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Vaccination and the Omicron Variant - The Effect on Chest CT Findings

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The omicron variant of COVID-19 and vaccination may have visible effects on the lungs and the chest CT scan findings. Read below to learn more about it.

Medically reviewed by

Dr. Arpit Varshney

Published At May 2, 2023
Reviewed AtJanuary 12, 2024


The COVID-19 pandemic was caused by a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) discovered in China in late 2019. Variant strains have emerged from this strain, B.1.617.2 (delta) and B.1.1.529 (omicron) being the most recent variant. Coronavirus disease (COVID-19) is an infectious viral disease. Most of the people who get infected experience mild to moderate respiratory illness and recover without specific treatment. However, some people become seriously ill and require medical attention. Older people and people with comorbidities (underlying medical conditions such as diabetes, cardiovascular disease, chronic respiratory disease, and cancer) are more likely to develop serious illnesses. Anyone can catch COVID-19 and become seriously ill or die at any age.

What Is the COVID-19 Omicron Variant?

The COVID-19 virus constantly evolves as it tries to evade human immune responses and infect more people, but most of that evolution is trivial. Occasionally, variants of the disease emerge and should be investigated. Omicron is the latest development, followed by Delta, Gamma, Beta, and Alpha variations. A South African epidemiologist sequenced the Omicron strain and reported the results to the World Health Organization (WHO). They found that the viral spike protein contains more than 30 mutations. This allows the virus to enter and infect cells. The subspecies was first discovered in Botswana, but experts say its origin is still unknown and will likely circulate for even longer.

What Is a CT Scan?

A computed tomography (CT) scan combines a series of X-ray images taken from various angles around the body and uses computer processing to create cross-sectional images (slices) of bones, blood vessels, and soft tissues inside the body. A CT scan image provides more detailed information than a simple X-ray. CT scans have many uses, but they are particularly well-suited for quickly examining people with possible internal injuries from car accidents or other types of trauma. CT scans can be used to view almost any part of the body, diagnose disease or injury, and plan medical, surgical, or radiation therapy.

How Do Vaccinations Help With Preventing COVID-19 Infections?

The COVID-19 vaccine prepares the immune system to protect against COVID-19. These vaccines are important tools to stop the COVID-19 pandemic. Everyone over the age of six months should be vaccinated against COVID-19. This includes pregnant women and women planning a pregnancy. Even if a person has already had COVID-19, they should get vaccinated. The COVID-19 vaccine protects people from contracting COVID-19 or more severe symptoms. These vaccines teach the body to protect itself from the SARS-CoV-2 virus that causes COVID-19. The COVID-19 vaccine is very effective for:

  • Preventing transmission of the SARS-CoV-2 virus that causes COVID-19.

  • Protection against hospitalization, severe illness, and death from COVID-19.

  • Reducing the risk of people spreading COVID-19.

What Is the Role of a Chest CT in COVID-19 Infections?

A CT scan is used as a follow-up tool to monitor the coronavirus disease progression and assess the severity of COVID-19 patients in terms of the extent of lung involvement. In addition, CT can predict prognosis (course of the disease). Image appearance of bilateral lung lesions is considered an additional indicator and represents the highest value for lymphopenia (lack of lymphocytes in white blood cells), bacterial co-infection, smoking history, hypertension (high blood pressure), and age. It can also predict mortality in COVID-19 patients compared to other viral pneumonia (lung infection caused by the virus).

What Does COVID Infection Look Like on a CT Scan?

A lung computed tomography (CT) scan of a COVID-19 (SARS-CoV-2) positive patient shows the following findings:

  • White Ground Glass Opacities (GGO) - They are caused by COVID pneumonia. Pneumonia usually develops along the walls of each lung lobe, especially the chest wall and the lower portion of the lung. As the name suggests, ground-glass opacity looks like ground-glass spread over the lungs. Gray areas do not appear transparent; they appear opaque instead. They are also present on both lungs indicating the appearance of multiple gray patches on the inner or outer surface of the lung. They are very commonly seen in computed tomography scans of COVID-19 patients.

  • Crazy Paving - It occurs in straight lines on an opaque background of frosted glass, giving an irregular appearance. Crazy paving appearing on computed tomography scans often indicates the progression or worsening of COVID-19 disease. It is because of fluid accumulation that leads to the formation of these crazy patch patterns.

  • Vascular Dilation - A computed tomography scan may show dilation of blood vessels or vasodilatation. Vasodilation is usually seen in ground-glass opaque areas. This plays an important role in hypoxemia (low oxygen levels in blood) in COVID-19 patients.

  • Consolidation​ - It forms when fluid fills the airways present in the lungs. It forms in multiple patterns and occurs in different areas of the lung. It also shows the progress of COVID-19.

  • Reticular Pattern - It appears like a net and is a compilation of tiny linear opacities. They are generated when the interstitial structures thicken. Consequently, it hinders the filling of air in the air sacs and causes difficulty breathing. Reticular patterns increase mainly in prolonged COVID-19 cases.

  • Traction Bronchiectasis - Traction bronchiectasis can cause bronchial tissue dilation and inflammation. The bronchi become thickened, making breathing difficult and expelling phlegm and mucus difficult.

What Is the Impact of Vaccination and the Omicron Variant on COVID-19-Related Chest CT Findings?

According to researchers, two vaccine doses significantly protect computed tomography scans in case of severe COVID-19. The incidence and severity of pneumonia were lower in patients who developed a breakthrough infection in patients fully vaccinated with mRNA (messenger ribonucleic acid) and adenoviral vector vaccines compared with unvaccinated patients. Also, pulmonary infiltration visibility on lung computed tomography scans is rare in patients infected with the omicron variant, as the omicron variant was restricted to the upper respiratory tract and affected the lungs less.


A computed tomography scan provides a complete representation of the lungs. Doctors can analyze computed tomography scans to determine patient status and better treat patients with COVID-19. Affected lung areas appear as white or gray patches on computed tomography scans. These spots can be of various shapes and scattered throughout the lungs. A doctor examines the computed tomography (CT) images and develops a treatment plan for the patient's benefit.

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Dr. Arpit Varshney
Dr. Arpit Varshney

General Medicine


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