The rise in influenza-specific neutralizing antibody levels is proceeded by a burst of antigen-specific antibody secreting cells (ASC) or plasmablasts identified in peripheral blood approximately 5-10 days post immunization. Blood antigen-specific ASC may function as an immune marker of vaccine responses in comparison to the pre- and post-neutralizing titers; however, some have questioned whether there is adequate survival of ASC isolated from peripheral blood after freezing, making multi-center vaccine trials difficult. Here, we demonstrate similar frequencies of influenza-specific ASC from fresh and frozen peripheral blood mononuclear cells (PBMC). Influenza Hemagglutinin (HA) H1, H3, and H7-specific ASC IgG ELISpots frequencies were compared from the same fresh and frozen PBMC 7 days after 2006 Trivalent Influenza Vaccine (TIV) in 10 young healthy subjects. H1-, H3-, and H7-specific IgG ASC spots/106 from fresh PBMC on day 7 were 229 ± 341, 98 ± 90, and 6 ± 11 respectively. Total IgG ASC spots/million PBMC pre- and 7-day post-vaccination were 290 ± 188 (0.029% PBMC) and 1691 ± 836 (0.17% PBMC) respectively. There was no difference in the H1 -H3-, and total specific ASC IgG ELISpot frequencies from the fresh versus frozen PBMC on day 7 (p = 0.43, 0.28, 0.28 respectively). These results demonstrate feasibility of testing whether antigen-specific ASC from frozen PBMC are an early biomarker of long-term antibody responses in multi-center vaccine trials. © 2008 Elsevier B.V.