Kaissar Tabynov, Berik Khairullin, Zhailaubay Kydyrbayev, Nurlan Sandybayev, Marina Stukova, Marianna Erofeeva, Anna Polina Shurygina, Oleg Kiselev, Seidigapbar Mamadaliev and Abylai Sansyzbay
We performed a randomized, blinded, dose-dependent placebo-controlled phase I clinical study of single administration of Refluvac®, a monovalent inactivated whole-virion vaccine against pandemic influenza А (Н1N1) pdm09 containing aluminum adjuvant, in healthy volunteers aged 18-60. Single intramuscular injection at doses of 3.75, 7.5, or 15.0 μg hemagglutinin (НА) identified no safety issues in adult volunteers (n=12 per group); no severe or serious vaccination-related adverse events were observed. Only mild/moderate local adverse events (n= 3/12, 25% in 7.5 μg НА arm,) and one moderate systemic reaction (n=1/12, 8.3% in 15.0 μg НА arm) were observed. In volunteers vaccinated at 3.75 μg HA, the proportion of subjects with 4-fold seroconversion was 75%, the level of seroprotection was also 75%, the antibody titer increase was 10.7-fold, and the geometric mean titer (GMT) of antibodies to А/H1N1pdm09 was 53.4; for the 7.5 μg HA dose, the proportion of 4-fold seroconversion was 75%, the antibody titer increase was 32.0-fold, the GMT was 160.0, and the level of seroprotection was 75%. When administered at a higher dose (15 μg HA), the proportion of subjects with protective antibody titers increased from 75% to 83%; however, the GMT and antibody titer increase were not significantly different (P>0.05) to the group vaccinated at 7.5 μg HA. Phase II clinical studies of the 3.75 and 7.5 μg HA doses of Refluvac® vaccine should be performed in a larger cohort of healthy volunteers aged 18-60. The effective immunogenicity of low doses of Refluvac® vaccine may enable increased production of pandemic influenza vaccines, and thus provide more people with a safe, effective vaccine.