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The omicron variant of coronavirus has already displaced delta and is causing rising infection rates in many countries. Although disease courses are likely to be somewhat milder, vaccine protection is declining more rapidly.
“Omicron is not mild”
The Omikron variant, which is now dominant in Austria, with its many changes, especially in the spike protein that is important for docking to cells, changes the rules of the pandemic game. Compared to the delta variant, the significantly higher transmissibility and the “immune escape”, i.e. the ability to escape an existing corona immune protection, stand out. However, the risk of severe disease is likely to decrease, as data from England show.
WHO: Omicron has already displaced Delta
Just a few weeks after the first detection of the new variant, what experts had feared in view of the genetic mutations picked up by Omicron came true in many countries. The WHO classified Omikron as a Variant of Concern (VOC) on November 26, 2021. It has since displaced the previously dominant delta variant and is causing rising infection rates. The EU health authority ECDC estimates the risk as “high to very high” (as of January 7, 2022). The WHO warns that in two months, more than half of Europeans could be infected with Omikron.
Compared to earlier waves, however, there is also good news: initial, still preliminary data suggest a less severe clinical picture of the disease. For example, the WHO most recently cited studies indicating that omicron primarily affects the upper respiratory tract, such as the nose, throat, and bronchi, and less severely affects the lungs.
Apparently milder disease course in omicron
Data evaluated by UK health authorities also suggest somewhat milder disease progression. According to these data, the risk of ending up in an intensive care unit with Omicron is about half that of the Delta variant. The risk of a “normal” hospital stay drops to one third. Even though vaccination against Omicron is less effective than against Delta, according to the British figures, it significantly reduces the risk of severe illness (up to 19 percent compared with unvaccinated persons).
However, vaccination protection declines rapidly over time, as shown by a study of nearly 374,000 British corona cases. According to the study, a double vaccination with Biontech-Pfizer still protects more than 60 percent against symptomatic disease with the delta variant after five months (20 to 24 weeks). With Omikron, on the other hand, vaccine protection drops to around ten percent. Booster vaccination then increases efficacy again to almost 70 percent, but here, too, vaccine protection drops significantly after five to nine weeks.
Vaccination protection declines more rapidly
In Austria, complexity researcher Peter Klimek recently warned against calling Omicron a “mild” variant. He emphasized that it might be only slightly less dangerous than Delta when in contact with an unprotected population. The ECDC also stressed that the risk assessment could be different if more and more elderly people become ill as the wave of infection progresses.
In Austria, Omicron will affect a population of which only slightly more than half is likely to be protected against the new variant. The team around simulation researcher Niki Popper calculated the immune protection on the basis of vaccination data, infection figures and dark figure estimates with 55 percent of the population (as of January 1). By comparison, 80 percent of the population was protected against the delta variant, according to the “Model-Based Estimation of Immunization Levels in Austria.”
This is because Omicron, with its approximately 30 mutations in the spike protein and other regions of the pathogen, has a significantly increased ability to “immune escape.” However, studies show that protection against symptomatic disease is also likely to be very high relatively soon after booster vaccination. Even in those who have been recovering for some time, the “booster” significantly increases the number of neutralizing antibodies, as recently shown in a study published in the journal “Nature” by the Austrian virologist Florian Krammer, who works in the United States.
Booster vaccinations should counteract lockdown
Here also lies a key to why, despite high Omicron infection numbers, many experts expect the hospital toll to rise less than in previous waves. Popper estimates that up to 90 percent of Austrians have already had contact with the pathogen – whether through vaccination or infection. This could reduce the proportion of severe Covid 19 courses. The disadvantage is that experts cannot reliably estimate the number of new infections that would threaten to overburden the hospital system. They largely agree that the best way to flatten the coming steep infection curve is booster vaccinations.
Warning against overburdening healthcare systems
In any case, the ECDC warns that very high infection rates will overburden healthcare systems. In addition, high transmissibility could cause many people in health care and other important fields of work to be absent, and testing and contact tracing systems to be overloaded.
For all the differences from earlier variants, however, at least something remains the same: The most common symptoms of Covid 19 disease have not fundamentally changed from the Delta to the Omicron variant, according to data from the United Kingdom. The top five symptoms are still a runny nose, followed by headache, fatigue, sneezing and a sore throat.
- source: APA/picture: pixabay.com
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