those with contraindications were intending to take the vaccine (Everett et al., 2002). In so far as it is possible, this should be avoided. The committee thus spent considerable effort considering alternative means of screening, which might be more effective than simple provision of information. Ideally, the vaccine would not be administered at the place of work, to avoid peer pressure, and peer knowledge, about the decision made by a potential vaccinee, though this may be unavoidable in phase I.

Commonly used blood donation forms provide multiple confidential opportunities for donors to opt-out of the blood donation process if they believe that their blood is not safe to be given to someone else. The committee believes this model could be considered for the pre-event smallpox vaccination program. Vaccinees should not feel any pressure to receive the vaccine, for fear that a medical condition that they do not want to disclose may be discovered by the vaccination clinic or potentially, by their employer. By offering multiple opportunities to optout of vaccination, CDC can help ensure that the program is carried out in the most ethical manner possible. The committee recommends that CDC consider using the blood-donation opt-out and informed consent processes as models for the pre-event smallpox vaccination program.

Reasons for Declining Vaccine

Potential vaccinees will have different reasons for declining the vaccine, ranging from personal contraindications, contraindications in household and other close contacts, fear about adverse reactions of the vaccine, or apprehension about the benefit of receiving the vaccine. The committee recommends that CDC collect data on the reasons why potential vaccinees choose not to be vaccinated.

One way of doing this would be to provide a form to all potential vaccinees at the first visit to the vaccination clinic asking permission to follow up with them at a later date for a survey. A survey that could contain data from both vaccinees who chose to be vaccinated and potential vaccinees who decided against vaccination would be extremely valuable. Such a survey would be able to have a representative cohort of potential vaccinees as its study population, assuming that the nonresponse rate is similar in both populations. Being able to survey potential vaccinees who decided against receiving the vaccine will provide a representative control group (if nonresponse rates are similar) for any study of phase I vaccinees.

Another method for gathering data would be to add a carbon copy to the form that potential vaccinees complete regarding reasons for not receiving the vaccine. This method for gathering data would not offer representative cohort information (because it would not include the people who decided between the first and second visit to the vaccination clinic not to



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