Covid-19 pneumonia... before or after vaccination?
67-years-old male patient with fever (37.5°, peak of 39° in the past days), dry cough , dyspnea and moderate oxygen desaturation. Vaccinated 10 days before (first dose mRna Sars-Cov-2 vaccine). Co-morbidities: Hypertension. Positive Rt-PCR test for Sars-Cov-2.
Chest-CT shows some pseudonodular "ground glass" parenchymal opacities (as inflammatory processes in the acute phase), located bilaterally mainly in the subpleural lung portions, some of which with partial extension in the central portions. Some of these opacities also have smooth thickening of the underlying interlobular septa, giving a "crazy-paving" appearance. Other opacities show tendency to consolidation (intermediate phase), localized in the right upper lobe posterior segment and in both lower lobes. In the lower lobes posterior segments there are fibrotic-like bands (striplike opacities). The aforementioned findings refer to viral inflammatory processes of moderate degree, with temporal variability of onset ("asynchronous" lesions).
Kanne et al. divided Covid-19 imaging pattern into three phases of evolution of the disease: early (0-4 days from the onset of symptoms), middle (5-13 days) and late-stage (over 14 days). Generally, the early phase is characterized by isolated ground-glass opacities (GGO) (also in multiple and sparse form), expression of the compromise of the intra-lobular interstitium that thickens with edema and the alveoli fill with exudate. In the GGO, the content of intra-alveolar air undergoes only a partial reduction. With the extension of diffuse alveolar damage (DAD), these lesions tend subsequently to confluence in areas of greater extension, typically in the peripheral portions of the lung parenchyma (especially in the posterior sectors). Secondly, crazy paving pattern appears, ie the presence of GGO with superimposed interlobular septal thickening. The intermediate phase is the organizing-proliferative one: pneumocytes type II, fibroblasts and myofibroblasts proliferate. These migrate from the interstitium and transform the intra-alveolar exudate (fluid) into granulation tissue (compact). In this phase, parenchymal consolidations often appear. Therefore, there is an evolution towards organizing pneumonia. In the late-stage, striplike opacities appear: they are curvilinear radiopaque bands, generally formed by replacing the parenchymal consolidations. Striplike opacities are accounted as a sign of improvement of the lung picture (benign evolution or “dissipation stage”), as they could represent residual fibrous bands, both interstitial and intralobular, generated by the activation of fibroblasts and collagen hyperproduction.
Assuming that there are often atypical, indeterminate and negative pulmonary appearence of the disease, the finding of determinate CT signs allows to guess the state and the course of Covid-19 pneumonia. CT could also predict the date of onset of the alleged contagion: in our case, findings of striplike opacities could refer it 4-5 days before vaccination. Covid-19 pneumonia is strictly time-dependent. Coexistence of different patterns is a demonstration of the temporal asynchrony of the viral pneumonia.