After the first vaccination, antibody responses were higher with higher dose, i.e. 250 μg. At day 29, enzyme-linked immunosorbent assay anti–S-2P antibody geometric mean titer [GMT] is 40,227 in the 25 μg group, 109,209 in the 100 μg group, and 213,526 in the 250 μg group.
After the second vaccination, the titers increased. At day 57, GMT is 299,751, 782,719, and 1,192,154, respectively for the three dose groups.
Serum-neutralizing activity was detected by two methods : PsVNA responses were identified in serum samples from all participants after the second vaccination and PRNT assay with a titre reducing infectivity by 80% (PNRT80) appears at day 43 in all patients.
Binding antibody IgG geometric mean titers (GMTs) to S-2P increased rapidly after the first vaccination, with seroconversion in all participants by day 15, in a dose-dependent manner to the first and second vaccinations.
The main side effects reported are mild to moderate in the majority of patients: fatigue, chills, headache, myalgia, and pain at the injection site. 5 participants (33%) in the 25 μg group, 10 (67%) in the 100 μg group, and 8 (53%) in the 250 μg group.
Systemic adverse events were most frequently seen after the second vaccination in 7 of 13 participants (54%) in the 25 μg group, 15 (100%) in the 100 μg group, 14 (100%) in the 250 μg group.
More serious side effects are reported with the highest dose, i.e. 250 μg and occur in only 3 patients (21%).
The report results are only preliminary, as the 250 μg dose data for PRNT assay are missing of the three doses studied (25 μg, 100 μg and 250 μg).
The 45 patients are healthy adult volunteers, 18 to 55 years of age, not representative of the extreme age groups (young and elderly subjects).
The black population is under-represented only in the 100 μg group (2 patients, i.e. 13%).
3 patients did not strictly follow the protocol.
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