Comparison of a semipermeable dressing bonded to an absorbent pad and a semipermeable dressing over a separate gauze pad for containment of vaccinia virus at the vaccination site.

OBJECTIVE: To compare the ability of 2 types of dressings to contain vaccinia virus after smallpox vaccination. DESIGN: Prospective, nonrandomized trial. SETTING: The smallpox vaccination clinic in a medium-sized military hospital. PARTICIPANTS: Ninety-seven active-duty military members who received smallpox vaccination in accordance with US Department of Defense and Centers for Disease Control and Prevention guidelines. METHODS: The first 40 participants enrolled were instructed to cover their vaccination sites with a semipermeable membrane placed over a separate gauze pad, and the subsequent 57 participants were given a semipermeable membrane bonded to an absorbent pad. Swab samples of the external surface of the dressing were collected 7 and 21 days after vaccination. Real-time quantitative polymerase chain reaction was used to detect vaccinia DNA in the samples. RESULTS: The rate of vaccinia DNA detection was significantly higher for samples obtained from vaccinees who were using the separate gauze and semipermeable membrane, compared with the vacinees who were using the gauze-impregnated semipermeable membrane (22% vs 2.2%; ; odds ratio, 12.3 [95% confidence interval, 1.4-567.4]). CONCLUSION: A gauze-impregnated semipermeable membrane more effectively reduced viral passage to the external surface of the dressing than did a semipermeable membrane placed over a separate gauze pad. Routine use of such dressings following smallpox vaccination might reduce the incidence of autoinoculation and secondary transmission.

Optimal bandaging of smallpox vaccination sites to decrease the potential for secondary vaccinia transmission without impairing lesion healing.

OBJECTIVE: To assess the optimal method for covering smallpox vaccination sites to prevent transmission of vaccinia. DESIGN: Randomized, nonblinded clinical trial. SETTING: Tertiary care medical center. PARTICIPANTS: Vaccinia-naive and vaccinia-experienced volunteers. INTERVENTIONS: After vaccination, study participants were randomized to receive 1 of 3 types of bandage: gauze, occlusive with gauze lining, or foam. Vaccination sites were assessed every 3 to 5 days until the lesion healed. During each visit, specimens were obtained from the vaccination site, the bandage surface before removal, and the index finger contralateral to the vaccination site and were cultured for vaccinia. Time to lesion healing was assessed. RESULTS: All 48 vaccinia-naive and 47 (87%) of 54 vaccinia-experienced participants developed a vesicle or pustule at the injection site 6-11 days after vaccination. Fourteen (14%) of 102 participants had bandage cultures positive for vaccinia. All but 1 of these vaccinia-positive cultures were of a bandage from participants randomized to the gauze bandage group, and all but 3 were of bandages from vaccinia-naive participants. No finger-specimen cultures were positive for vaccinia. One episode of neck autoinoculation occurred in a vaccinia-naive individual who had vaccinia recovered from his gauze bandage on multiple visits. The foam bandage was associated with more local adverse effects (skin irritation and induration). The time to healing did not differ among the bandage groups. CONCLUSIONS: The potential for transmission of vaccinia from a vaccination site is greater if the site is covered by gauze than if it is covered by occlusive or foam bandages. Use of an occlusive bandage with a gauze lining is the best choice for coverage of smallpox vaccination sites because of a reduced potential for vaccinia transmission and a lower reactogenicity rate. Bandage choice did not affect vaccination lesion healing.

Frequency of vaccinia virus isolation on semipermeable versus nonocclusive dressings covering smallpox vaccination sites in hospital personnel.

BACKGROUND: The Centers for Disease Control and Prevention recommends a semipermeable occlusive dressing for hospital workers who receive smallpox vaccination. OBJECTIVE: The study was designed to determine the frequency of vaccinia virus isolation from the outer surface of semipermeable dressings and to compare the prevalence of vaccinia virus on the outer surface of semipermeable dressings with its prevalence on the outer surface of nonocclusive dressings. METHODS: A prospective, observational study was conducted on hospital employees who received smallpox vaccination at a military academic medical center. Subjects were instructed to wear a semipermeable dressing if they had direct patient contact. Employees without direct patient care had the option of wearing a semipermeable dressing or a nonocclusive dressing. Prior to a programmed dressing change, the outer surface of the bandage site was swabbed and cultured for virus. Samples were considered positive when cytopathic effects were observed, with results confirmed as vaccinia by polymerase chain reaction. RESULTS: A total of 212 cultures were obtained from 93 subjects. All cultures directly obtained from active lesions were positive (13/13). Positive cultures were obtained from 7% (10/135) of the semipermeable dressings and 23% (15/64) of the nonocclusive dressings (P <.05). Ten percent (8/79) of the semipermeable dressings with purulent exudate observed underneath the bandage were culture positive, compared with 4% (2/56) of semipermeable dressings with no purulent exudate observed underneath the bandage (P=.19). CONCLUSIONS: Compared with nonocclusive dressings, the semipermeable dressing reduced, but did not eliminate, the frequency with which vaccinia virus was cultured from the surface of the dressing. Virus was present, but only rarely, on the dressing surface in the absence of purulent exudate under the semipermeable dressings.