Predicting vaccination using numerical and affective risk perceptions: the case of A/H1N1 influenza.

During the 2009 A/H1N1 flu pandemic, German health authorities recommended vaccination; however, the efficacy of such programs largely depends on individuals' risk perception. Risk perceptions are commonly determined through numerical-cognitive estimates such as the perceived likelihood and severity of the hazard. Instead, we argue that risk perceptions, which include more affect-related aspects such as worry and threat, are more powerful predictors of protective behaviors. Moreover, vaccines are often perceived as double-edged since they offer protection but also involve adverse side-effects. As such, in the context of the A/H1N1 vaccine uptake, risk perception is not only disease-related (A/H1N1 infection) but also vaccine-related (A/H1N1 vaccine). The present longitudinal study was conducted during the run-up to the German A/H1N1 vaccination campaign and measured cognitive and affective risk perceptions associated with both the A/H1N1 infection and its vaccine (T1, October 2009, N=397) in order to assess their impact on (self-reported) A/H1N1 vaccination eight weeks later (T2, December 2009; N=285). As assumed, greater perceived likelihood and severity of infection were associated with greater affective risk perception at T1. The more threatened and worried people felt, the more they intended to get vaccinated; however, the greater the perceived likelihood and severity of vaccine adverse side-effects, the greater the amount of vaccine related affective risk perception, impeding vaccination intention. Finally, vaccination intention predicted vaccination eight weeks later at T2 (OR=2.2). The results suggest that numerical-cognitive risk perceptions, which are typically the target of public vaccination campaigns, do not impact preventive intention directly; instead, they facilitate affect-related risk perceptions, which motivate protective action.