Effectiveness of vaccination can be estimated from post-vaccination data
Many countries have introduced HPV vaccination programs without establishing the baseline for HPV prevalence. Using prevalence of vaccine versus non-vaccine HPV types from a county where we had actual baseline data we made a reconstructed baseline. Methods were validated by computing the Bhattacharyya coefficient of divergence. Protective effectiveness where baseline data was missing could then be estimated using non-vaccine HPV type data to reconstruct the baseline.
Vaccine 1 May 2018 https://doi.org/10.1016/j.vaccine.2018.04.073