(ORDO NEWS) — The authors of the report emphasize that their statistics apply only to symptomatic illness, since the level of protection of booster vaccinations against severe Covid-19 and hospitalizations due to omicron is expected to be higher.
The effectiveness of revaccination against the omicron strain of coronavirus, more precisely, the symptomatic disease caused by it, falls after 10 weeks. This is faster than the delta option. This conclusion was made by experts from the UK Health Protection Agency (UKHSA), whose report was published a few days ago.
The analysis was based on data on 147,597 cases of delta and 68,489 cases of omicron, as well as information on vaccinations in the United Kingdom, in particular booster shots from AstraZeneca, Pfizer and Moderna. According to experts, each vaccine has been less effective against the new variant – compared to the delta strain – over time, but to varying degrees.
For those initially vaccinated with AstraZeneca, an additional dose of mRNA-based vaccines – from Moderna and Pfizer – protected omicron-induced symptomatic Covid-19 with 60 percent effectiveness two to four weeks after injection.
But after 10 weeks, this figure for Moderna was down to 45 percent, for Pfizer to 35 percent. For those vaccinated with three doses of Pfizer, efficacy was 70 percent against the omicron variant one week after booster, but after 10 weeks it had dropped to 45 percent.
Those who received the Pfizer vaccine the first two times and then received a booster dose of Moderna were protected from symptomatic illness due to the omicron at about 75 percent for all nine weeks after the third vaccination.
The level of protection of revaccination for those who initially received Moderna was not possible to assess due to the insufficient number of participants. After two vaccinations, their effectiveness dropped to zero by the 20th and 24th weeks (while against the delta strain, it almost reached 80 percent).
The authors of the report emphasize that their statistics only apply to symptomatic illness, as protection against severe Covid-19 and hospitalizations is expected to be higher and lasting in revaccinated patients. However, in order to draw unambiguous conclusions about this, you will have to wait a few more weeks until information appears.
“For previous strains of coronavirus, the effectiveness of the vaccine against severe illness, including hospitalization and death, was significantly higher than against mild illness. <…> After the appearance of the “delta” in the UK, early estimates of the effectiveness of two doses of vaccines against the mild form of coronavirus infection suggested a significant decrease – compared with the alpha strain. However, the analysis of the level of protection from hospitalization did not show a drop when comparing these two options, ”added the agency’s specialists.
They also recalled that, according to the latest findings of scientists, patients with omicron are about 50 percent less likely to be hospitalized – if, again, compared to the delta. According to other sources, this figure reaches 80 percent.
With the emergence of new data on the omicron strain, some countries have begun to speculate about the introduction of fourth vaccinations. Israel, for example, has already announced fourth-dose vaccinations for citizens over 60 and health workers.
The UK authorities are planning to await the results of studies on how vaccines protect against severe Covid-19 caused by a new variant of the virus. And Anthony Fauci, chief scientific adviser to US President Joe Biden on the pandemic response, called such measures premature.
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