The goal of this observational study is to learn about the immunity induced by the Qdenga® vaccine in vaccinees.

Participants that will receive the Dengue vaccine as part of their routine before a travel will be asked to undergo a blood sample at the time of administration of the first dose (T0), 24-48 hours after the first dose (T1) of the vaccine, immediately before the second dose (T2 ) and one to two months after the second dose (T3). Possibly a further sample will be collected within 2 years.

This is a non-profit, single-center, drug-based observational study whose primary objective is to characterize dengue-specific humoral and cellular immunity induced by the Qdenga® vaccine in vaccinees.

The study involves the enrollment of all pediatric subjects (age ≥ 4 years) and adults who present themselves at the DITM travel clinic for the administration of the Dengue vaccine; 402 patients are expected to be enrolled and will be asked to undergo a blood sample at the time of administration of the first dose (T0), 24-48 hours after the first dose (T1) of the vaccine, immediately before the second dose (T2 ) and one to two months after the second dose (T3). Possibly a further sample will be collected within 2 years (T4). The samples thus collected will be analyzed for the characterization of innate immunity, the characterization of cellular immunity and the characterization of the humoral response.

Inclusion Criteria:

• Subjects of both sexes presenting to the DITM to receive the anti-DENV vaccine whether or not they have had a history of prior DENV or other flaviviruses infection or a history of prior vaccination against other flaviviruses. These data will be recorded in the study CRF.
• Age >= 4 years.
• Signed informed consent.

Exclusion Criteria:

• Age < 4 years.
• Absence of signed informed consent.

All pediatric and adult subjects attending the travel clinic of the DITM for the administration of Dengue vaccine will be considered eligible.