Evidence of vaccinia dissemination despite lack of major reaction following smallpox vaccination

Wilfred P. Delacruz, Michael R. Savona, Jennifer A. Thornton, Patrick J. Danaher

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Following vaccinia vaccination, vesicle formation at the site occurs in 95% of primary vaccinees and is thought to indicate virus replication and vaccine efficacy. Little is known about virus replication and immune response in those who do not develop a vesicle. We used PCR to detect vaccinia in various sites following receipt of the smallpox vaccine in those with and without vesicle formation. Among 80 participants, 74 developed and 6 failed to develop a vesicle. Vaccinia DNA was detected in the blood, in the oropharynx, on the dressing, and on the hands of 5%, 11%, 4%, and 0% of those with vesicle formation and of 33%, 17%, 0%, and 17% of those without vesicle formation, respectively (p > 0.05 for each site). The detection of systemic vaccinia DNA in vaccinees without vesicle formation challenges the current understanding that lack of vesicle formation indicates lack of virus replication, the prerequisite to immune response.

Original languageEnglish (US)
Pages (from-to)1589-1592
Number of pages4
Issue number7
StatePublished - Feb 11 2020


  • Immunity
  • Major reaction
  • Polymerase chain reaction
  • Smallpox vaccination
  • Vaccinia

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • General Immunology and Microbiology
  • Infectious Diseases
  • Molecular Medicine
  • General Veterinary


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