The SARS-CoV-2 pandemic seriously affected international flights. Due to the availability of effective vaccines against COVID-19 and in order to decrease travel restrictions, the quarantine requirement was eliminated for people who had already had at least 14 days of their second dose of the vaccine. All PCR test data for residents arriving on international flights, regardless of departure country and vaccination status, was analyzed throughout the program (February 18 to April 26, 2021). We evaluated whether vaccines (Pfizer-BioNTech or Moderna) and previous infection were associated with a lower risk of PCR testing positive. Complete vaccination was defined as at least 14 days after the second dose before the PCR test at the airport. Reinfection was defined as the first positive PCR smear at least 90 days after a previous infection. People with a positive PCR swab less than 90 days before the airport PCR test and vaccinated people who received only 1 dose or who did not show up at least 14 days after the second dose were excluded. In total, 261849 people (75.1% men) were tested by PCR, 31190 fully vaccinated individuals and 215901 individuals without vaccination record or previous infection giving a PCR positivity was 0.82% and 3.74% respectively. Vaccination and prior infection were associated with a reduced risk of PCR positivity, however, both vaccine immunity and natural immunity were imperfect, and breakthrough infections were recorded.