To the Editor,

Dear Editor, we would like to comment on the article "Incidencia y factores asociados con las reacciones adversas tras la primera dosis de la vacuna Pfizer-BioNTech en trabajadores de la salud¹." In order to estimate the frequency of adverse reactions (AR) following the initial dosage of the Pfizer-BioNTech vaccine and to pinpoint some risk variables for AR, López-Contreras et al. According to López-Contreras et al. There is a 20% chance that a health care worker will get an AR as a result of the Pfizer-BioNTech vaccination¹.

The relationship that exists in reality might or might not be different from what is stated in the report. It is an interesting clinical problem when COVID-19 immunization has negative side effects. Articles may provide case-specific data, but it is impossible to establish with certainty how confounding factors affect results. It could be challenging to choose the right action to take. The objective of the current study, which aims to examine the effects of COVID-19 vaccine aversion, appears to be highly subjective. Determining the precise reason of a vaccination reaction may be challenging due to a paucity of clinical data defining the physiological and immunological status of COVID-19 vaccine recipients prior to vaccine injection. It is challenging to prove that there is no confounding factor given the registry's retrospective analysis.

Comorbidities are rarely mentioned in clinical records, even when they exist. Due to a lack of expertise, determining the precise patho-immuno-pharmacological link can be difficult at times. It can be difficult to understand how concurrent medical problems affect clinical outcomes. Genetics is the least important². More information is difficult to obtain when no new data can be used to support any of the existing study’s conclusions. At the end, it is possible to say that the proposed "no association" can be verified. However, another possible investigation that takes into account factors would be needed.