Figure 2
Comparison of the MFI antibody levels to HPV-16 and HPV-18 at month 18 post vaccination among the vaccinated girls and the unvaccinated girls. The MFI levels for HPV-16 and HPV-18 among the vaccinated girls were over 20 and 15 times higher respectively among vaccinated than the unvaccinated girls. The central line represents the median MFI levels; above and below the median line in the box are the 75th and 25th centiles; the whiskers represent the upper and lower MFI values and the dots represent the outlier value. The outlier values were calculated using the z –scores (standardizing the data) with an absolute value of z as 1.96. There were 13/207(6.3%) and 11/197(5.5%) vaccinated and unvaccinated girls respectively with outlier values of antibody levels to HPV-16. For HPV-18, 11/207 (5.3%) and 6/197(3%) from the unvaccinated group had outlier values. For both HPV-16/18, the girls who had outlier values were comparable in terms of age and sexual activity.