Relationship between SARS-CoV-2 vaccination and cases, program breakthrough cases, and deaths in Dois Vizinhos, Paraná, Brazil.

Several vaccines have been produced in 2 years of the COVID-19 pandemic to control the infection outbreak. This study demonstrated the success of vaccination in controlling COVID-19 cases and deaths in a small city (41 424 people) with a low population density in Brazil. This study was based on a 1-year dataset since the application of the first dose in January 2021. The results show a reduction in positive cases and deaths as the vaccination coverage increased in the city, mainly after 15 000 inhabitants were vaccinated (35.21% of the population) in July 2021. At the time, 49.06% of administered vaccines were ChAdOx1-S recombinant, 39.80% inactivated SARS-CoV-2 virus (CZ02 strain), 9.70% Tozinameran, and 1.44% Ad26.COV2-S recombinant. From August 2021, a marked reduction in daily positive cases and deaths was observed, and incidence (≤2.49 per 1000 inhabitants) and mortality (≤0.02 per 1000 inhabitants) rates remained stabilized until January 2022, when a new outbreak occurred upon the emergence of the Omicron variant. However, the mortality rate (0.07 per 1000 inhabitants) remained low regardless of the Omicron high incidence rate (68.41 per 1000 inhabitants). These data demonstrate the COVID-19 vaccination effectiveness with a threshold of 35.21% of the population vaccinated in this city model.