Effectiveness of HPV vaccine as part of national immunization program for preventing HPV infection in Thai schoolgirls after seven years post-vaccination.

Thailand introduced a two-dose regimen of bivalent HPV vaccines for Grade 5 schoolgirls, approximately 11 years old, initially piloted in Ayutthaya province in 2014, and nationwide under the National Immunization Program (NIP) in 2017. This cross-sectional, case-control study evaluated the vaccine effectiveness in schoolgirls 7 years after a two-dose administration. Between May and June 2023, 211 grade 12 female students from Ayutthaya, who received the two-dose bivalent HPV vaccine CERVARIX (HPV types 16 and 18), and 376 grade 12 students from Nakhon Pathom who did not receive the HPV vaccine, were enrolled.