Recombinant vesicular stomatitis virus vector vaccines for WHO blueprint priority pathogens

Fathi, Anahita; Dahlke, Christine; Addo, Marylyn M.

ion regimen applied during the recent DRC EBOV outbreaks including a total of 93,965 vaccinated individuals and reported an estimated vaccine efficacy of 97.5%, thus strongly supporting the findings of the phase III trial. 60 Stability of the vaccine In the context of the deployment of VSV-EBOV in the field setting, the storage of the vaccine, which must be kept at a temperature of −70°C maximum, remains a challenge. The establishment and maintenance of cold chains in often rural surroundings with suboptimal infrastructure has been difficult. 61 To date, stability data remain scarce, yet one study found that the vaccine stayed stable with comparable viral titers for 7 days when stored at +4°C. 62 In a guinea-pig challenge model, vaccination with VSV-EBOV conferred protection from disease even when stored in various suboptimal conditions over 7 days (4°C, room temperature, 32°C, or three cycles of freeze-thawing from −80°C to room temperature), and only the vaccine kept at 32°C showed a significant reduction in virus titer. 63 The data indicate that short-term interruptions of the cold chain may be tolerated without affecting vaccine efficacy.