Clinical trials and systematic reviews demonstrate that the magnitude of the immune response—such as antibody geometric mean concentrations—varies depending on whether 1, 2, or 3 doses of the HPV vaccine are administered, even though single-dose regimens often maintain high seropositivity rates.
The retrieved papers consistently report that while single-dose HPV vaccination schedules (including Gardasil/Gardasil-9) can achieve high seropositivity for certain strains, the antibody concentration levels and overall immunogenicity vary between 1, 2, and 3-dose regimens. Therefore, the claim is supported by the literature.