New chest CT study assesses impact of COVID-19 variants and vaccination status

Typical computed tomography (CT) findings for COVID-19 would be less likely for people with the omicron variant of the disease compared to those with the delta variant, and giving multiple doses of vaccination reduces the odds. of typical CT findings and elevated CT severity scores in people with COVID-19, according to a recently published multicenter study.

For the retrospective study, recently published in Radiology, researchers in France reviewed the CT exams of 3,876 patients (median age 68) who presented to 93 emergency departments with COVID-19 between July 2021 and March 2022.

To assess the impact and reflect the peak periods of the omicron and delta variants of COVID-19, the study authors characterized CT scans performed before November 15, 2021 as “delta-predominant” (1,080 patients , 28%); CT examinations performed between November 15 and December 31, 2021 as a “transition” (790 patients, 20%); and CT scans performed after January 1, 2022 as “omicron-predominant” (1,629 patients, 42%).

The study authors found that the proportion of typical chest CT findings for COVID-19, ranging from ground-glass opacities and consolidations to fibrotic bands and reticulations, was 32% higher in unvaccinated patients ( 76%) compared to patients who had at least one vaccination dose (44 percent). According to the study, 43% of unvaccinated patients had a high CT severity score, compared to 25% of vaccinated patients.

“Regardless of time period, vaccination was associated with diagnostic and severity scores…with less extent of disease and lower frequency of typical patterns in vaccinated patients,” the co-author wrote. study Guillaume Gorincour, MD, affiliated with Imadis Teleradiology in Lyon, France, and colleagues.

(Editor’s note: For related content, see “How accurate is the CT Severity Score in predicting the severity of COVID-19?,” “CT study reveals persistent lung abnormalities two years after COVID-19” And “Study shows merits of photon-counting computed tomography in detecting subtle lung abnormalities post-COVID. »

The researchers found that the proportion of the aforementioned typical chest CT findings for COVID-19, during the omicron-predominant period, was 25% lower (49%) compared to the delta-predominant period (74%). The proportion of high CT severity scores was 10% lower (29%) in the omicron-predominant period compared to the delta-predominant period (39%).

“Radiologists should be aware of the influence of vaccination and new variants on CT scan results and adapt their interpretations and conclusions accordingly, especially as full vaccination coverage increases and new subvariants of omicron can re-infect previously immunized individuals,” argued Gorincour and colleagues.

According to the study, a multivariate analysis revealed that one vaccine dose was not significantly associated with a reduced likelihood of typical chest CT patterns and severity scores compared to unvaccinated patients. However, Gorincour and colleagues noted that patients who received two doses of vaccination and three doses of vaccination had lower odds ratios (ORs) for typical COVID-19 chest CT scan findings (32% and 20% respectively). and high CT severity scores (47% and 33% respectively) compared to unvaccinated patients.

Regarding study limitations, the authors acknowledged possible bias due to subjective assessment of CT scan severity scores during on-call duty in the emergency department and knowledge of vaccination status. of the patient by RT-PCR and COVID-19 before radiological evaluation of chest CT scans. Gorincour and colleagues also noted that bronchial wall thickening and peribronchovascular predilection, more commonly reported with the omicron variant, were not assessed in this study.