How has Gavi, the Vaccine Alliance, been able to be so successful in improving access to vaccines in developing countries? Select one: [Ola. Through partnerships, they were able to lower prices of vaccines by creating high-volume and stable demand in developing countries, giving them high purchasing power. b. They were able to fund the production of vaccines to increase the supply available at lower costs. O c. They have launched educational campaigns to improve awareness of the importance of vaccines to increase their uptake in developing countries. O d. They were donated stockpiles of unused routine childhood vaccines from neighbouring countries