Researchers estimated the percent coverage by session size range if a healthcare worker opens a vial only for sessions where 50% of doses will be used (i.e., only when at least five eligible children are present). With large session sizes, the coverage differences are small. But in areas where sessions are between 1-10 children—as in many “last-mile” settings—a 50% “opening threshold” will decrease coverage to 60% even when the needed vaccines are technically available. Similarly, in a hypothetical scenario, researchers found that cost per dose administered is higher for a multi-dose vial when sessions are small, and that relationship quickly reverses as session sizes increase. Regarding safety, researchers noted that increasing the doses per container increases the opportunity for user error, which may raise the likelihood of non-sterile injections and injections with expired vaccines.