Abstract
Most currently available vaccines, particularly live vaccines, require the cold chain, as vaccine efficacy can be significantly hampered if they are not stored in a temperature range of 2–8 °C at all times. This necessity places a tremendous financial and logistical burden on vaccination programs, particularly in the developing world. The development of thermally stable vaccines can greatly alleviate this problem and, in turn, increase vaccine accessibility worldwide. In this paper, we detail a simple and cost-effective method for stabilizing live vaccines that uses FDA-approved materials. To this end, we dried enveloped DNA (Herpes Simplex Virus type 2) and RNA (Influenza A virus) viral vaccines in a pullulan and trehalose mixture. The results of these studies showed that the live-attenuated HSV-2 vaccine retained its efficacy for at least 2 months of storage at 40 °C, while the inactivated influenza vaccine was able to retain its immunogenicity for at least 3 months of storage at 40 °C. This work presents a simple approach that allows thermo-sensitive vaccines to be converted into thermo-stable vaccines that do not require refrigeration, thus contributing to the improvement of vaccine deployment throughout the world.
Highlights
Vaccination is a critical component of global health that saves millions of lives each year
As shown in Fig. 1(A), Herpes Simplex Virus type 2 (HSV-2) dried in the solution containing 10 wt% pullulan and 0.5 M trehalose (Matrix 3) most effectively maintained its viral titer, only losing 2.3 log plaque-forming units (PFU)/film after 12 weeks of storage
HSV-2 dried in the matrix containing only 0.5 M trehalose (Matrix 2) showed a titer loss of 3.6 log PFU/film after 12 weeks, while the HSV-2 that had been dried in the matrix containing 10 wt% pullulan (Matrix 1) was completely inactive after 7 days
Summary
Vaccination is a critical component of global health that saves millions of lives each year. Www.nature.com/scientificreports a human enterovirus type 71 vaccine to develop a self-biomineralized virus that could be stored for 1 week at 37 °C15 These thermally stable vaccines hold some promise, many still have short shelf lives (~7 days) when stored at elevated temperature (>37 °C). These challenges are compounded by the fact that, is the engineering of new vaccines labor intensive, but all newly developed vaccines must obtain governmental approval before they are deployed. Lovalenti et al successfully stabilized live-attenuated influenza vaccines in a sucrose-containing excipient using three drying methods: freeze drying, spray drying, and foam drying They found that, when the right excipient composition was used, foam drying produced the most thermally stable vaccine, with a shelf life of 4.5 months at 37 °C25. We demonstrate that the in vitro infectivity of these live viruses, and the in vivo immunogenicity of their corresponding vaccines, can be preserved for up to 3 months at 40 °C by drying them in a pullulan and trehalose mixture
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