Background: While vaccines provide substantial protection against COVID-19, breakthrough infections remain a concern. This study aimed to determine the Incidence rate of post-vaccination COVID-19 infections among healthcare workers at teaching hospitals in Gorgan, Northeast Iran between 2020 and 2021.
Methods: In this cross-sectional study, we enrolled all 527 healthcare workers who had received at least one dose of non-mRNA COVID-19 vaccines. Vaccination data were systematically recorded and analyzed. COVID-19 infection was laboratory-confirmed by RT-PCR testing.
Results: The mean age of participants was 35.3±9.8 years. Breakthrough infections occurred in 255 participants (48.4%) after primary vaccination (First and second doses) and in 36 cases (6.83%) following booster doses. Incidence rates were significantly higher among internal medicine and infectious disease staff (p=0.006). Temporal analysis revealed peak infection incidence within 4 months post-primary vaccination, with the lowest rates observed >4 months post-booster administration.
Conclusion: While breakthrough infections occurred in a substantial proportion of participants after primary vaccination, booster doses were associated with significantly lower infection rates. Further research is needed to assess the impact of vaccination status on disease severity.