December 11, 2023

Athens News

News in English from Greece

Omicron: Expert Uncertainty with Pathogenicity Assessment

The Sage Scientific Advisory Group estimates that the Omicron variant of the coronavirus should be about 90% less pathogenic than the Delta strain. However, not all so simple. The protection against Omicron has been found to weaken after 10 weeks.

Epidemiologists, based on two new British studies, found that people infected with Omicron are 40-70% less likely to go to the hospital compared to those with the Delta variant.

Two large studies conducted, one by Imperial College London and the other in Scotland, are based on a small number of cases of the Omicron strain, especially among people over 60 who are at higher risk of severe illness and need treatment (hospitalization).

Thus, it remains unclear at this time whether Omicron is inherently less pathogenic or appears to be less pathogenic due to the population’s susceptibility to vaccines.

Scientists know that despite its apparent “lightness”, Omicron’s immune abilities, combined with its high transmissibility, mean that it can infect millions of people during the holidays.

Even if a much smaller percentage of citizens become seriously ill (than would be the case with Delta), it could still be large enough in absolute numbers to worry health systems. It is still impossible to make a reliable mathematical and epidemiological forecast in terms of the number of future hospitalizations of citizens infected with Omicron.

According to new data released yesterday by the British Health Protection Agency, there are signs that protection for an additional (booster or boost) dose to counter symptomatic Covid-19 infection from Omicron is starting to wane after about ten weeks.

According to the UK Health Security Agency, it will take several more weeks to assess whether booster doses of vaccine provide protection in terms of the risk of hospitalization and death from the Omicron variant. Epidemiologists-experts believe that, “based on the experience of previous options, the protection provided by the vaccine (the production of antibodies) is much more effective than after suffering a symptomatic illness.”

Effectiveness of vaccines
A new UK report that analyzed data from people vaccinated with Pfizer / BioNTech, Moderna or AstraZeneca comparing 148,000 Delta cases to 68,000 Omicron cases, according to the New York Times, confirmed that both vaccines two and three are less effective and weak against Omicron than against Delta.

Those who received two doses of AstraZeneca, followed by a third dose of Pfizer or Moderna mRNA vaccines, were 60% more protective after two to four weeks. Although ten weeks after the third dose given by Pfizer, antibodies dropped to 35% (always taking into account the possibility of symptomatic illness), while Moderna dropped to 45% after nine weeks.

For those who took three doses of Pfizer, efficacy against symptomatic illness dropped from 70% one week after the booster shot to 45% after ten weeks. Those who took two doses of Pfizer followed by a third dose of Moderna were in better position, with the vaccine estimated to be 75% effective after nine weeks.

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