Geraldine Taylor and colleagues at The Pirbright Institute in the United Kingdom will develop a thermo-tolerant vaccine based on human adenovirus 5 (Ad5) against peste des petits ruminants (PPR), a highly contagious disease found in goats and sheep, that enables the distinction between infected and vaccinated animals (known as DIVA vaccines). Current live attenuated vaccines require cold storage, which is unavailable in many developing countries, and vaccinated animals cannot be differentiated from infected animals, complicating disease control efforts.