Hospitalization following influenza infection and pandemic vaccination in multiple sclerosis patients: a nationwide population-based registry study from Norway

Abstract

Patients with multiple sclerosis (MS) are at increased risk of infections and related worsening of neurological function. Influenza infection has been associated with increased risk of various neurological complications. We conducted a populationbased registry study to investigate the risk of acute hospitalization of MS patients in relation to influenza infection or pandemic vaccination in Norway. The entire Norwegian population in the years 2008-2014 was defined as our study population (N = 5,219,296). Information on MS diagnosis, influenza infection and vaccination were provided by Norwegian national registries. The self-controlled case series method was used to estimate incidence rate ratios (IRRs) with 95% confidence intervals (95% CI) in defined risk periods. 6755 MS patients were identified during the study period. Average age at first registration of an MS diagnosis was 51.8 years among men and 49.9 years among females (66.9%). The IRR for emergency hospitalization among MS patients the first week after an influenza diagnosis was 3.4 (95% CI 2.4-4.8). The IRR was 5.6 (95% CI 2.7-11.3) after pandemic influenza, and 4.8 (95% CI 3.1-7.4) after seasonal influenza. Pandemic vaccination did not influence risk of hospitalization [IRR within the first week: 0.7 (95% CI 0.5-1.0)]. Among MS patients, influenza infection was associated with increased risk for acute hospitalization while no increased risk was observed after pandemic vaccination. Influenza vaccination could prevent worsening of MS-related symptoms as well as risk of hospitalization.

COVID-19 and disease-modifying therapies in patients with demyelinating diseases of the central nervous system: A systematic review

“…The risk of infection during epidemics in these patients has been studied before. For example, Ghaderi S et al ( Ghaderi et al, 2020 ) reported that influenza infection is associated with an increased risk for acute hospitalization, and vaccination could prevent this risk among MS patients. ( Ghaderi et al, 2020 ) Several studies have already reported on SARS-CoV-2 infection in patients with MS and NMOSD and have evaluated the relation COVID-19 course with different DMTs ( Table 1 , 2 ).…”

“…For example, Ghaderi S et al ( Ghaderi et al, 2020 ) reported that influenza infection is associated with an increased risk for acute hospitalization, and vaccination could prevent this risk among MS patients. ( Ghaderi et al, 2020 ) Several studies have already reported on SARS-CoV-2 infection in patients with MS and NMOSD and have evaluated the relation COVID-19 course with different DMTs ( Table 1 , 2 ). Although limited by a small sample size and multiple possible sources of bias, these papers provide essential information to understand the risk of infection in patients on different medications.…”

Current Immunological and Clinical Perspective on Vaccinations in Multiple Sclerosis Patients: Are They Safe after All?

“…Multiple studies regarding two prevalent inactivated vaccines (FOCETRIA—seasonal [ 55 ]; PANDEMRIX—pandemic [ 56 ]) revealed two common findings: (1) An increased risk of acute hospitalization that correlates with exacerbations among MS patients was noted with the onset around the time of clinical influenza infection. (2) No additional risk of acute hospitalizations following neither the pandemic or seasonal influenza vaccinations was identified among MS patients [ 57 , 58 ].…”

Assessing the consistency and validity of self-reported year of diagnosis among participants in a longitudinal study of people with multiple sclerosis

“…The risk of infection during epidemics in these patients has been studied before. For example, Ghaderi S et al (2020) reported that influenza infection is associated with an increased risk for acute hospitalization, and vaccination could prevent this risk among MS patients. Ghaderi et al (2020) Several studies have already reported on SARS-CoV-2 infection in patients with MS and NMOSD and have evaluated the relation COVID-19 course with different DMTs (Tables 1 and 2).…”

“…For example, Ghaderi S et al (2020) reported that influenza infection is associated with an increased risk for acute hospitalization, and vaccination could prevent this risk among MS patients. Ghaderi et al (2020) Several studies have already reported on SARS-CoV-2 infection in patients with MS and NMOSD and have evaluated the relation COVID-19 course with different DMTs (Tables 1 and 2). Although limited by a small sample size and multiple possible sources of bias, these papers provide essential information to understand the risk of infection in patients on different medications.…”