All scans were acquired 3 h after receiving the vaccine/placebo on a GE, 3T Signa Excite
HD system (Milwaukee, USA) with a 32-channel head coil. A structural T1 scan (repetition
time = 2300 ms, echo time = 2.96 ms, 192 sagittal slices, 1 mm3 isotropic
voxels and image resolution 256 × 256) was obtained for co-registration purposes. A
resting-state fMRI scan (10 min; eyes open) was acquired with single-shot full k-space
echo-planar imaging with ramp sampling correction using the intercommissural line (AC–PC)
as a reference (repetition time = 2000 ms, echo time = 29 ms, matrix size = 64 × 64, 32
slices, voxel size = 3 × 3 × 4 mm3, axial plane – series ascending –
multi-slice mode; interleaved; 300 volumes). Preprocessing was carried out using
Statistical Parametric Mapping software (SPM12; Wellcome Department of Cognitive
Neurology, London, UK). Briefly, this included the removal of the first five volumes,
manual reorientation, T1 co-registration to functional scans, segmentation and
normalisation by DARTEL, and spatial smoothing (6 mm full width at half maximum), and
band-pass filters (0.01–0.09 Hz). To correct for head movement, 24 motion parameters (6
head motion parameters, 6 head motion parameters one time point before, and the 12
corresponding squared items), along with signals from the white matter and CSF were
regressed for each subject and session at the voxel level.
HD system (Milwaukee, USA) with a 32-channel head coil. A structural T1 scan (repetition
time = 2300 ms, echo time = 2.96 ms, 192 sagittal slices, 1 mm3 isotropic
voxels and image resolution 256 × 256) was obtained for co-registration purposes. A
resting-state fMRI scan (10 min; eyes open) was acquired with single-shot full k-space
echo-planar imaging with ramp sampling correction using the intercommissural line (AC–PC)
as a reference (repetition time = 2000 ms, echo time = 29 ms, matrix size = 64 × 64, 32
slices, voxel size = 3 × 3 × 4 mm3, axial plane – series ascending –
multi-slice mode; interleaved; 300 volumes). Preprocessing was carried out using
Statistical Parametric Mapping software (SPM12; Wellcome Department of Cognitive
Neurology, London, UK). Briefly, this included the removal of the first five volumes,
manual reorientation, T1 co-registration to functional scans, segmentation and
normalisation by DARTEL, and spatial smoothing (6 mm full width at half maximum), and
band-pass filters (0.01–0.09 Hz). To correct for head movement, 24 motion parameters (6
head motion parameters, 6 head motion parameters one time point before, and the 12
corresponding squared items), along with signals from the white matter and CSF were
regressed for each subject and session at the voxel level.