Omicron XBB is a significant sub-variant of COVID-19 that continues to circulate globally. Understanding its characteristics is important as the virus evolves. This lineage is notable for its widespread presence and features that differentiate it from earlier forms.
Understanding Omicron XBB
Omicron XBB is a recombinant sub-variant of the Omicron strain, formed from two BA.2 sublineages (BJ.1 and BM.1.1.1). Its genetic makeup includes spike protein mutations that affect its interaction with human cells. For example, the F486P mutation increases its binding affinity to the human ACE2 receptor, aiding infection.
XBB first appeared in Singapore in 2022 and quickly spread globally, becoming a dominant sub-variant in many regions. Its rapid proliferation is attributed to mutations that enhance its ability to evade immunity from previous infections or vaccinations. XBB has shown a strong capacity to bypass existing immune responses compared to earlier Omicron sub-variants like BA.5.
Common Symptoms and Illness Severity
Infections with Omicron XBB present with mild to moderate upper respiratory symptoms, similar to previous COVID-19 strains. Common symptoms include sore throat, fatigue, fever, cough, and congestion. Individuals may also experience muscle pain, body aches, headaches, or gastrointestinal issues like nausea, vomiting, and diarrhea.
If symptoms overlap with the common cold or flu, testing for COVID-19 is advised. Omicron, including XBB, causes less severe illness than earlier variants like Alpha or Delta, with a reduced likelihood of shortness of breath or hospitalization. This is due to the virus primarily affecting the upper respiratory tract rather than the lungs, and widespread population immunity from prior infections or vaccinations.
Protection from Vaccines and Treatments
COVID-19 vaccines and updated boosters protect against Omicron XBB, primarily by preventing severe illness, hospitalization, and death. The updated 2023–2024 monovalent XBB.1.5 vaccine targets this specific lineage. Studies show these XBB.1.5-adapted vaccines offer protection against symptomatic infection. Effectiveness for preventing hospitalization ranges from 50% to 74% within 60 days of vaccination, depending on the sublineage and age group.
Antiviral treatments can reduce illness severity for individuals who contract XBB. Oral antiviral drugs like nirmatrelvir-ritonavir (Paxlovid) and molnupiravir are effective against XBB and other Omicron sub-variants. These antivirals interfere with the virus’s replication process and are recommended for high-risk patients with mild to moderate COVID-19 to reduce hospitalization or death. However, many monoclonal antibody treatments, effective against earlier strains, show diminished or no activity against XBB due to its spike protein mutations.
Recommended Public Health Measures
To mitigate the spread of Omicron XBB and protect individuals, adherence to public health measures remains important. If symptoms like sore throat, cough, or fever develop, testing for COVID-19 is recommended. A positive test result should be followed by self-isolation to prevent further transmission to others.
Wearing masks in crowded or poorly ventilated indoor settings, such as public transportation or certain restaurants, offers additional protection. For optimal protection, N95 or KN95 masks are advised. Maintaining good hand hygiene through frequent washing or sanitizing also helps reduce the risk of transmission. These actions collectively contribute to limiting the circulation of the virus in communities.