This study forms part of an integrated, multi-study effort to identify potential biomarkers of reactogenicity to vaccines. We have selected PET-CT as it is in routine clinical use and has been serendipitously shown to image lymph nodes and injection site inflammation after immunisation.The study's objectives are exploratory:

1. To methodically characterise relative anatomical distribution and intensity of post-immunisation innate immune activation visualised by PET-CT after immunisation with adjuvanted and non-adjuvanted vaccines.
2. To correlate PET/CT changes with diary card recorded symptoms of reactogenicity.

Inclusion Criteria:

1. Able to read and understand the informed consent form (ICF), and understand study procedures
2. Signed the ICF
3. Healthy male aged 18'Äì55 years inclusive
4. BMI 19'Äì27 kg/m2
5. Pre-immunised with hepatitis B vaccine on the basis of immunisation history if Fendrix or Engerix B is to be the study vaccine
6. Available for follow-up for the duration of the study
7. Is, in the opinion of the investigator, healthy on the basis of a medical history, symptom directed medical examination and vital signs
8. Have not undergone research radiation exposures, and agree to avoid such exposures, for 12 months before/after this study
9. Be willing to avoid vigorous exercise or contact sports between vaccination and PET scan (e.g. gym workouts, prolonged cycling, rowing, martial arts or rugby)

Exclusion Criteria:

1. History of hypersensitivity to any of the vaccine components or a history of any allergy that in the opinion of the investigator would contraindicate participant participation
2. Use of steroids or immunosuppressive/immunomodulating drugs either orally or parenterally within 3 months of the PET scan. (Topical/ocular/nasal/inhaled steroids are allowed.)
3. Expression of only TSPO with low-affinity to PBR28, on the basis of TSPO genotype
4. Currently participating in a clinical study with a drug or device
5. Any condition that, in the investigator'Äôs opinion, compromises the participant'Äôs ability to meet protocol requirements or to complete the study
6. Unable to read and speak English to a fluency level adequate for the full comprehension of procedures required in participation and consent