Omicron risk still unclear: Fingers crossed as cases rapidly rising in Europe and South Africa
Early studies suggest that Omicron variant can escape the neutralising antibodies to some extent and a considerable number of people are getting infected a second time with it
It’s been close to three weeks since the Omicron variant of Coronavirus was identified. India has so far reported about 40 sequences confirmed cases of Omicron. Virologists believe there may be many more in the community and that it would take weeks to understand how the current surge in Omicron infections would affect hospitalisation.
In India, there have been reports of about 40 sequence confirmed cases of Omicron, but there may be many more in the community. “At this stage, the government should increase cluster-based testing, and most importantly speed up vaccinations,” asserted Dr Shahid Jameel, a fellow at OCIS and Green Templeton College, University of Oxford, and a visiting professor at Ashoka University.
It has now been seen that Omicron is transmitting quite fast and has become the predominant strain. “This means that Omicron has high transmissibility. It is also becoming clearer that it will affect people who are even double vaccinated. The cases are also rising in Europe amongst the unvaccinated. Omicron is becoming the predominant strain,” stressed Oommen John, a senior public health specialist at the George Institute of Global Health.
In South Africa, where it was first identified, the Omicron variant is displacing the Delta variant and causing a sharp rise in cases. It has also been found that the Omicron variant can cause reinfection. A study by Juliet Pulliam of Stellenbosch University showed that a considerable number of South Africans who had tested positive for Covid-19 during previous waves as a result of Beta and Delta variants are getting infected a second time with Omicron.
The previous study underscored that questions remain regarding whether Omicron is also able to evade vaccine-induced immunity and the potential implications of reduced immunity to infection on protection against severe disease and death.
Data on the virulence of the variant shows that in hospitals those affected with Omicron have not shown a pattern of higher disease severity amongst older people. This could change as more people get affected, but the data, as of now, shows otherwise.
In South Africa’s Tshwane, amongst those admitted in the hospital after testing positive for Omicron, only 30% had severe cases. Earlier during the Delta wave, 70% of those between 50-69 and 90% of above-80s had severe cases.
In South Africa’s Gauteng province, where Tshwane is located, in-hospital mortality rates were also lower in the past four weeks compared to cumulatively (2.6% compared to 22%) and younger patients (0-9, 10-19, and 30-39) accounted for higher hospital admissions during the past month than previously. The average length of stay in the hospital, for all age categories of patients, was lower in the past month.
However, Jameel pointed out that Omicron has the highest number of mutations seen in any Coronavirus variant so far, including 32 in the spike protein and 10 within a key region of this protein that is involved in virus entry into cells and its neutralisation by antibodies.
As of December 11, the European CDC has reported 732 sequences confirmed cases of Omicron.
Of this, Denmark had a big cluster, much of which remains to be confirmed by sequencing.
In the UK, there are a total of 3,137 confirmed Omicron cases. “However, if you look at the frequency of Omicron cases, it is still small – Austria (0.07), Norway (0.06) and Netherlands (0.02). In the UK on 11 December there were 633 new cases of Omicron out of 53,812 cases (frequency 0.11). But the numbers are rising rapidly and Omicron may displace Delta in the weeks to come,” explained Jameel.
Britain’s Health Security Agency reported how a person infected with Omicron is roughly three times as likely as a person infected by the Delta variant to pass the virus. The World Health Organization said on December 9 that some evidence had emerged that Omicron was causing milder illness than Delta, but that it was too early to be certain.
Early pre-print studies suggest that Omicron can escape the neutralising antibodies to some extent. The Omicron variant is transmitting faster in several areas than the Delta or earlier variants at a comparable time after their first detection. “In accordance with the above, in early laboratory results, Omicron is neutralised about 40 times less effectively by antibodies made in people who had prior infection or are vaccinated. There is so far no information on how well the other part of our immunity based on killer T cells controls the Omicron variant,” warned Jameel.
In the coming weeks, we will know about Omicron severity, but vaccines appear weak against Omicron reinfection. A study based on computer models by Billy Gardner and Marm Kilpatrick from the University of California suggest that after two doses of an mRNA vaccine (Pfizer/BioNTech or Moderna), the efficacy against symptomatic infection from Omicron is only about 30%, down from about 87% versus Delta. The invasion of Omicron is likely to result in widespread infection, and substantial hospitalisations unless widespread boosting of immunity occurs, the study noted. The pre-print was published on medRxiv.
A study published by British government scientists of how vaccines hold up against the Omicron variant showed that four months after people received a second dose of the Pfizer-BioNTech vaccine, vaccine shots were around 35% effective in preventing symptomatic infections caused by Omicron. Two doses of the AstraZeneca vaccine appeared to offer no protection against symptomatic infection caused by Omicron several months after vaccination. Both the vaccines performed better against the Delta variant. A third dose of the Pfizer-BioNTech vaccine, though, lifted the vaccine effectiveness to roughly 75%.
There could be a false sense of security in those who have been vaccinated, maintains John, and they shouldn’t lose guard. “There is still a perception that foreign travel is required to be infected with this variant. We need to be vigilant. The government has already notified districts to identify those infected with the variant,” explained John.
Vaccines do not protect very well from re-infection by Omicron but they continue to protect from severe disease. Virologists have insisted that before India starts on booster shots, it should vaccinate more people with two doses. “But India should also make a policy on boosters – who will get it, when they get it and what vaccine will be used for boosters,” said Jameel.