Most of the first generation microbicides were formulated as semi-solid systems, such as gels, tablets, films, or creams, and were designed to be applied to the vagina before every act of intercourse. However, vaginal rings have the potential to provide long-term controlled release of microbicide drugs. Long-acting formulations, like vaginal rings, are potentially advantageous since they could be easy to use, requiring replacement only once a month. This ease of use could prove very important to make sure that products are used properly. In 2010, the International Partnership for Microbicides began the first study in Africa to test the safety and acceptability of a vaginal ring containing dapivirine. Drugs might also be administered systemically through injectable or oral formulations known as PrEP. Injectable formulations may be desirable since they could be administered infrequently, possibly once a month. It is likely, however, that such products would need to be monitored closely and would be available only through prescription. This approach also carries the risk of emergence of ARV-resistant strains of HIV.