Effectiveness of Covid-19 Pfizer/BioNTech vaccine through incidence and survival analysis in Mexican health care workers

Abstract

Background: The Covid-19 pandemic promoted the need to evaluate vaccines effectiveness in different groups from those used in the clinical research phases.

Objective: To analyze the effectiveness of the basic scheme with the Pfizer-BioNTech vaccine through the incidence of Covid-19 and survival analysis, in health workers assigned to a second-level hospital in the State of Chiapas, Mexico.

Material and Methods: We used an instrument with variables of the following types: sociodemographic, comorbidities, vaccination with Pfizer-BioNTech, disease and Covid-19 diagnosis. The Odds Ratio was calculated to study the relationship of Covid-19 diagnosis with the variables under study, followed by a survival analysis (Kaplan-Meier) and survival curves (Log-Rank).

Results: Of an inferential sample of 254 individuals, 55.5% were women, with a mean age of 38.8 years; 22.4% were classified as normal-weight; and 18.5% had some comorbidity; 32.3% reported they got ill after taking the complete vaccine schedule. The probability of not getting sick decreased after 7 months. Both, the absence of comorbidities and having Covid-19 sickness between two doses of the vaccine influenced positively in prolonging the time of not having the disease.

Conclusions: Despite having up to 3 doses of the vaccine, which could increase the protection level against the disease, preventive measures should be strengthened because people possibly increase in confidence when vaccinated, especially in those with comorbidities, due to constant evolution of the virus and the emergence of new variants.