
Three immunizations with a bivalent human papillomavirus (HPV)-16/18 L1 virus-like particle AS04 vaccine safely induces sustained high levels of antibodies that provide long-term protection against HPV-16 and -18 infection and associated cervical lesions and possibly against HPV 45 and HPV 31-the third and fourth most common HPV types associated with cervical cancer-for up to 4.5 years.