Booster protection fades faster against Omicron than Delta, government scientists say

Health officials already reviewing data on whether fourth jab is needed for older age groups

Samuel Lovett
Science Correspondent
Thursday 23 December 2021 18:27
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Protection against Omicron appears to wane more rapidly than Delta among people who are boosted, government scientists have said – suggesting a fourth jab may soon be needed for older age groups in the population.

The UK Health Security Agency (UKHSA) said it has identified a 15 to 25 per cent faster decline in protection against symptomatic disease for those who have been triple-jabbed for 10 weeks or longer.

However, health officials believe it’s unlikely that these individuals are at a greater risk of severe illness. As a whole, people who catch Omicron are 50 to 70 per cent less likely to need hospital care compared to previous variants, new UKHSA analysis shows.

More data is ultimately needed to determine how long protection lasts against hospitalisation from Omicron. This will then shape the decision if, and when, to roll out a fourth jab among people with waning immunity, said Dr Mary Ramsay, head of immunisation at UKHSA.

“We would not rush into changing policy on vaccination until we have more idea about whether or not the protection against severe disease was affected as much [by Omicron],” she added.

“Based on our experience of Delta we saw an effect on vaccine protection against milder disease, but we still saw that the protection against severe disease was sustained. We really need that estimate before we start to worry too much about additional doses.”

However, Dr Susan Hopkins, chief medical adviser at the UKHSA, said it was “important to recognise” that the vast majority of over-60s have had their booster in the last eight to 10 weeks and are therefore not necessarily deemed at risk.

“Our priority is to vaccinate first people who are not vaccinated and then get boosters into as many people as possible.”

The Joint Committee on Vaccination and Immunisation (JCVI) has indicated that it is already reviewing whether a fourth jab will be needed for the over-60s, clinically vulnerable and healthcare workers, after Israel and Germany announced plans to push ahead with the policy.

It’s expected the JCVI and UKHSA will have a “good handle” on which groups are being hospitalised with Omicron in “another couple of weeks”, said Dr Ramsay. “And then of course, we'll look back and see what the other options are.”

In line with two UK studies published on Wednesday, the UKHSA has also concluded that there is a lower risk of hospitalisation for people infected with Omicron compared with Delta.

Analysis of preliminary data showed an individual with Omicron was estimated to be between 31 per cent and 45 per cent less likely to attend hospital, and 50 to 70 per cent less likely to be admitted.

These findings are based on all cases of Omicron and Delta reported in the UK since the beginning of November, including 132 people admitted to hospital with the new variant. There have also been 14 deaths in people within 28 days of catching Omicron.

However, as other scientists have already warned, the apparent reduction in severity could be cancelled out by the rapid spread of Omicron throughout the UK, with 119,789 cases reported on Thursday – another pandemic record.

Dr Jenny Harries, the chief executive of the UKHSA, said: "Our latest analysis shows an encouraging early signal that people who contract the Omicron variant may be at a relatively lower risk of hospitalisation than those who contract other variants.

“Cases are currently very high in the UK, and even a relatively low proportion requiring hospitalisation could result in a significant number of people becoming seriously ill.”

Scientific advisers to the government have warned that Omicron would need to be about 90 per cent less severe than Delta to avoid a winter surge in hospital admissions that reaches the same heights of previous Covid waves.

This estimate is made on the assumption that there will be no further restrictions or “significant” changes in behaviour among the population during the mounting rise in infections, the government’s Scientific Advisory Group for Emergencies said in a meeting held on Sunday.

It ultimately remains unclear if Omicron is innately less virulent than previous variants, or whether it appears so because of the high levels of immunity in the population.

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