What is Omicron (B.1.1.529)?
Omicron (B.1.1.529) is a variant of SARS-CoV-2 that has been identified initially in COVID-19 patients in Botswana and South Africa. The WHO Technical Advisory Group on Virus Evolution (TAG-VE) felt that this virus had too many mutations and may be easily spread globally causing a spike in COVID cases worldwide. Hence, TAG-VE labelled it a Variant of Concern(VOC). Delta is the other variants that has been previously labelled as VOC.
According to the WHO, 77 countries across the world have now reported cases of Omicron, in fact it probably is present in most countries even if it has not been detected yet. In India, 101 cases of omicron have been reported. It is spreading at a rate not seen with any other variant and people may be dismissing it thinking it causes a less severe disease but the sheer number of cases can overburden the health system. WHO advises that vaccine alone will not help countries out of this crisis. We must stop the spread! It's not vaccines against masks, social distancing, ventilation or hand hygiene. We need to Do It All and Do It Consistently!
What is a Variant of Concern (VOC)?
While the viruses multiply, all varieties of viruses included SARS-CoV-2 acquire mutations in their genetic material or genome. This virus has mutated into multiple variants during the pandemic. The scientists keep collecting data on the different variants from all over the globe by studying their genetic sequence in laboratories to see the contagiousness and disease severity caused by these variants. So these variants have one common ancestor or lineage which started the pandemic in Wuhan but over the past two years the characteristics of the virus have changed especially in variants with too many mutations. Greek alphabets have been used to label the variants. These have implications as far as diagnosis, treatment, vaccination and control strategies are concerned.
The SARS-CoV-2 variants are classified as :
- Variants Being Monitored (VBM) (eg. Alpha, Beta, Gamma)-not a significant threat to public at present and are circulating at low levels.
- Variant Of Interest (VOI)(no variant at present)-has specific attributes including changes in the receptor binding, transmission, potential pf increase in clusters of cases.
- Variant Of Concern (VOC)(eg. Delta, Omicron)-increased transmission or more severe disease
- Variant Of High Consequence (VOHC) (no variant at present)-failure to be detected by current diagnostic tests and significantly reduced susceptibility to treatment and vaccines, more severe disease.
The variant status can be escalated or deescalated by the WHO basis the data gathered on the behaviour of the variant. Alpha, Beta and Gamma were VOC in Dec 2020 but later changed to VBM in Sept 2021. Delta variant was first identified in India.
Why has Omicron been labelled as a Variant of Concern?
Omicron has been called a VOC since it has multiple mutations and substitutions in the spike protein and has replaced the Delta variant in South Africa. Not only this, it has been detected in multiple countries around the globe even in patients who did not have a travel history. It maybe less susceptible to the vaccine induced protection and treatments including monoclonal antibodies currently available. Scientists are still gathering evidence regarding disease transmissibility and severity of Omicron.
What are the concerns regarding Omicron?
There are unanswered questions regarding the contagiousness or transmissibility of Omicron compared to the existing variants. Epidemiologists are analysing data in South Africa and other nations of the world to solve this mystery. Data is also being gathered in United Kingdom and other European countries where the Omicron cases now outnumber those in S.Africa.
The second and more pertinent question is with regards to the severity of illness caused by Omicron. Preliminary information shows that the virus is affecting younger individuals but resulting in milder disease. The symptoms are very similar to those produced by other variants. A much clearer picture will emerge in the next few months. We still need to be extremely cautious since all COVID-19 variants can result in serious disease and fatality in susceptible persons, especially those with co-morbidities.
A third concern is the increased risk of re-infection with Omicron in people who have already had COVID-19 infection or breakthrough infections in those who are vaccinated but we are awaiting further information on this aspect. With so many Indians having had the disease and more than half of our population having been vaccinated, are we at a potential advantage compared to other nations is debatable.
Fourthly, vaccines have been the promised ray of hope for fighting the epidemic. WHO, scientists and the pharmaceutical partners are testing on a war-footing to analyse whether the current vaccines are effective against this variant or will we need to modify the vaccines to stay protected against this virus. We are getting some preliminary data with variable results with vaccines from Pfizer and Astra Zeneca/Covishield. At the same time the antibodies levels from the previously administered two doses are fast dwindling and the controversy remains regarding vaccine mixing for the booster shots. One thing that is certain is that we do need booster shots but the million dollar question is, which vaccine will be the best option against Omicron and other potential variants. The spike protein of the virus is the primary target of the vaccines to produce immunity in humans and this variant has more mutations in the spike protein than any other variant.
Another query that arises is with regards to current treatment strategies and treatment protocols for COVID-19. Will the same drugs work or will we need to modify our management guidelines for Omicron?
Lastly, do we need to come out with more sensitive and specific diagnostic tests to detect the disease early? Will the current test kits detect the COVID-19 variants? In some of the PCR tests, one of the target genes is not detected in Omicron (S gene dropout).
With so many uncertainties at this point of time, the heavily-mutated Omicron is an enigma and certainly a Variant Of Concern. Meanwhile, preventive measures like masks, social distancing and hand hygiene remain our best options. The government agencies need to increase surveillance, intensify public health measures and share information on database platforms globally in our collective endeavour to fight the pandemic.
(Dr Monica Mahajan, Director Internal Medicine, Max Healthcare, New Delhi)