Estimated quantification of residual volume in vaccines supplies and its impact on the Brazilian health system.

Between 2017 and 2021, the Brazilian Unified Health System (BUHS) administered a total of 527,903,302 doses of immunizations. Each immunization results in the presence of a residual volume (RV) due to syringe dead space (DS). The International Organization for Standardization 7886-1 allows a DS of up to 0.07mL in sterile single-use hypodermic syringes with volumes less than 5mL. This study aims to quantify the DS of immunization devices used in Brazil, study the best combinations of needles and syringes to minimize RV, estimate the number of wasted doses from 2017 to 2021, and evaluate the impact on the BUHS. Pneumococcal 10 vaccine with a 25x6mm needle and a regular 1mL syringe exhibited a significantly higher average RV (0.0826mL) and waste rate (14.42%). It was observed that for some intramuscular vaccines, there is less waste when using a 20x5.5mm needle compared to a 25x6mm needle. The use of syringes with plunger stoppers that penetrate the syringe barrel, denoted as low dead space syringes, results in less RV and an estimated difference in the waste rate of approximately 10% compared to the regular syringe. The estimated number of wasted doses from 2017 to 2021 by BUHS is approximately 32 million doses.