COVID-19 Variants Identified In The UK - 14 January 2022

UKHSA publishes updated Omicron risk assessment and analysis on vaccine efficacy, sub-lineage and symptoms

The UK Health Security Agency (UKHSA) has published a new variant technical briefing containing an updated Omicron risk assessment, alongside analysis on vaccine efficacy, sub-lineages and symptoms.

The updated risk assessment includes indicators for infection severity in both adults and children.

There is now high confidence that the Omicron variant causes low severity of disease in adults. However, confidence levels for severity indicators for children are low because further analysis is required to compare the risk of hospitalisation between Omicron and Delta, and to assess the clinical nature of illness in children.



BA.2 sub-lineage
As of January 10 2022, 53 sequences of the BA.2 sub-lineage of Omicron had been identified in the United Kingdom.

This sub-lineage, which was designated by Pangolin on 6 December 2021, does not have the spike gene deletion at 69-70 that causes S-gene target failure (SGTF), which has previously been used as a proxy to detect cases of Omicron. UKHSA are continuing to monitor data on the BA.2 sub-lineage closely.

Vaccine effectiveness
Vaccine effectiveness (VE) against Omicron has again been updated in this week’s briefing.

As previously published, data continues to show vaccine effectiveness against hospitalisation for Omicron remains high.

A booster dose was associated with a 74% reduced risk of hospitalisation in the first 2 to 4 weeks after vaccination, with the figure dropping to 66% 10 weeks or more after this dose. When combined with VE against symptomatic disease, the reduced risk of hospitalisation climbed to 92% 2 to 4 weeks after a third dose of the vaccine, down to 83% after 10 weeks or more.

There is further data showing that effectiveness against symptomatic disease is significantly lower compared to the Delta variant, and wanes more quickly.


Analysis shows that protection against symptomatic disease 2 to 4 weeks after a booster dose ranges from around 65% to 75%, dropping to 55% to 65% at 5 to 9 weeks – and 45% to 50% 10 weeks or more following the booster dose.

In the SIREN study, a large cohort of healthcare workers are tested regularly by PCR to detect asymptomatic infection in addition to normal testing practices for symptomatic infection. Updated analysis shows the additional incremental benefit from each vaccine exposure including for boosters, even in those who have had prior infection.

Prior infection is 44% effective at preventing future infection, increasing to 71% with 3 doses of the vaccine.

Symptoms
Technical Briefing 34 contains further analysis on symptom comparison on Omicron and Delta.

Of symptomatic cases, loss of smell and taste was found to be more common in people who tested positive for Delta than those who had Omicron. This matches a recent study led by Oxford University and the Office for National Statistics (ONS), using data from the COVID-19 Infection Survey produced by the latter.

Hospital admissions in children aged 0 to 5
There are indications of a small rise in children admitted to hospital, but these early signals need further investigations before we can draw any conclusions about whether Omicron causes more severe illness in children.

Early data shows that young children who are hospitalised experience mild illness and are discharged after short stays in hospital. Data continues to show COVID-19 poses a very low health risk to children and infants.

However, any stay in hospital for a child is too long if you’re a parent and it’s important we all take precautions to avoid the spread of infection.

Follow the latest self-isolation rules if you develop symptoms – wear a mask where required to do so, take regular LFD tests and observe good hand hygiene.

We continue to urge everyone who is eligible to get a COVID-19 vaccine and booster.