Clinical responses to undiluted and diluted smallpox vaccine.
BACKGROUND
To evaluate the potential to increase the supply of smallpox vaccine (vaccinia virus), we compared the response to vaccination with 10(8.1), 10(7.2), and 10(7.0) plaque-forming units (pfu) of vaccinia virus per milliliter.


METHODS
In this randomized, single-blind, prospective study, 680 adults who had not been previously immunized were inoculated intradermally with undiluted vaccine (mean titer, 10(8.1) pfu per milliliter), a 1:5 dilution, or a 1:10 dilution of vaccinia virus with use of a bifurcated needle, and the site was covered with a semipermeable dressing. Subjects were monitored for vesicle formation (an indicator of the success of vaccination) and adverse events for 56 days after immunization.


RESULTS
Success rates did not differ significantly among the groups and ranged from 97.1 to 99.1 percent after the first vaccination. Both the undiluted and diluted vaccines were reactogenic. In addition to the formation of pustules, common adverse events included the formation of satellite lesions, regional lymphadenopathy, fever, headache, nausea, muscle aches, fatigue, and chills consistent with the presence of an acute viral illness. Generalized and localized rashes, including two cases of erythema multiforme, were also observed.


CONCLUSIONS
When given by a bifurcated needle, vaccinia virus vaccine can be diluted to a titer as low as 10(7.0) pfu per milliliter (approximately 10,000 pfu per dose) and induce local viral replication and vesicle formation in more than 97 percent of persons.
Frey
Sharon E
SE
Department of Medicine, National Institute of Allergy and Infectious Diseases Vaccine and Treatment Evaluation Unit, Saint Louis University School of Medicine, St. Louis, USA.
Couch
Robert B
RB
Tacket
Carol O
CO
Treanor
John J
JJ
Wolff
Mark
M
Newman
Frances K
FK
Atmar
Robert L
RL
Edelman
Robert
R
Nolan
Carrie M
CM
Belshe
Robert B
RB
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D004355:Drug Stability; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D011446:Prospective Studies; D016037:Single-Blind Method; D012899:Smallpox / Q000517:prevention & control*; D012900:Smallpox Vaccine / Q000008:administration & dosage* / Q000009:adverse effects; D012901:Variola virus / Q000254:growth & development* / Q000302:isolation & purification; D014779:Virus Replication
D012900:Smallpox Vaccine