Introduction: By July 2023, Brazil had administered approximately 540 million COVID-19 vaccine doses. This study aimed to quantify wasted doses resulting from dead space in vaccine supplies.
Methods: The vaccine supply was initially weighed, filled with distilled water, and expelled to simulate administration. Weighing it again after the application determined the dead space volume. Descriptive analyses calculated the waste rate/wasted dose count.
Results: The estimated total number of wasted vaccine doses using supplies with the lowest dead space was 62,097,338.
Conclusions: Syringe dead space is a crucial factor in dose wastage, directly influencing the number of wasted doses.