Cervarix protects against two strains of the human papillomavirus, HPV16 and HPV18. HPV16 shows up in 90 percent of HPV infections. It also causes a subset of oropharyngeal cancers. In the past, drinking and smoking caused the majority of such throat cancers, but recently, doctors have seen increasing numbers of HPV-caused oropharyngeal cancers, especially among young adults in developed countries. Researchers now think viruses cause 30 percent of oropharyngeal cancers worldwide.