When the Vaccination Becomes a Boomerang

Surprise is the name of the study. And a surprise is also the explosive result: the study, published in 2025 in «Nature Communications», shows that the frequency of so-called influenza-like illness (flu-like cold, abbreviated ILI) was higher after the COVID-19 vaccination – especially in the frist few weeks after the third and fourth dose.

What dose “influenza-like illness” mean?

ILI is a medical collective term for diseases that are similar to flu but are not necessarily caused by influenza viruses. Typically, the definition includes fever in combination with cough, sore throat, body pain or a general feeling of illness. In the st. Gallen cohort, these symptoms where recorded every week by online questionnaire, supplemented by tests when it was medically indicated.

The most important results

The analysis included the flu season from November 2023 to April 2024. Especially after the third and fourth COVID-19 vaccination, the ILI new diseases were considerably increased in the first few weeks. The following figure shows that a large proportion of flu fell ill with the never vaccinated (far left), and that the more often the person was vaccinated.

[Image: The more vaccination boxes (scale below), the higher the disease rate on ILI (scale on the left; pink: no ILI, yellow: an ILI, green: several ILI).]

In the first two vaccinations, the difference was not yet meaningful – though, these vaccinations for most participants were more than two and a half years ago. Since the negative effect decreased significantly over time, it is not excluded that the early vaccinations could have triggered increased susceptibility to infection at the time, but this is later no longer recognizable statistically.

A well-known pattern

The observation that more ILI occurs after a vaccination is not an individual finding, but is part of a whole series of similar results. Several major studies report that the risk of respiratory infections – including COVID-19 – can be increased in the weeks after an mRNA vaccination, with a clear dose-effect relationship. For the interested reader, I have described some of these studies in more detail below. this work supports my statement made almost three years ago: Stop the booster!

the Danish research team led by Christine Benn analyzes that non-specific side effects are also possible after vaccination.A meta-analysis of this group (Preliminary print) shows that the COVID-19 vaccination in children under the age of 18 increases the risk of respiratory infections (including RSV) by almost triple.

A plausible mechanism

It is indeed biologically plausible that such effects arise. Several independent teams, including the research group…

The Unexpected Impact of mRNA Covid Vaccines on Infection Risk

The debate around Covid-19 vaccination is complex. Recent research from the St.Gallen cohort adds a crucial viewpoint: we must consider how vaccines affect overall susceptibility to all infections, not just the target virus. Focusing solely on protection against covid-19 could mask unintended consequences. Science demands we investigate even uncomfortable findings.