gms | German Medical Science

Background: Hospital personnel, in addition to the elderly, were the first group immediately vaccinated after approval of the first Covid-19 vaccines. Up to this point, only data from pivotal efficacy trials were available. All effects of the new Covid-19 vaccines were evaluated in placebo-controlled clinical studies. Placebo effects are beneficial effects that do not arise from the treatment itself. Paradoxical placebo effects are negative effects that occur in persons with positive expectations towards a medical procedure. Adverse events that occur in the placebo group are called nocebo effects. Valid statements on the tolerability of new drugs and procedures are best collected in unselected samples after approval. There are placebo and nocebo effects in every vaccination as all available information influences the vaccinated persons in a positive or negative sense. Not only because of the novelty of the vaccines and the harmfulness of the coronavirus, there might have been numerous fears associated with its use as well as many hopes, especially in hospital staff that has seen many patients dying of or with Covid-19 for months. Traditionally, there are many vaccination sceptics in Germany. Vice versa, it has been described that the German population showed only a moderate level of Covid-19-vaccine acceptance. The main goal of our study is to determine possible nocebo and placebo effects of the Covid-19 vaccinations in a hospital staff population.

Materials and Methods: Each employee of Klinikum Nuremberg (a large community based hospital) was offered the opportunity to participate in our study on a voluntary basis and to provide anonymized information on personal and health data, e.g., body measurements, health status, previous illnesses and vaccination side effects within one week after the first and second COVID-19 vaccinations. We used standardized questionnaires to record local and systemic side effects and defined risk groups regarding possible nocebo effects. Negative experiences with former vaccinations and/or fears about the course of the vaccination and/or the feeling of not being informed about the vaccination were defined as risk factors. Moreover, the time of vaccination could have an influence, too. Intensive care units workers were prioritized for vaccination. Hospital personnel that has been confronted with many negative disease progressions might show higher psychological strain and greater expectations with regard to the vaccinations than “normal” hospital staff. Hence, we will compare hospital staff that was vaccinated with mRNA vaccine BNT162b2 during December 2020 and January 21 with employees vaccinated at a later time point (vaccination interval of 3 weeks). Secondly, we will also evaluate the adverse events of the ChAdOx1 vaccination (AstraZeneca) in hospital staff that was vaccinated early (i.e., February 21) and compare them with employees vaccinated at a later time point (vaccination interval of 6 weeks, homologous or heterologous vaccination with mRNA vaccine). We will use propensity score matching for the statistical analysis, i.e. we will allocate to each employee vaccinated early an employee vaccinated late (matched pairs age and gender). The study was approved by the local institution review board.

Results: 2146 participants took part in our study, the male : female ratio was about 1: 3.5. Pre-existing conditions were use of contraceptives, pacemakers, implants, radiation therapy, physical therapy, diet, allergies, metabolic diseases, other diseases, vaccination complications, COVID infection. 10% of the sample answered that they had concerns about the course of the vaccination, 32% did not. 4.1% had negative experiences with former vaccinations, 28.8% answered that they felt well informed about the vaccination. Further analyses will show if we can find possible placebo and nocebo effects.

Conclusion: The determination of predictors for placebo and nocebo effects in vaccinations could be useful for clinical studies