Why an Omicron wave may not be as severe as Delta

Why an Omicron wave may not be as severe as Delta

28.12.2021

Though the Omicron coronavirus variant has spread rapidly around the world since it was first detected in South Africa, findings from several new studies suggest it may not be as deadly as the Delta variant, which drove the catastrophic second wave in India. However, vaccination, booster shots and wearing masks remain the key weapons in our arsenal against the new variant. A look at some new developments in research on Omicron

Omicron more contagious but infection likely milder

Three new studies in South Africa, Scotland and England have found that Omicron is causing milder infections than previous variants and is less likely to cause hospitalisation. That’s good news given that the highly contagious nature of the variant is likely to lead to a surge in cases around the world.

Until now, the severity of illness from Omicron was unclear. But these new studies indicate that some biological features specific to the Omicron variant of SARS-CoV-2 make it less dangerous than Delta. Coupled with immunity in the general population because of previous infections and vaccination, experts believe fewer patients will require hospitalisation in the next wave of cases. Though Omicron has been observed to evade antibodies from a previous infection, it may not be able to escape the powerful but slower immune responses that prevent serious disease.

The South African study reported a 70% lower chance of hospitalisation from Omicron compared with other variants, while the Scotland study found a two-thirds reduction in hospitalisation risk compared with Delta. The English study, however, only reported a 15%-20% reduction in hospitalisation and a 40%-45% reduction in the risk of hospitalisation for more than a day.

But the researchers cautioned that results of their studies were still preliminary and Omicron is still likely to cause a large number of hospitalisations, particularly among vulnerable groups and unvaccinated people, given how quickly it is spreading.

The best defence against Omicron is vaccination. Two doses plus a booster shot are likely to provide strong protection against infection and severe illness. But most countries are yet to fully vaccinate a majority of their populations and only a handful, including the US, UK and Australia, are administering booster shots to the general public.

India is far better prepared to face an Omicron wave than it was against the Delta wave earlier this year. In April, during the peak of the Delta surge, just 1.9% of Indians were fully vaccinated and 7.1% partially vaccinated. As of December 23, 41% of Indians are fully vaccinated and another 19% has received at least one dose for a total 60% vaccination coverage.

Loss of taste, smell unlikely but symptoms show up early

Early data shows that Omicron is causing largely the same symptoms as previous variants. Though there are some differences, researchers are still unsure of their impact on the course of the illness.

In South Africa, for instance, those infected with Omicron tended to develop a scratchy or sore throat along with nasal congestion, a dry cough and muscle pain, especially low back pain. But these symptoms have also been reported in infections from Delta and the original coronavirus.

One subtle difference is that Omicron is less likely to cause a loss of taste and smell. Data from Norway found that just 23% of Omicron patients reported a loss of taste and 12% a loss of smell.

A researcher in the US found that vaccinated people with Delta or the original coronavirus generally reported headaches, congestion, sinus pressure and pain, while unvaccinated people were more likely to report shortness of breath, coughing and other flu-like symptoms. It’s likely to be the same with Omicron among vaccinated and unvaccinated patients.

Omicron also appears to have a shorter incubation time. It can take as little as three days before an infected person develops symptoms, becomes contagious and tests positive compared with four to six days for Delta. Omicron likely has specific mutations that allow it to quickly invade cells.

Omicron wave shorter in South Africa

The discovery of Omicron in South Africa last month sent alarm bells ringing around the world, but officials and experts say its wave has already peaked, suggesting Omicron waves may not be long-lasting ones. Earlier in December, the country saw a sharp spike in cases and positivity rate but despite opting against severe lockdowns and other restrictions, the wave has begun to subside Though several countries imposed restrictions on travellers from southern Africa, many still reported Omicron cases within the community, suggesting the variant was already active, if undetected, in other parts of the world.

But South Africa’s subsiding Omicron wave, in addition to a possible lower risk of severe illness and hospitalisation despite a lagging vaccination programme, holds promise for other countries experiencing Omicron outbreaks. The US and parts of Europe, where Omicron is making up a vast majority of new cases, have far greater vaccination coverage.

Data from South Africa suggests its Omicron wave is about two to three weeks ahead of the US, two weeks ahead of Norway and Denmark, and up to four weeks ahead of the UK.

Source: NYT, Economist, media reports