Which is the most dominant strain of SARS-CoV-2 across the world right now? While Delta ruled the charts last, taking millions of lives and infecting even more, the WHO is now stating that Omicron - the newly discovered variant of Covid-19 first reported by researchers in South Africa in November, is rapidly taking over Delta as the dominant variant across the world.
According to a senior health official at the WHO, there is increasing evidence that Omicron, which the global body identified as a 'variant of concern' (VOC) on November 24, has the ability to evade immunity and infect patients. However, it has also been noted that the severity of disease caused by the variant is less when compared to previous variants.
Is Omicron overtaking Delta as the dominant strain?
While it might still take time for Omicron to become the dominant stream in every country, WHO's Covid body chief Maria Van Kerkhove said that Omicron is likely to have reached every country. She confirmed that it has been detected in every single country sequenced by the WHO. Being dubbed three times more infectious than Delta, Omicron might replace Delta as the dominant variant in a very short span of time.
Indian researchers made similar statements in the past week. The potential of Omicron to spread at such massive scales makes the threat level very high globally, especially in regions with low population immunity, a bulletin released by the Indian SARS-CoV-2 Genomics Consortium (INSACOG) noted, adding that global Covid-19 outbreaks had shifted from Delta to Omicron.
"Omicron has a clear growth advantage over Delta with the highest level of immune escape so far as well as high intrinsic transmissibility, leading to larger outbreaks than seen with Delta," the bulletin which released on Monday read.
(Doctors walking inside a Covid-care facility in Delhi during the second wave in 2021 | Image Credit: PTI)
INSACOG's statement resonated with WHO's update which stated that Omicron has a substantial growth rate and is outpacing other variants.
“This variant has been shown to have a shorter doubling time as compared to previous variants, with transmission occurring even amongst those vaccinated or with a history of prior SARS-CoV-2 infection; there is increasing evidence that this variant is able to evade immunity,” the update said.
Is Omicron more severe than Delta?
Most current data and research seems to show that Omicron does not cause severe disease or hospitalisation. The WHO has previously said that the symptoms of the Omicron are mild. Despite large numbers of Omicron cases in Delhi, for instance, oxygen beds and Covid-wards remain empty, as opposed to last year when the explosive Delta variant spread led to hospitals running out of oxygen and beds.
Citing global data, INSCAOG said that estimates of the severity of illness associated with Omicron are lower than seen in previous outbreaks.
Several studies have suggested that the Omicron causes less severe disease. A non-peer-reviewed retrospective cohort study from the US found that while the absolute number of cases and hospitalisations among children are currently increasing in the US, the risk of hospitalisation still remains lower compared to other age groups during the period when Omicron is circulating as compared to the period when the Delta variant was dominant.
Is Omicron 'mild'?
While Omicron has shown to have lower rates of hospitalisations and severe disease so far, experts have not ruled out the possibility of future harm. Experts agree that the Omicron has been able to breach vaccine immunity but also stress that vaccine and natural immunity may have played a role in why infected populations are experiencing milder symptoms. Studies have shown that Omicron is affecting those with comorbidities or without any dose of the Covid-19 vaccine more severely than vaccinated persons.
(A health worker administers a Covid-19 vaccine to a teenager, in Mumbai | Image Credit: Dinesh Parab/Outlook)
The WHO said that current estimates suggest Omicron should be "interpreted with caution due to potential biases, these preliminary results provide evidence of reduced overall effectiveness of vaccines against the Omicron variant, with greater declines in effectiveness with increasing time since vaccination, relative to Delta".
Despite a failure to provide protection against infection, In the UK, studies show that individuals who have received at least two doses of either AstraZeneca/Covishield or mRNA vaccines have remained substantially protected against hospitalisation. While the WHO has said that booster shots appear to boost immunity, it added the need for further conclusive studies on the same.
WHO's Kerkhove said that while hospitalisation rates were low at present, Omicron could penetrate vulnerable populations across the world and in which case “we will see an increase in hospitalisations and deaths". She further implored the world to treat the virus seriously and not just dismiss it as a cold. "The narrative that it is just mild is not true. So we have to really fight against it. It’s not the time to give up," Kerkhove said.
(With inputs from Agencies)