Smallpox revaccination of 21000 first responders in Israel: lessons learned.

OBJECTIVES: Between July 2002 and April 2003, over 21000 individuals were revaccinated against smallpox by the Israeli Ministry of Health. The objectives of the campaign were to create an immunized core of first responders, to review vaccination techniques, and to produce vaccinia immune globulin (VIG). METHODS: The Lister strain of vaccinia virus was used at a concentration of approximately 10(7) pock-forming units (PFU)/ml, and was administered by the multiple-puncture technique. The revaccinees were from varied ethnic backgrounds, almost all were aged 25-64 years, and all participants had been vaccinated against smallpox in the past. RESULTS: The proportion of clinical take was 66.1% (95% CI: 65.2%, 67.0%), similar to past vaccination programs when take also occurred in approximately two thirds of vaccinees. An antibody response occurred in 77.7% (95% CI: 74.8%, 80.6%) of all revaccinees: 94.4% (95% CI: 91.8%, 96.3%) of those with clinical take and 56.6% (95% CI: 51.3%, 61.8%) of those without clinical take. The most common side effects corresponded to symptoms of non-specific viral diseases, and only a few revaccinees reported serious side effects. CONCLUSIONS: The campaign achieved all its basic goals and provided useful lessons for any mass-vaccination programs that might be necessary in the future.

Beveled needle technique is not associated with low "take" rates in Israeli smallpox revaccination campaign.

BACKGROUND: In its first large-scale smallpox vaccination campaign in the 20(th) century, Israel has experienced an exceptionally high rate of failure to achieve clinical take following vaccination. It was hypothesized that this failure rates might be attributed to the unique vaccination technique adopted in Israel, of using beveled needles rather than bifurcated needles. MATERIALS AND METHODS: We retrospectively identified two cohorts vaccinated in the defined dates during the Israeli revaccination campaign, in which beveled needles and bifurcated needles were used alternately, and studied the impact of different covariates on clinical vaccination outcome measures. RESULTS: Of 116 subjects that were vaccinated within the defined dates, 46 were vaccinated using bifurcated needles, and 70 by beveled needles. 'Take' rates in subjects vaccinated up to 20 years earlier was 77.5%, compared with 97.2% among those vaccinated in the more distant past (p = 0.001). In multivariate analyses, vaccination 'take' was independently associated with a shorter time from previous vaccination (p = 0.013), but not with gender, birth country, vaccinator or the vaccination technique used. CONCLUSIONS: The low take rates observed in the Israeli smallpox revaccination campaign could not be attributed to the unique local vaccination technique, and was most likely induced by a higher rate of residual immunity among vaccinees, compared with the US, as well as by the lower vaccine concentrations used in Israel. In countries and circumstances when bifurcated needles are not sufficiently available, the beveled needle technique may be considered an appropriate alternative.