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

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.

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.

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.

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.