Scientists have found additives that, at low concentrations, extend the life of vaccines at room temperature.
High levels of sugar stabilize virus particles in vaccines, but the mechanism was unclear. Francesco Stellacci at the Swiss Federal Institute of Technology in Lausanne and his colleagues studied how sucrose and two other additive candidates affect viruses over time. They found that low concentrations of the polymer polyethylene glycol and gold nanoparticles mimicked the effects of sugar, increasing the half-life of a virus called adenovirus type 5 from 7 days to more than 30 days at room temperature.
The team concludes that high levels of sugar keep viruses structurally intact mainly by making the vaccines more viscous. For the other additives, particles act directly on the virus's protein shell to prevent it from degrading. The findings should aid in the design of better additives, which could reduce the high cost of keeping vaccines cold to maintain their potency during distribution.