Background and Objective:
The real-world effectiveness and duration of anti-COVID19 vaccine’s protection from reinfections in the pediatric population (5-11 years) has yet to be determined. Groups with different primary immunization were compared, in terms of duration of immunity and effectiveness for COVID19 reinfections.

Methods:
In this retrospective population analysis, we analyzed data from the vaccination registry and Infections Regional Information System of Apulia region (Southern Italy) for birth cohorts 2011-2017 from 31/12/2020 to 02/12/2022. We identified three groups based on the primary immunization schedule: subjects 5-11 years old vaccinated with two doses (vaccine immunity), not vaccinated with a history of SARS-CoV2 infection (natural immunity) and individuals with a combination of both (hybrid immunity). Subjects with a SARS-CoV2 infection occurring within the first 14 days from the primary immunization course were excluded. COVID19 reinfection was defined as a positive swab after 90 days from previous infection. Data were analized using R and compared using chi-square test.

Results:
A total of 30,997 children were included (15,064 females, 15,933 males; mean age 8.31.9); 22,073 (71.2%) children were infected from SARS-CoV2 at least once and 1,533 (4.9%) had a COVID19 reinfection. Cases of reinfections and mean distance since COVID19 infection were in the vaccine immunity group 192 (1.12%) 87.855.8 days; in the natural immunity group 1,254 (9,5%) 21495.9 days; and hybrid immunity group 87 (12.3%) 155.485.5 days. We observed a significant relationship between natural immunity group and COVID19 reinfections (X =1142; p