Dataset Information

Encephalitis after influenza and vaccination: a nationwide population-based registry study from Norway.

ABSTRACT:

Background

Influenza is known to be associated with various neurological complications, including encephalitis. We conducted a registry-based study to assess the risk of encephalitis after influenza and A(H1N1)pdm09 vaccine.

Methods

Data from Norwegian national health registries during 2008-14 were linked using the unique personal identifiers given to all Norwegian residents (N = 5 210 519). Cox proportional-hazard models with time-varying variables were fitted to estimate hazard ratios (HRs) of encephalitis after influenza and A(H1N1)pdm09 vaccine, using the risk windows 0-7, 0-14, 0-30, 0-60, 0-90 and 0-180 days.

Results

In Norway, 684 172 individuals received an influenza diagnosis and 2793 patients were hospitalized with encephalitis during 2008-14. The risk of encephalitis increased after influenza: HR, 7-day risk window: 47.8 (95% confidence interval (CI): 35.8-63.8), and the HR decreased for longer risk windows; HR, 180-day risk window: 3.8 (95% CI: 3.1-4.7). HR of encephalitis after influenza during the 2009 main pandemic wave using a 7-day risk window was 30.0 (95% CI: 10.8-83.2). We found no differences in the risk of encephalitis after the seasonal influenza compared with influenza during the 2009 main pandemic wave; HR, 7-day risk window: 1.3 (95% CI: 0.4-4.3). A(H1N1)pdm09 vaccine was not associated with the risk of encephalitis: HR, 14-day risk window: 0.6 (95% CI: 0.2-2.1).

Conclusions

There was an increased risk of encephalitis following influenza but not after A(H1N1)pdm09 vaccine. The risk of encephalitis was highest in the first few weeks after influenza.

SUBMITTER: Ghaderi S

PROVIDER: S-EPMC7313985 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:PurposeLower COVID-19 vaccination rates have been observed among some adult immigrant populations in Norway, and there appears to be an association with sociodemographic factors. However, knowledge is lacking on the distribution of vaccination rates and role of sociodemographic factors among adolescents. This study aims to describe COVID-19 vaccination rates among adolescents according to immigrant background, household income, and parental education.MethodsIn this nationwide registry study, we analyzed individual-level data on adolescents (12-17 years) from the Norwegian Emergency preparedness register for COVID-19 until September 15th, 2022. We estimated incidence rate ratios (IRR) for receiving at least one COVID-19 vaccine dose by country background, household income and parental education, using Poisson regression, adjusting for age, sex, and county.ResultsThe sample comprised 384,815 adolescents. Foreign-born and Norwegian-born with foreign-born parents, had lower vaccination rates (57 % and 58 %) compared to adolescents with at least one Norwegian-born parent (84 %). Vaccination rates by country background varied from 88 % (Vietnam) to 31 % (Russia). Variation and associations by country background, household income, and parental education were greater among 12-15-year-olds than 16-17-year-olds. Household income and parental education were positively associated with vaccination. Compared to the lowest income and education category, IRRs for household income ranged from 1.07 (95 % CI 1.06-1.09) to 1.31 (95 % CI 1.29-1.33) among 12-15-year-olds, and 1.06 (95 % CI 1.04-1.07) to 1.17 (95 % CI 1.15-1.18) among 16-17-year-olds. For parental education, from IRR 1.08 (95 % CI 1.06-1.09) to 1.18 (95 % CI 1.17-1.20) among 12-15-year-olds, and 1.05 (95 % CI 1.04-1.07) to 1.09 (95 % CI 1.07-1.10) among 16-17-year-olds.ConclusionCOVID-19 vaccination rates varied by immigrant background and age group, with lower rates especially among adolescents with background from Eastern Europe and among younger adolescents. Household income and parental education were positively associated with vaccination rates. Our results may help target measures to increase vaccination rates among adolescents.