By Dr. Satish K Gupta*
What we should know about BA.2.75? How far will it go?
Several omicron subvariants have been circulating globally, including BA.1, BA.2, BA.2.12.1, BA.2.75, BA.4, and BA.5.
The order or naming is not the order of evolution but rather based on lineage.
BA.4 and BA.5 are driving Covid waves in Europe and USA while BA.2.75 is the main culprit in India.
Why BA.2.75 is scary?
Presently it is the most highly evolved variant of Omicron. It has the highest number of mutations, even more than BA.5.
Why cases by BA.2.75 are rising?
SARS-CoV-2 is prone to mutations. Only the higher versions survive. BA.2.75 is one such example. It has
1. Immune Escape: It can infect even those who have Neutralising Ab against previous variants.
2. Better binding affinity to ACE-2 receptors. So it can outcompete older variants.
3. Higher transmission rates.
What does Immune Escape mean?
It means that it can infect even those who have been fully vaccinated against Covid -19. Also, the past infection does not confer protection against BA.2.75 infection.
It means that the entire population is susceptible to new the Variant. That is why the present positivity rate in Delhi is around 15%. It is to be noted that the peak positivity rate in the Delta wave was around 25%.
Does it mean that Vaccines have been rendered useless?
No, the effects of vaccination or past infection are protecting people from severe disease. It is because of mass vaccination that although the cases are rising most cases are remaining mild.
No hospitalization surge by BA.2.75
So far, India isn’t seeing a significant rise in hospitalizations from its ‘Centaurus’ because of the combined effects of high rates of vaccination and of the previous infection. This hybrid immunity is going to largely protect and keep people out of hospitals.
Higher and higher population immunity leads to less and less severe consequences for most people.
But we need to take care
The high frequency of infection waves could mean general disruption caused by high levels of illness in short term and more long COVID in times to come.
Why so many names?
Omicron subvariant BA.2.75 — nicknamed ‘Centaurus’ by some and ‘Scariant’ by others by some scientists on social media.
What does World Health Organization have to say about it?
World Health Organization (WHO) has categorised it as a Variant Of Interest (VOI) not a Variant of Concern (VOC).
BA.2.75 in India
India seems to be at the epicentre of the spread of BA.2.75. This mutation-laden lineage evolved from the BA.2 subvariant of Omicron, which spread widely in early 2022. BA.2.75 has been detected in more than 20 countries worldwide.
Researchers in India have sequenced more than 1,000 samples of the variant since May 2022. The data suggest that about two-thirds of new cases there are currently caused by BA.2.75. A study in Delhi’s prime Covid hospital Lok Nayak Jai Prakash Narayan Hospital involved 90 patients and over half of the samples have been detected with BA 2.75.
BA.5 is the main driving Variant in Europe and the USA
BA.2.75 has been detected at relatively low rates outside India, in countries including Japan, the United States and the United Kingdom, which are in the middle of or just past the peaks of surges caused mainly by BA.5.
Which is milder BA.5 or BA2.75 -Immune?
Escape of BA2.75 Versus BA.5
BA. 2.75 though has a higher number of mutations but is more benign than BA.5.
Both BA.2.75 and BA.5 subvariants can substantially escape neutralising antibodies induced by vaccination or previous infection, or both. However, importantly, BA.2.75 showed less capacity for escape from neutralisation than did BA.5, despite BA.2.75 having emerged after BA.5 and having more mutations in the spike protein.
Why BA.5 could not take over in India?
Indian’s immunity profile is part of the possible explanation. In 2021, the country saw an explosive wave of cases caused by the Delta variant, which shares a key mutation with BA.5. Possibly previous Delta infections provide added protection against BA.5, leaving an opening for BA.2.75.
How can we overcome the growing menace of the Variants?
It is possible that widespread Omicron infection gives local transmission immunity in the nasal mucosa.
Emphasise the importance of developing better vaccines with a pan-sarbecovirus neutralising capability to counter future SARS-CoV-2 variants.
What can I do till the time a PanCorona vaccine is developed?
Use masks like an umbrella. Whenever there is news of rising cases or trends of a new wave pull up your masks as you look for an umbrella in the rainy season.
*Dr Satish K Gupta is an MD in Medicines, a Visiting Senior Consultant Physician and Internist at Max Super Speciality Hospital, and a Clinical Assistant Professor at GS Medical College, Chaudhary Charan Singh University, Meerut. He is the author of Journey of COVID in India: A Doctor’s Perspective.