Omicron vs. Deltacron: We can only be certain, two years after the pandemic began, that the Sars-CoV-2 virus that is responsible for Covid-19 is constantly changing. There have been four variants of the virus since the outbreak started in December 2019. These are Alpha, Beta, Gamma, Delta, and now Omicron.
Omicron, though the new variant is labelled by the World Health Organization (WHO) as “highly transmissible,” was declared as such by the WHO in November 2021. As a result, there have been recorded numbers of cases in several countries since then.
Omicron might remain lower in death toll than previous waves, including that caused by Delta, as cases rise around the world – the United States has been averaging 800,000 new infections every day.
Scientists said it was responsible for the spike in infections in South Africa last year, as a new variant of Coronavirus was detected there at the end of November. At the time, experts in South Africa said that some infected people do not display symptoms.
Omicron was dubbed as a highly transmissible variant by the WHO.
A variant of the coronavirus has more than 50 mutations not previously seen together, including over 30 mutations that change the spike protein on which the virus attaches to cells. According to Reuters, vaccines in use today target the protein spike responsible for the symptoms. Therefore, Covid-19 vaccines may provide less protection against Omicron.
Is Omicron transmissible?
Omicron was found to be two to three times more likely to infect people, particularly in households, as compared to Delta in the early research on its transmission.
Associate professor of epidemiology Bill Hanage says Omicron is likely to cluster in large groups.
Omicron maybe 105% more transmissible than Delta, according to a study from France. Even if Omicron is less severe than Delta, most French hospitals may see higher activity, if not overload in the future because of the higher reproductive number – how many people can be infected at a specific time by an individual.
The increased risk of reinfection is another characteristic of Omicron. Omicron was 5.4 times more likely to reinfect than Delta, according to a study by Imperial College London.
Maria Van Kerkhove, WHO’s the technical lead on Covid-19, told a recently held press conference that Omicron was “efficiently transmitting” and detected in all areas with effective gene sequencing options.
Kerkhove explained that Omicron has led to a massive spike in cases. This is owing to its ability to adhere more easily to human cells, cause reinfection, and replicate in the upper respiratory tract. This set it apart from other variants like Delta.
It appears that Omicron is less likely to cause severe disease than Delta due to this combination of factors, she said. A leading infectious diseases expert, however, cautioned that the global health body is still seeing an increase in hospital stays and patients who require clinical care, which will place pressure on countries’ healthcare systems.
"The Omicron variant has been detected around the world. We are seeing a very sharp increase in case numbers with almost 10 million cases reported in the last 7 days." –@mvankerkhove explains why Omicron is transmitting so efficiently and how to contain the spread of #COVID19. pic.twitter.com/IIjb4rBoxX
— World Health Organization (WHO) (@WHO) January 8, 2022
How about severity?
When compared to Delta, the number of infections is higher, but the rates of deaths, and even hospitalizations, are lower.
There are several studies that support this, including one conducted by South African scientists. They discovered people who contracted Omicron for two months were 80pc less likely to require hospitalization. But scientists said the low hospitalisation rate in the country may also be linked to a high level of immunity.
One of the study’s authors, Professor Cheryl Cohen of the National Institute for Communicable Diseases, said the data show Omicron is less severe than other variants.
Separately, a study conducted by the UK Health Security Agency found Omicron was half as likely to result in hospitalization as Delta. According to their study, people who have received two and three doses of a Covid-19 vaccine have an 81% reduced risk of hospitalisation.
The number of Omicron patients who required hospitalization was 68pc lower than that of Delta patients in Scotland, according to researchers at the University of Edinburgh. In addition, they referred to the increased risk of reinfection – 7.6% of samples analysed had reinfections compared to 7% in the Delta study.
The risk of hospitalization for patients with Omicron was 40 to 45% lower compared to those with the Delta variant. This is according to another study conducted by Imperial College London.
Antonio Costa, Portuguese Prime Minister, announced the easing of curbs despite a record number of cases.
Health officials in India reported that only five to ten percent of the current wave of patients driven by Omicron were hospitalized. This is compared with 20 to 23 percent in the previous wave led by Delta.
In some countries, hospitalizations have not remained low. The number of people hospitalized with Covid in the United States on Jan 10 reached 132,646, surpassing the figure of 132,051 set in January 2021.
In France, hospitalisations have increased the most since April 2021, but remain below their peak from the end of 2020. According to the health minister, Omicron causes less severe complications, but hospitalizations are still on the rise since it is highly contagious.
Unlike the lungs, Omicron affects airways
The reason for the reduced severity may be due to the fact that Omicron multiplies faster in the airways and lower in the lungs.
At 24 hours after infection, a University of Hong Kong study found that the Omicron strain replicated around 70 times more than the Delta strain and the original Sars-CoV-2 strain. However, the Omicron variant replicated less efficiently (more than 10 times less) in the human lung tissue than the original Sars-CoV-2 virus, which suggests a weakened condition.”
Due to its increased transmissibility, the variant, however, poses a “very significant” threat overall.
The CTN reported that six separate studies found that Omicron does not cause lung damage as severe as Delta or other variants.
According to WHO Incident Manager Abdi Mahamud, there is increasing evidence that Omicron causes less severe illness because it affects the upper respiratory tract.
In an interview with Reuters, he said, “We are seeing more and more studies indicating that Omicron is infecting the upper body rather than the other variants that may cause severe pneumonia.”
Do existing vaccines provide protection against Omicron?
Multiple studies showed that getting a booster dose results in antibodies capable of fighting the new variant of Omicron even a few months after receiving two shots of a vaccine.
In an early analysis of real-world data, Head of Immunisation at the UK Health Security Agency, Dr Mary Ramsay, found that the risk of catching Omicron was “significantly reduced” following a booster vaccine.
Compared to the protection they provide against Delta, two doses of AstraZeneca or Pfizer-BioNTech vaccines provided much lower levels of protection against symptomatic infection.
Reuters reports that when boosted with the Pfizer vaccine, around 70% of those who had initially received AstraZeneca were protected against symptomatic infection, and 75% of those who had initially received Pfizer.”
Additionally, studies later confirmed that booster doses provided protection against Omicron.
According to Danish researchers, after receiving an injection of either the Pfizer vaccine or the Moderna vaccine, vaccine effectiveness can be restored when the booster dose of the Pfizer vaccine is administered.
Pharmaceutical companies have also conducted research that has shown promising results. In a lab test, Pfizer’s vaccine was able to neutralize the Omicron variant after three shots. The company’s CEO also stated that it will be able to release a vaccine for Omicron by March.
Booster doses of Moderna’s vaccine are effective against Omicron as they increase neutralizing antibodies 37-fold compared to pre-boost levels.
Despite supporting AstraZeneca’s vaccine third dose, a study by the University of Oxford concluded that it had improved neutralization rates.
Chinese vaccines such as Sinopharm and SinoVac, however, have not shown the same level of promise.
The University of Hong Kong and the Chinese University of Hong Kong jointly conducted a study that found that those who had received two doses of SinoVac but received the third dose did not have adequate levels of antibody protection.
According to researchers from Shanghai Jiao Tong University and a Shanghai-based laboratory, Sinofarm’s vaccine had “significantly lower” neutralizing activity against the Omicron variant. However, its efficacy against Omicron is unclear.
When administered after two doses of the original vaccine, Sinopharm’s protein-based vaccine significantly improved immune responses against various strains of Sars-CoV-2, including Omicron.
Additionally, there are other treatment options available this time around. The US Food and Drug Administration (FDA) has approved two antiviral pills, made by Pfizer and Merck.
In response, both companies said their pills would be effective against the new variant.