Vaccination against oncogenic human papillomavirus (HPV) types is an intervention for cervical cancer prevention. Despite there being a relatively long period of time since the beginning of clinical use of HPV vaccines no evidence-base data is available on the need of a boost vaccination. We investigated one-year post-vaccination antibody responses against HPV 16/18 by detection of IgG and IgA HPV-specific antibodies in cervical secretion samples and serum.
This study was designed to describe the course of IgG/IgA responses in cervical secretions and in serum one year after the first dose of intramuscular administration of the HPV16/18 AS04-adjuvant vaccine. Blood and cervical mucus samples were collected for immunologic assays, 7 months after the first doses and 1 year following the last boost vaccination (month 7) by enzyme linked immunosorbent assay (ELISA). The detection of IgG and IgA anti-HPV/VLP was developed for this purpose.
It was observed that approximately 100% of the IgG serum samples reacted when the antigen was present in the first dilution of both collections. The positivity, however, decreases, according to the dilutions. Regarding IgA reactivity in serum, initial conversion was observed in 95% at month 7 of vaccination and 79% after 1 year. Similar results can be seen in the mucus samples with a higher positivity at month 7 and decreasing after 1 year, lower levels of IgG and IgA antibody were detected in the cervical mucus (33%) and 29%, respectively, after 1 year of vaccination. The median absorbance detected in serum samples for IgG and IgA anti-HPV-VLP antibodies was significantly higher at 7 months after vaccination, in the dilutions 1:100, 1:1.000, 1:10.000 and 1:10, 1:100, respectively, when compared to 1 year after vaccination (P<0.0001). The median absorbance detected in cervical mucus samples was significantly higher at 7 months after vaccination, in the dilutions 1:100, 1:1.000 and 1:10 for anti-HPV-VLP IgG and IgA, respectively, when compared to 1 year after, with 1:100 and 1:10, for IgG and IgA respectively (P< 0.0001). In serum and cervical mucus samples, the median absorbance was significantly higher 7 months after vaccination and it is possible to see the decrease at 1 year after, according to dilutions.
One year after the first dose, the immune responses induced by the HPV-16/18 AS04-adjuvant vaccine were significantly decreased in cervical secretion samples and serum when compared to seven months after the first dose. A possible vaccine booster may be necessary. However, longer follow-up studies are necessary to assess the need for booster doses after primary vaccination with 2 as well as with 3 doses.