Abstract
ObjectivesTo examine the risk of adverse effects of special interest in persons vaccinated against seasonal influenza compared with unvaccinated persons aged 65 and above.MethodsWe retrospectively observed 41,986 vaccinated elderly persons and 50,973 unvaccinated elderly persons in Taiwan from October 1, 2008, through September 30, 2009, using the National Health Insurance database. Neurological and autoimmune disorders and one-year hospitalization rates and in-hospital mortality rates were analyzed according to the vaccination status. Propensity score analysis was used to assess the relationship between adverse outcomes, hospitalization rates, and vaccination status.Results45% of the elderly received influenza vaccination. Multiple logistic regression showed that the probability of being vaccinated was related to more patients visiting for URI symptoms (odds ratio (OR), 1.03; 95% CI, 1.02–1.03), men (OR, 1.15; 95% CI, 1.12–1.17), increased age (OR, 1.02; 95% CI, 1.02–1.03), and more comorbidities (OR, 1.2; 95% CI, 1.17–1.23). There were no statistical differences in neurological and autoimmune diseases between the vaccinated and unvaccinated individuals using propensity score analysis, but vaccinated persons had a reduced hospitalization rate of 19% (odds ratio [OR], 0.81; 95% CI, 0.77–0.84) for the first six-months and 13% for one-year of follow-up (OR, 0.87; 95% CI, 0.85–0.9).ConclusionsBased on data from the one-year follow-ups among 93,049 elderly persons in Taiwan, reassuring results for selected neurological and autoimmune diseases were found among the vaccinated individuals after adjusting other factors. Influenza vaccination decreased the risk for hospitalization. Public health strategies must continue to improve the influenza vaccination rate among the elderly with information based upon tangible evidence.
Highlights
Influenza, which typically occurs during the late fall through early spring in the United States, is associated with high rates of morbidity and mortality, especially for the elderly [1]
The protective effect of influenza vaccinations have been proven, concern about influenza vaccination safety is often cited by the mass media or persons who decline to undergo vaccination
Bell’s palsy, GuillainBarre syndrome (GBS), pericarditis, and nephritic syndrome have been noted in individuals with influenza vaccination in case reports [6,7,8]
Summary
Influenza, which typically occurs during the late fall through early spring in the United States, is associated with high rates of morbidity and mortality, especially for the elderly [1]. Several neurological disorders have been reported to be associated with influenza vaccinations. Bell’s palsy, GuillainBarre syndrome (GBS), pericarditis, and nephritic syndrome have been noted in individuals with influenza vaccination in case reports [6,7,8]. This is especially important for GBS, a relatively rare condition that was causally linked to the 1976 swine-influenza A (H1N1) vaccination campaign in the United States [9]. A recent study revealed mild increased risk for Bell’s palsy, paraesthesia, and inflammatory bowel disease was noted in individuals with H1N1 influenza vaccinations in Sweden [13]. In order to achieve higher influenza vaccination coverage for persons aged 65 years or above, adverse events risk evaluation and new strategies may be needed [14]
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