Lymph Node Activation by Pet/ct Following Vaccination With Licensed Vaccines for Human Papillomaviruses

While PET using 18F-FDG is most commonly used for imaging malignant tumors, vaccination is known to cause transient inflammation of lymph nodesinducing positive findings on 18F-FDG PET scans. The pattern, magnitude, and duration of lymph nodeactivation following vaccination have not been clearly defined. Furthermore, the addition of adjuvants to vaccines can further enhance the immune response. The presented study was designed to define lymph nodeactivation following administration of the Food and Drug Administration–licensed human papillomavirus vaccines, Cervarixand Gardasil, which contain similar antigens with different adjuvants. Twenty-seven women aged 18 to 25 years were randomized to receive either Cervarixor Gardasilin the clinical trial VRC 900. Fifteen subjects participated in the PET/CT portion of the trial and received scans of lymph nodeactivation at prevaccination and “1 week” (8–14 days) and “1 month” (23–36 days) after the first or third vaccination. PET/CT scans revealed that all vaccine recipients had ipsilateral axillary lymph nodeactivity. Three of 4 Cervarixrecipients also showed contralateral lymph nodeactivity 1 month after the first vaccination. For both Cervarixand Gardasil, the SUV activity resolved over time, with activity extended up to day 37 after the first and third vaccinations. Following intramuscular vaccination, there were no major differences between duration of uptake and intensity of SUV between Cervarixand Gardasilrecipients in ipsilateral axillary lymph nodes. Contralateral node activation was detected up to 1 month after the first vaccination in Cervarixrecipients only, possibly reflecting differences in vaccine adjuvant formulation.