Vaccines, which are sensitive to both heat and cold, require temperature control during storage and transportation to ensure maximum potency on administration. Many of these vaccines are used in countries where temperature control throughout the chill chain is not always optimal, and hence the need arises for a low cost time temperature indicator that can give a clear visual indication as to the true state of the vaccine at the time of use. CoolVu meets this need by offering a range of tailored indicators designed to cover the lifetimes of the majority of vaccines currently used on a mass scale worldwide.