Booster protection against symptomatic COVID-19 caused by Omicron lasts about 10 weeks, data shows.
It may mean fourth doses in 2022 — depending on whether protection holds against severe COVID-19.
Immunocompromised Americans can already get an extra shot.
Booster protection against symptomatic illness caused by the Omicron variant dropped by up to 25% within 10 weeks, new real-world data found — though it's not yet clear whether everyone may need further doses in 2022.
The UK Health Security Agency said protection against symptomatic COVID-19 caused by the variant dropped from 70% to 45% after a Pfizer booster for those initially vaccinated with the shot developed by Pfizer with BioNTech.
In the same analysis published on Thursday, the agency found the effectiveness of Moderna's booster paired with two doses of the Pfizer vaccine held at 70% to 75% for up to nine weeks, though not many people in the study received this regimen, which could affect the accuracy of the finding.
For those fully vaccinated with AstraZeneca's vaccine, booster effectiveness dropped from 60% to 35% with a Pfizer booster and to 45% with a Moderna booster after 10 weeks, the UKHSA said.
Eric Topol, the director of the Scripps Research Translational Institute, tweeted on Thursday that the UK findings were a "replication" of what had been seen in Israel.
—Barak Raveh (@BarakRaveh) December 24, 2021
On Wednesday, Israel became the first country to announce fourth doses to try to bolster immunity against Omicron for those most susceptible to COVID-19, including people older than 60 and health workers.
But other countries, such as the UK, are holding tight for more data on how well existing regimens work and the safety and effectiveness of additional doses.
In the US, most immunocompromised people could already get a fourth dose from six months after the third, before Omicron emerged. Those who got Johnson & Johnson's single-dose vaccine initially aren't recommended more than two doses, guidance from the Centers for Disease Control and Prevention said.
Dr. Mary Ramsay, the head of immunization at UKHSA, told The Independent that the UK wouldn't rush into changing its policy on vaccination until it had clarity on whether the protection against severe disease was affected by Omicron.
The agency said it would be a few weeks before booster protection against severe COVID-19 caused by Omicron could be estimated because there hadn't been many people getting sick from it. "However, based on experience with previous variants, this is likely to be substantially higher than the estimates against symptomatic disease," it said.
Adam Finn, a member of the group of experts who advise the UK government, told LBC radio on Friday that the committee would provide recommendations "at some point in the New Year."
"We do need to see how things go through this wave and beyond. I think there may well be people who received their boosters early who are in the older, more vulnerable age groups who may need a further jab — that has not been decided yet," he said.
To get to the figures, the UK researchers compared the vaccination rates in people who had tested positive for Omicron on a lab test with those who tested negative between November 27 — when the first Omicron cases were detected in the UK — and December 17. People with foreign travel were excluded from the analysis.
In the meantime, the experts said the priority to tackle Omicron was still to vaccinate people who weren't vaccinated and get boosters into as many people as possible.
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