According to new data released yesterday by the British Health Insurance Agency, there are indications that protection against booster doses against symptomatic Covid-19 infection due to Omicron is beginning to weakens after about ten weeks. According to the UK Health Security Agency, it will take a few more weeks to evaluate the effectiveness of booster doses against the risk of hospitalization and death following Omicron infection. But he estimates that “based on experience from previous variants, protection is likely to be significantly higher than against symptomatic disease.”
A new report from Britain, which analyzed data from people vaccinated with Pfizer / BioNTech, Moderna or AstraZeneca, comparing 148,000 Delta cases and 68,000 Omicron cases, according to the New York Times, confirmed that both vaccines – both as well as the third- are less effective and weaken faster against Omicron than against Delta.
Among those who took two doses of AstraZeneca, the third dose followed by Pfizer or Moderna mRNA vaccine (a combination that affects many people over 60 in Greece), two to four weeks after the booster dose was 60% effective in preventing the disease. with symptoms. After ten weeks, however, the effectiveness of the third dose of Pfizer had dropped to 35% (always against the possibility of symptomatic disease), while Moderna to 45% after nine weeks.
In those who took three doses of Pfizer, the efficacy against the symptomatic disease dropped from 70% one week after the booster dose to 45% after ten weeks. In the best position were those who had taken two doses of Pfizer and then a third dose of Moderna, with the effectiveness of the vaccine being estimated at 75% after nine weeks.
Omicron must be 90% less serious than Delta to avoid a new wave of hospitalizations
The Omicron variant of the coronavirus must be about 90% less severe than the Delta, in order to prevent a new large wave of hospitalizations in the winter, similar to the peak of previous waves, according to estimates by the Sage Scientific Advisory Group for Emergencies) of the British Government.
This assessment, according to the British “Independent”, is based on the assumption that there will be no further restrictions or significant changes in the behavior of the population in winter. The estimate should also be evaluated in light of the fact that, based on two new British studies, it appears that people infected with Omicron are 40% to 70% less likely to be admitted to the hospital compared to the Delta variant.
But both of the above studies – one from Imperial College London and one from Scotland – are based on a small number of Omicron cases, especially in people over 60 who are at higher risk of becoming seriously ill and in need of treatment. Thus, for the time being, uncertainty remains as to whether Homicron is inherently less pathogenic or whether it appears so because a large part of the population is immune to vaccines.
Scientists know that despite its apparent mildness, Omicron’s immune-defying abilities, combined with its high transmissibility, mean it has the potential to infect millions of people during the holiday season. Even if a smaller percentage become seriously ill than would have happened with Delta, this percentage can still be large enough in absolute numbers to worry health systems. It is still impossible to make a reliable mathematical-epidemiological prediction of where “the ball will land” in terms of the number of future hospitalizations due to Omicron.
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