inoculations with the second and third dose administered 2 and 6 months after the first dose (CDC, 2010a). Both vaccines protect against 70 percent of HPV16 and 18 associated cancers, with Gardasil providing additional protection against 80 to 90 percent of genital wart–causing HPV infections (Bonnez and Reichman, 2010; CDC, 2010a). In 2009, 44.3 percent of girls in the United States aged 13 to 17 had received at least an initial dose of either the HPV4 or HPV2 vaccine (CDC, 2010c).
No studies were identified in the literature for the committee to evaluate the risk of acute disseminated encephalomyelitis (ADEM) after the administration of HPV vaccine.
Weight of Epidemiologic Evidence
The epidemiologic evidence is insufficient or absent to assess an association between HPV vaccine and ADEM.
The committee identified four publications reporting ADEM after administration of HPV vaccine. The publications did not provide evidence beyond temporality (Borja-Hart et al., 2009; Mendoza Plasencia et al., 2010; Schaffer et al., 2008; Wildemann et al., 2009). In addition, Borja-Hart et al. (2009) intimated that in some cases multiple vaccines were administered concomitantly, making it difficult to determine which, if any, vaccine could have been the precipitating event. The publications did not contribute to the weight of mechanistic evidence.
Weight of Mechanistic Evidence
The symptoms described in the publications referenced above are consistent with those leading to a diagnosis of ADEM. Autoantibodies, T cells, and molecular mimicry may contribute to the symptoms of ADEM; however, the publications did not provide evidence linking these mechanisms to HPV vaccine.
The committee assesses the mechanistic evidence regarding an association between HPV vaccine and ADEM as lacking.