【Omicron Variant】Omicron - What We Know So Far
The possible 5th wave of COVID-19 has raised an alarming concern over the transmission rate of Omicron variant and effectiveness of COVID-19 vaccines against Omicron. Below information summarises what you ought to know about this disturbing variant:
1. When and where did Omicron start?
The SARS-CoV-2 variant Omicron (B.1.1.529) was first reported to WHO from South Africa on Nov 23 2021, and was later designated as a Variant of Concern (VOC) in Nov 26 2021. Omicron cases have been detected in more than 95 countries or regions by now1。
2. What are the symptoms of Omicron?
Symptoms of Omicron and other COVID-19 variants are quite similar, while the top five Omicron symptoms reported were2：
- Runny nose
- Fatigue (either mild or severe)
- Sore throat
3. Is Omicron more contagious?
Earlier evidence indicated that Omicron is two to four times as likely to spread as Delta (Omicron cases are doubling every two to four days)3. A study from HKUMed found that Omicron infects and multiplies 70 times faster than Delta and original SARS-CoV-2 in human bronchus, meaning it is easier to infect the cells of upper airways (including the nose, throat and trachea), which is believed to be one of the reasons of Omicron’s higher transmission rate4。
4. Does Omicron cause a less severe illness?
According to early Omicron cases, Omicron hospitalisation risk around one third of Delta and its symptoms are usually less severe５. It is found that Omicron replicated less efficiently (more than 10 times slower) in the human lung tissue than other variants, which may cause lower severity of illness4。
5. Are COVID-19 vaccines effective against Omicron?
It is believed that receiving the third shot is more effective against Omicron; whereas the protection from two doses of vaccine may not be as significant as to other variants . However, apart from simply triggering antibodies production against viruses, COVID-19 vaccines also stimulate the growth of T cells which can slower virus infection which in turns causing a less severe disease6. However, different immune responses and types of vaccine affect the amount of effective antibodies produced after vaccination. If the amount of effective antibodies triggered after vaccination is low, there is still a high chance of infection.
6. What should I protect myself from Omicron?
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1 Omicron：到目前為止我們所瞭解的資訊 (Health Matters, 2021)
2 Omicron and cold-like symptoms rapidly taking over in London (Zoe COVID Study, 2021)
3 Omicron: What We Know About the New Coronavirus Variant (New York Times, 2022)
4 港大醫學院研究發現新型冠狀病毒變異株OMICRON較DELTA更容易感染人類支氣管 但於肺部感染較弱 (港大醫學院, 2021)
5 Omicron hospitalisation risk around one third of Delta, UK analysis shows (Reuters, 2022)
6 Omicron is less severe because it does not infiltrate the lungs (Aljazeera, 2022)