SAN DIEGO, CA— Results from a Phase 2 study showed that the 5555 formulation of tetravalent dengue vaccine elicits the highest serpositivity rates and balanced response against all four serotypes with a satisfactory safety profile, as reported by Gustavo H Dayan, MD, from Sanofi Pasteur, Swiftwater, PA, at IDWeek 2012.

A tetravalent dengue vaccine comprising recombinant, live, attenuated viruses, one per serotype is being developed and has entered Phase 3. Dayan and colleagues conducted a Phase 2 randomized, double-blind study during 2008–2009 to describe the safety and immunogenicity of three different formulations of the tetravalent dengue vaccine. A total of 255 patients (aged 18–45 years) were randomized to receive 3 doses, 6 months apart of 3 different vaccine formulations: 5 log10 TCID50/serotype (5555; n=101)); 5 log10 TCID/serotype 1, 2, 3 and 3 log10 TCID50/serotype 4 (5553; n=101); and 4 log10 CCID50/serotype (4444; no=53). Neutralizing antibody titers were determined post-hoc using PRNT50 assay in serum at baseline and one month after each vaccination. Safety methods included daily recording of solicited injection site reactions for seven days, and solicited systemic reactions for 14 days after each vaccine dose.

Data showed that one month after the third dose, seropositivity rates (titer >10 [1/dil]) for serotypes 1–4 were 71%, 84%, 89%, and 94% for group 5555; 84%, 89%, 99%, 69% for group 5553; and 64%, 78%, 82%, and 93% for group 4444. Percentage of positive seropositive subjects to all four types after the third dose was 63% for group 5555, 59% for group 5553, and 53% for group 4444. In addition, no vaccine-related serious adverse events were reported.

Dayan and colleagues were able to conclude that the 5555 formulation of tetravalent dengue vaccine elicited the highest and most balanced response against all four serotypes. “The safety and immunogenicity data obtained supports the use of this formulation in Phase 3 clinical trials,” noted Dayan.