This chapter describes an approach to quantifying the local inflammatory response at the injection site after a vaccination by infrared imaging. The aim is to develop a thermographic procedure providing support to evaluate the reactivity of a vaccine. The development of the experimental design had to consider an optimum timeframe for infrared imaging, the variability of the local thermal emission, questions regarding the thermal left-right symmetry and further biometric aspects. To verify this concept, more than 80 participants of the influenza vaccination campaign were involved. Even if this study is based on a well-tolerated seasonal influenza vaccination, nearly 40% of all subjects show a pronounced thermal reaction of approximately 1°C. Apart from this, 25-30% displays no signs of any thermal response. The question of how far thermal imaging will contribute to facilitating the assessment of the reactivity of a vaccine has several aspects which are discussed in this chapter.
TopIntroduction
Technical developments in high resolution Infrared Thermography provide further promising opportunities for their use in biomedical research. In this this chapter, a new thermographic application to support safety studies of vaccines is described. Vaccines are a heterogeneous class of medicinal products containing antigenic substances capable of inducing specific immunity against infective agents or toxins, or against other antigenic substances. In contrast to other biological and chemical medicinal products used for the treatment of diseases, vaccines are a preventive measure usually given to large cohorts of healthy subjects (Lopalco et.al., 2010). A high standard of safety and low reactogenicity is generally requested. For the safety evaluation, extensive clinical studies are demanded. The whole procedure remains always in the focus of public attention and is the subject of the subsequent pharmacovigilance survey (Waldman, Luhm, Monteiro, & Freitas, 2011). The outcome of clinical studies, however, may be more or less influenced by individual subjective reports about aches and pain or other discomfort. Possibly, thermal imaging provides a non-subjective approach to supplement evaluation of the vaccine reactivity here. This chapter tries to explain the steps on the way to a standardized thermographic protocol. After a suitable procedure to characterize the thermographic response after vaccination is confirmed, at least two aspects are of peculiar interest:
This is a relevant issue for statistical planning in future surveys. Furthermore, a relevant question is, whether and to what extent any relation to clinical or further attributes exists. An extracurricular vaccination program by several vaccines and each with 40 or more participants will never pass an ethical review. Thus, it was decided to join the local seasonal influenza vaccination campaign, performed regularly in Germany in each autumn. This provides the opportunity to involve a relevant number of participants and to demonstrate the feasibility of the concept under practical conditions.
A separate sub-chapter is inserted, which deals with investigations of vaccines in farm animals. These vaccines must also fulfill specific requirements of safety and must comply with standards of animal welfare. In contrast to studies in human beings, there are several different aspects. Obviously, no narrative and no subjective influence by the “vaccinee” itself is possible. However, there are quite a few critical physiological properties of the skin. Significantly, they have more thermal isolation in their skin. This is either by the fur in sheep and in cattle or by a strong subcutaneous fat layer in pigs (Eckert, 2002). Moreover, the effort in fixation of the animals to take a thermal picture cannot be underestimated. Several experiences from field studies under farm conditions were presented.
TopBackground
The biological background of this concept is based on the interaction of cellular and humoral factors in the immune reactive network, finally leading to an efficient immune response (Pichler, 2006). This is accompanied by a more or less strong local inflammatory response at the injection site. Local clinical symptoms are the mostly expected side effects and will be neglected, if not too painful. In contrast, the frequency of unexpected and severe adverse reactions after vaccination needs much more attention. These events however, are often extremely rare and can only be observed within higher numbers of vaccinated subjects or over a longer period in post marketing studies. The idea of this thermographic approach is to develop a marker to support clinical surveys to characterize the reactivity of a vaccine. It is assumed that even a slight local inflammation causes an increased local blood flow beside pain or discomfort. This leads to a more or less higher surface temperature. In contrast to the discomfort, a higher blood flow can be well quantified by metering the increase in the surface temperature of a defined area around the injection site. In doing this, a limited amount of subjects may be sufficient to provide reliable objective information about the reactivity of a vaccine and should provide data which may serve as a surrogate marker to support the evaluation of the safety profile of a vaccine.