Letters Section Editor: Robert M. Golub, MD, Senior Editor.
To the Editor: In their Research Letter, Dr Savona and colleagues1 reported on the detection of vaccinia virus DNA in blood and oropharyngeal specimens by polymerase chain reaction (PCR) assay. We believe that to put their results into context, results of other studies must also be considered.
Two similar studies2,3 conducted at Walter Reed Army Medical Center in 2004 used 3 methods to detect vaccinia virus: PCR,4 electrochemiluminescence, and viral culture. The first study2 included 220 blood samples from 28 participants. The second study3 tested oropharyngeal swabs in 801 samples from 144 participants. All samples in each study were negative. Contributing to the discordance between Savona et al and the Walter Reed studies are the primers used, the sampling time points, the amount of plasma from which the DNA was extracted for PCR, and the additional testing conducted on the Walter Reed specimens.
Klote MM, Engler RJM, Martin BL, Cummings JF, Wortmann GW, Ludwig GV. Vaccinia DNA in Blood After Smallpox Vaccination. JAMA. 2006;296(11):1350-1352. doi:10.1001/jama.296.11.1350-c