Conclusion 9.1: The evidence is inadequate to accept or reject a causal relationship between HPV vaccine and ADEM.
No studies were identified in the literature for the committee to evaluate the risk of transverse myelitis 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 transverse myelitis.
The committee identified two publications reporting the development of transverse myelitis after administration of HPV vaccine. The publications did not provide evidence beyond temporality (Borja-Hart et al., 2009; Slade 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 transverse myelitis. Autoantibodies, T cells, and molecular mimicry may contribute to the symptoms of transverse myelitis; 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 transverse myelitis as lacking.
Conclusion 9.2: The evidence is inadequate to accept or reject a causal relationship between HPV vaccine and transverse myelitis.