Long-Term HPV16/18 Antibody Responses Following a Single Dose of Nonavalent HPV Vaccine

Simplifying logistics and reducing costs in vaccination programs worldwide is a crucial goal, and achieving this for human papillomavirus (HPV) vaccination would be highly beneficial. A phase IIa trial investigated the potential of a single dose of the Gardasil9 vaccine in maintaining stable HPV type-specific antibody responses.

The trial involved 201 healthy girls and boys aged 9 to 11 years. The participants received an initial dose of the nonavalent vaccine at the beginning of the study, followed by a delayed dose at month 24 and an optional third dose at month 30. Throughout the study, blood samples were collected at various time points, including baseline, and at 6, 12, 18, 24, and 30 months after the initial dose, in order to measure HPV type-specific antibodies. The main focus was on assessing the serum HPV16 and HPV18 antibody responses.

In both girls and boys, the geometric mean concentrations of HPV16 and HPV18 antibodies showed a consistent pattern during the study. Initially, there was an increase in antibody levels at six months following vaccination. Subsequently, there was a decline between months 6 to 12. However, from months 12 to 24, the antibody levels remained stable and consistently high, reaching levels approximately 20 times higher for HPV16 and ten times higher for HPV18 compared to baseline.

This sustained and elevated antibody response observed throughout months 12, 18, and 24 (prior to the booster dose) indicates a robust and lasting immune response to the nonavalent HPV vaccine. Notably, both HPV16 and HPV18 antibody responses exhibited an anamnestic boosting effect at the 30-month mark after the delayed booster dose administered at 24 months.

These findings suggest that a single dose of the nonavalent HPV vaccine can induce a strong and durable immune response, with antibody levels remaining elevated for an extended period. Furthermore, the delayed booster dose administered after 24 months resulted in a significant immune response boost, highlighting the potential effectiveness of this vaccination approach.

Zeng Y, et al. HPV16/18 Antibody Responses After a Single Dose of Nonavalent HPV Vaccine. Pediatrics July 2023; 152 (1): e2022060301. 10.1542/peds.2022-060301