Finally, studying booster immunizations for suboptimal responders and to maintain titers in those on immunosuppressants, and the optimal timing of vaccine administration are also areas that merit further investigation.
In our study, the booster rate was defined as the percentage of seronegative subjects receiving one booster dose.
Subjects were not offered the challenge dose if they had received investigational or non-registered medication or immunosuppressants during the conduct of the study or booster dose of hepatitis B vaccine outside the study context.
It is difficult to directly compare these results with other studies because booster vaccination recommendations vary by country [ 1, 7, 8, 18], studies use different case definitions [ 1, 18, 19], vaccine effectiveness decreases with age-associated decreases in vaccine-induced antibodies [ 5, 20, 21], and study subject characteristics may also differ considerably between studies.
This open-label extension booster study followed a Phase III study of 1206 adults who had received two 3.75 μg doses of primary AS03A-adjuvanted or non-adjuvanted H5N1 split-virus vaccine (A/Vietnam/1194/2004; clade 1) (NCT00449670).
Overall, few studies assessed boosters or program saturation, and evidence on multilevel versus single-level programs was inconclusive.
At the time of the study, an adolescent booster vaccination against pertussis, diphtheria and tetanus was recommended in Germany for all participants.
However, healthy volunteers in this study had received booster vaccination against Influenza, inducing high percentages of antibody secreting plasma cells in the peripheral blood of these individuals [12].
Prior recipients of candidate HIV DNA vaccines from VRC 004 (evaluation of a 4-plasmid DNA product) [20] and VRC 007 (evaluation of a 6-plasmid DNA product) [19] who consented to do so were assessed for eligibility to participate in a study evaluating a booster immunization with rAd5 [18].
The booster study took place between June and October 2006.
