The analysis of public data also found that vaccination offers
strong protection against hospitalisation and severe illness after omicron
infection, helping to prevent the worst outcomes even as infection rates in
Britain soar to record levels.
The findings represent some of the largest sets of real-world
data to be released since the highly contagious variant was first discovered in
late November, and adds to a growing body of evidence that omicron may not
present as great a danger of hospitalisation and severe illness to the public
as earlier variants.
“The latest set of analysis is in keeping with the encouraging
signs we have already seen,” said Susan Hopkins, chief medical adviser at the
UK Health Security Agency, which issued the report.
The risk of being admitted to a hospital for omicron cases was
65% lower for those who had received two doses of a vaccine, compared with
those who had not received any vaccination.
The rate of hospitalisation was even lower among those who had
received three doses of vaccine, according to the report. People who had
received booster doses were 81% less likely to be admitted to the hospital,
compared with unvaccinated people, according to the agency.
The agency analysed 528,176 omicron cases and 573,012 delta
cases between Nov. 22 and Dec. 26 to assess the risk of hospitalisation in
England. Researchers included all cases diagnosed in the community and then
assessed the risk of general admission to the hospital or admission through
emergency care.
In a second study, the agency examined just symptomatic cases,
linked with hospitalisation data, and found that three doses of a vaccine
reduced the risk of hospitalisation for people with the omicron variant by 88%
compared with unvaccinated people with that variant.
While the results were encouraging, the agency said it would
take more time to assess the severity of omicron infections after admission to
the hospital.
Nicholas Davies, an assistant professor of mathematical
modeling at the London School of Hygiene and Tropical Medicine, cautioned that
the report covered mostly a younger mix of patients. “The omicron wave is
starting in younger people,” he said. “It’s important to bear in mind that
we don’t have much data on risks in older people yet.”
But he added that the findings were still encouraging, saying:
“It does look like people are experiencing less severe outcomes.”
Health officials have noted that omicron presents a challenge
because of the sheer speed at which it is moving through the public. Vaccines
are less effective at preventing infections than had been the case with other
variants, according to the findings.
“Vaccine effectiveness against symptomatic disease with the
omicron variant is significantly lower than compared to the delta variant and
wanes rapidly,” according to the report. “Nevertheless, protection against
hospitalisation is much greater than that against symptomatic disease, in
particular after a booster dose, where vaccine effectiveness against
hospitalisation is close to 90%.”
The findings help explain why there has not been a surge of
patients being rushed to the hospital even as the number of infections in
England has surpassed any wave that has come before.
Peter Openshaw, a member of the UK’s New and Emerging
Respiratory Virus Threats Advisory Group, said Friday that transmission of the
new variant requires only a small exposure.
“Omicron is so infectious,” Openshaw told the BCC. “We’re
lucky really that it wasn’t this infectious when it first moved into
human-to-human transmission. It almost needs just a whiff of infected breath and
you could get infected.”
During the week before Christmas, coronavirus infections
increased across all regions of England, according to the Office for National
Statistics. London was the epicenter, with an estimated 1 out of every 15
people infected in the week before Christmas.
At the same time, the National Health Service reported that
the number of hospital staff members absent from work was up 31% from the week
before, with 24,632 workers either sick or having to isolate.
“The wave is still rising and hospital admissions are going
up,” England’s chief medical officer, Chris Whitty, warned in a post on
Twitter.
In issuing its technical findings, the health agency noted
that its report did not address how the variant would affect the ability of the
health care system to function. Experts have noted that the sheer number of
infections could still cause a surge of patients that would overwhelm
hospitals.
But the data released by the agency did offer encouraging
signs for people worried about their individual risk and yet more evidence that
vaccinations are still playing a key role in keeping people from the worst
outcomes.
And it seemed to be in line with studies coming from South
Africa and Denmark, where omicron is believed to have had a bit more time to
work its way into the populations.
In a number of laboratory studies, scientists found evidence
suggesting that T cells in vaccinated people can put up a strong defense
against the variant, which could help prevent severe disease, hospitalisation and
death.
The South African government said Thursday that data from its
health department suggested that the country had passed its omicron peak
without a major spike in deaths, offering cautious hope to other countries
grappling with the variant.
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