Literature Review on Individuals with Neurologic or Neurodevelopment Conditions and Risk of Serious Influenza-Related Complications

Neurologic or neurodevelopment conditions (NNCs) account for a substantial burden of disease globally and in Canada. Based on preliminary reviews of evidence, NACI has included children (since the 2015−2016 influenza season) and adults (since the 2016−2017 influenza season) with NNCs among the high-risk groups for whom influenza vaccination is particularly recommended. The present literature review was conducted to provide a rapid synthesis of the evidence to further inform NACI’s assessment regarding the inclusion of individuals with NNCs as a high-risk group for influenza-related complications. Although a large number of studies were identified, the body of evidence related to the risk of serious influenza-related complications in adults and children with NNCs is mostly comprised of descriptive studies (i.e., case series), which are generally considered of lower quality (level III evidence). There was also a lack of clarity in the composition of conditions constituting NNCs in some studies and a lack of consistency across identified studies in the defined lists of specific NNCs investigated. However, the body of evidence appears to suggest consistency in the burden and direction of risk of NNCs in both adults and children for pandemic influenza A(H1N1)pdm09 and seasonal influenza. Overall, studies suggest a relatively high burden of pre-existing NNCs in children and adults who had experienced serious pandemic influenza A(H1N1)pdm09- and seasonal influenza-related complications, such as hospitalization, intensive care unit admission and death. There is also consistent evidence to suggest that pre-existing NNCs increase the risk for these serious influenza-related complications. Limited evidence was identified for influenza-related emergency department presentation, respiratory failure and need for mechanical ventilation. The findings of the present rapid literature review are consistent with the preliminary evidence supporting children and adults with NNCs as groups at risk for influenza-related complications and hospitalization.