What we know about Omicron variant so far

Two new outbreak analyses in UK said on Friday that early data provides no evidence of Omicron being milder.

Is Omicron more, less, or as severe as the other variants?

On transmissibility, it found that Omicron currently has a reproduction number (denoted as R) of 3, while Delta had 1. This implies one Omicron infection leads to three more, and those pass on to three more each – leading to 27 cases in just two rounds of onward transmission, while Delta would cause only three.(Reuters)

Two new outbreak analyses in UK said on Friday that early data provides no evidence of Omicron being milder. Both analyses take into account preliminary hospital data and infection patterns in thousands of people and one of them, by researchers from Imperial College London, found that the odds of being hospitalised with Omicron and Delta may be similar.

“The study finds no evidence of Omicron having lower severity than Delta, judged by either the proportion of people testing positive who report symptoms, or by the proportion of cases seeking hospital care after infection,” said a statement by the Imperial College’s MRC Centre for Global Infectious Disease Analysis.

The statement added, however, “hospitalisation data remains very limited at this time”. The second UK report was by the UK government’s Health Security Agency (UKHSA), which said, “there is no signal that supports a difference in the intrinsic virulence of the Omicron virus compared to Delta”.

But a briefing by health officials in South Africa offered some contradictory signals, suggesting the disease manifested less severely in the country, although they too added caveats of the data being preliminary.

South Africa’s deputy health minister Sibongiseni Dhlomo unveiled slides showing fatality ratio in all age groups infected with Omicron at present was a third of the numbers seen during the previous two waves in the country, which were caused by the Beta and the Delta variant. Experts, however, said the SA officials’ calculating fatality ratio at 25 days may be premature.

But where experts from all around the world have agreed is that Omicron is significantly more transmissible and resistant to immunity.

The Imperial College’s report builds on that, using larger sets of infection data from UK than a similar report released by government experts one week ago.

On transmissibility, it found that Omicron currently has a reproduction number (denoted as R) of 3, while Delta had 1. This implies one Omicron infection leads to three more, and those pass on to three more each – leading to 27 cases in just two rounds of onward transmission, while Delta would cause only three.

On immune resistance, the Imperial College assessment found protection from Covid-19 offered by a past infection plummeted to 19%, compared to 85% with other variants. Similarly, vaccine efficacy, dropped to 0-20% after a two-dose course of the AstraZeneca or Pfizer vaccines.

What does this mean for India?

Niti Aayog’s VK Paul used a simple but effective extrapolation of per capita infection rates seen elsewhere to illustrate how significant a threat Omicron could be for India.

“If we see the number of cases in UK yesterday, it would translate to 1.4 million cases a day in India… If we see the number of cases, it is equivalent to 1.3 million cases in India’s population,” he said at the health briefing on Friday.

The implications of such a large spread, even for a country where at least two-thirds of the population is estimated to have had a past infection and where at least 87% have taken one dose of the vaccine, can be further whittled down to specific outcomes.

Hospitals face a significant threat

For this factor alone, there are several reasons. First, being there is still an estimated population of over 110 million adults without any Covid-19 vaccine dose.

Severe cases among this population added to the likely (albeit significantly lower) hospitalisation among breakthrough or repeat infection cases, especially among the elderly and those with compromised immunity, could still be a significant number in a country of 1.3 billion people.

But the bigger threat may be from staff shortages of the nature being predicted in the UK. England’s chief medical officer Chris Whitty said there could be significant gaps in hospital staff duty because of the “very sharp peak” of Omicron that is expected over the next month.

Health care workers in India, unlike a large proportion in the UK, are yet to receive booster doses.

Testing likely to be strained

Depending on how government mandates testing in its policy tweaks – for example, will all close contacts of Omicron cases need to be tested compulsorily as they are now – a large outbreak could stretch India’s testing infrastructure to beyond its capacity.

UK, which has registered record number of new cases in the past two days, is carrying out 18 tests per thousand people, according to Our World in Data. The corresponding number for India at present is 0.86 and, at its peak during the second wave, it was 2.26 per thousand people.

Effect on children and elderly unknown

India is yet to open vaccination of children or allow boosters to any part of the population, including the elderly who began to be covered early last year.

Children are likely to remain significantly less at risk due to their inherent immunity advantage, experts have said recently, but a highly transmissible virus will breach deeper into the population, posing a greater threat to any child with compromised immunity.

Experts have also called for boosters to be allowed to the elderly, who would likely have seen some drop in antibody levels as are typical of all vaccines after a period of 6-8 months. More data on how much more severe Omicron is inherently and details of severe disease even in vaccine breakthrough cases will hold the key to understanding the sort of threat that it poses for both these populations.