. In essence, we know more about the safety of the COVID-19 vaccines than about many other vaccines within the same time frame.

Original publication:

Watzl, C. (2022), COVID-19 vaccines – common misperceptions, false claims and myths explained. Eur. J. Immunol.

Scientific Contact: 
Prof. Dr. Carsten Watzl
Head of Department Immunology
Phone: +49 231 1084-233

Press Contact:
Anne Rommel
Press Officer
Phone: +49 231 1084-239