(334) Comparative Seroprevalence Analysis of COVID-19 Vaccination Strategies: Insights from a Multicenter Study in Castilla-Leon, Spain

Background: Although vaccination has proven to be one of the most important tools to control the COVID-19 pandemic, it was necessary to know the antibody response generated after immunization with the different vaccination protocols against COVID-19 in the general population.

Objectives: To compare the seroprevalence generated between the different vaccination strategies.

Methods:

Design: We conducted an observational, descriptive, cross-sectional, and multicenter study at the 121 community pharmacies forming the Sentinel Network of Castilla-Leon (Spain). In the study, we analyzed the safety profile and immunogenicity produced after administering vaccines against SARS-COV-2 in the general population of Castilla-Leon.
Setting: During the study, specific antibodies against SARS-COV-2 (seroprevalence) produced after vaccination in 1,654 individuals from the general population of Castilla-Leon were analyzed. This sampling distribution was carried out according to the age of the individuals following the population age pattern presented by the autonomous region of Castilla-Leon.
Main outcome measures: The presence of antibodies, Ab, both IgM and IgG against SARS-CoV-2 in the study samples was analyzed using rapid detection tests.
Statistical analysis: The data on the distribution of normality of the different quantitative variables analyzed were summarized as mean and standard deviation (SD). The seroprevalence results for each patient have been analyzed as IgG positive or negative.

Results: Our data indicate that 92.3% of the vaccinated population had IgG antibodies against COVID-19. This percentage was significantly higher than the percentage found in the non-vaccinated population, which was 17.9%. In this population (not vaccinated), 34% passed COVID-19, and 45% of them still had antibodies against the infection. The impact on seroprevalence of the 6 different vaccination strategies was also examined. All the complete vaccination protocols that use homologous immunization with Pfizer, Moderna, or AstraZeneca; together with the heterologous combination protocols, mixing some of these vaccines, generated a humoral response in more than 90% of the strategies. However, the administration of a single dose of the Janssen vaccine generated a significantly lower response than the rest of the immunization protocols (60.5%).

Conclusions: These results demonstrate that community pharmacies can generate a highly effective rapid response network when epidemiological data or the efficacy of the drug is urgently required. The network of sentinel Pharmacies in Castilla-Leon (Spain) is an example of this type of work protocol.