Study design.

<p>Sera from individuals were randomly selected by DoDSR staff based on the following inclusion criteria: the sample must be banked sera stored in the DoDSR, with available specimens at the requisite time points and with full documentation of smallpox immunization on record for the donor. Samples were excluded if the smallpox vaccination status was unknown, the sample was positive for HIV infection, or there was inadequate sera volume.</p

Influence of age at immunization on immunity duration.

<p>Anti-vaccinia ELISA titers are shown for the Dryvax® groups of the present study of military personnel vaccinated as adults in comparison to results from screening of civilian participants in a separate study (RV 158) who were known to be vaccinated with Dryvax® as children (right panel). The geometric mean titers and percent positive responders per group are indicated. Comparison between the most distal time points from vaccination were done via Mann-Whitney unpaired t-test.</p

Neutralization of MVA-GFP infection of primary human dendritic cells.

<p>(A) Neutralization curves for each group are shown as the mean ± SEM of all serum samples at various dilutions. (B) Curves were analyzed by non-linear regression sigmoidal dose response curve fitting to determine the ID50 of each sample. Geometric mean and percent positive are indicated for each group. The p value was generated by Mann-Whitney unpaired t-test of each group compared to the negative control (vaccinia-naïve) group.</p