Waning protection of influenza vaccination during four influenza seasons, 2011/2012 to 2014/2015

BACKGROUND

Concerns have been raised about intraseasonal waning of the protection conferred by influenza vaccination.

METHODS

During four influenza seasons, we consecutively recruited individuals aged 18years or older who had received seasonal influenza vaccine and were subsequently admitted to the hospital for influenza infection, asassessed by reverse transcription polymerase chain reaction. We estimated the adjusted odds ratio (aOR) of influenza infection by date of vaccination, defined by tertiles, as early, intermediate or late vaccination. We used a test-negative approach with early vaccination as reference to estimate the aOR of hospital admission with influenza among late vaccinees. We conducted sensitivity analyses by means of conditional logistic regression, Cox proportional hazards regression, and using days between vaccination and hospital admission rather than vaccination date.

RESULTS

Among 3615 admitted vaccinees, 822 (23%) were positive for influenza. We observed a lower risk of influenza among late vaccinees during the 2011/2012 and 2014/2015A(H3N2)-dominant seasons: aOR=0.68 (95% CI: 0.47-1.00) and 0.69 (95% CI: 0.50-0.95). We found no differences in the risk of admission with influenza among late versus early vaccinees in the 2012/2013A(H1N1)pdm09-dominant or 2013/2014B/Yamagata lineage-dominant seasons: aOR=1.18 (95% CI: 0.58-2.41) and 0.98 (95% CI: 0.56-1.72). When we restricted our analysis to individuals aged 65years or older, we found a statistically significant lower risk of admission with influenza among late vaccinees during the 2011/2012 and 2014/2015A(H3N2)-dominant seasons: aOR=0.61 (95% CI: 0.41-0.91) and 0.69 (95% CI: 0.49-0.96). We observed 39% (95% CI: 9-59%) and 31% (95% CI: 5-50%) waning of vaccine effectiveness among participants aged 65years or older during the two A(H3N2)-dominant seasons. Similar results were obtained in the sensitivity analyses.

CONCLUSION

Waning of vaccine protection was observed among individuals aged 65years old or over in two A(H3N2)-dominant influenza seasons.

[Clinico-radiological profile of acute disseminated encephalomyelitis in the childhood population. A retrospective analysis of a series of 20 patients in a tertiary hospital]

INTRODUCTION

Acute disseminated encephalomyelitis (ADE) is an inflammatory disorder of the central nervous system that is mediated immunologically and of unknown pathogenesis. It can present at any age, but is much more frequent in children. ADE has no specific biological marker and diagnosis is based on findings from clinical and neuroimaging studies.

AIM

To enhance our knowledge of the clinico-radiological profile of this disease.

PATIENTS AND METHODS

This retrospective study involved patients under 14 years of age who were admitted to a tertiary hospital over the last 15 years with a diagnosis of ADE. History, clinical presenting symptoms, lab findings from blood/cerebrospinal fluid analyses and radiological semiology were reviewed. In 16 cases an average follow-up of 25 months was performed.

RESULTS

The study examined 20 patients, 70% children, with a mean age of 4.4 years. Forty per cent had a previous febrile episode. Eighty-five per cent presented fever or vomiting, and 70% had altered states of mind. Motor deficits (45%), convulsions (35%) and involvement of the cranial nerves (30%) were predominant. Three children progressed with relapses and three others were left with motor sequelae. Magnetic resonance imaging showed hyperintense lesions in T2, with a pattern of scarce/no enhancement, which were predominantly located in the thalamus (70%), the spinal cord (67%) and the white matter of the sub-cortex (50%). Haemorrhagic ADE was diagnosed in two patients.

CONCLUSIONS

ADE is a condition with an important degree of general involvement and neurological repercussions, as well as considerable potential to leave the patient with sequelae. Clinico-analytical data and magnetic resonance scans of the head and spinal cord are relevant for the initial diagnosis and follow-up of patients with ADE.