Scientists welcome omicron severity data but warn time will tell

Scientists have said the initial data from the UK’s Health Security Agency (HSA) is encouraging but that the booster vaccine programme will be pivotal in the fight to control the impact of the disease.

In its latest technical briefing the HAS said omicron continues to grow rapidly in all regions of England, however, none of the cases to date is known to have been hospitalised or died.

“Studies of contacts show that Omicron is transmitting more effectively than Delta,” it said. “The UK Health Security Agency (UKHSA) estimates that if omicron continues to grow at the present rate, the variant will become the dominant strain, accounting for more than 50% of all COVID-19 infections in the UK by mid-December. It is projected that if current trends continue unchanged, the UK will exceed one million infections by the end of this month.”

Dr Clive Dix, former chair of the UK Vaccine Taskforce, said: “UKHSA data is early but encouraging and gives confidence that omicron is less virulent (low numbers but no hospitalisations).  All data is trending toward omicron taking over from Delta with less severe consequences so good news.  UK elderly and vulnerable being boosted means UK will be ok.”

Prof Paul Hunter, Professor in Medicine, UEA, said: “The technical briefing from UK HSA summarises what is currently known about omicron in the UK,” said Prof Paul Hunter, Professor in Medicine, UEA.  “Although it is still early days here so that this information is subject to change, especially because of small numbers so far estimates have wide confidence intervals.  Key points include:

“1. Omicron is indeed very infectious and seems to be spreading more rapidly in the UK than in South Africa.  In South Africa the latest R estimate is about 2.2.  For the UK the estimate is 3.7 which is doubling every 2 to 3 days.  I would add that early estimates of R in an epidemic tend to decline over a few weeks so this rate may not be maintained for very long.  But even so an R value in this region would mean that even very strict controls like we have earlier this year may not be sufficient to bring R to below 1.0 and reverse the increase.

“2. The results from household studies suggest transmission of omicron between people who live in the same household is about 3.2 times greater than for delta as would be expected from the above R estimate.

“3. Although transmission in non-household settings is still greater for omicron than for delta, the elevated risk of transmission for omicron compared to delta may be less marked for non-household contracts than for household contracts, but confidence intervals are very wide so shouldn’t read too much into that at present.

“4. The effectiveness of two doses of vaccine against omicron is poor.  A primary course of Pfizer gives only about 35% protection against symptomatic illness from 25 weeks after second dose and AstraZeneca hardly any, though confidence intervals are wide due to small numbers.  But a booster after either primary course gives protection against symptomatic infection in the 70 to 80% range – very reassuring especially as we have done pretty well at rolling out booster to our more vulnerable people.  But it is too early to estimate impact on severe disease, though with this data I think we can realistically expect booster doses to give very good protection against severe disease, possibly in the 90% range.

“5. Following similar reports from South Africa, omicron is far more likely to cause reinfections (an infection is someone who has a history of having had covid previously) by about 5 fold.

“Overall this data confirms the much greater transmissibility of omicron but we have increasing evidence that the booster dose will go a long way to reduce the burden of severe disease over coming weeks.  Despite my suggestion even strict lockdown may not be sufficient to reverse the current growth in omicron, I do not think this mean we should go to a strict lockdown.  If the spread of omicron is inevitable the most important things we can do is ensure continuing rollout of booster and targeted rapid distribution of antivirals to vulnerable individuals early after diagnosis.”

Dr Julian Tang, Honorary Associate Professor/Clinical Virologist, Respiratory Sciences, University of Leicester, added it remains a question of time before the medical community will have the data to make informed decisions.

“Qualitatively – the message on controlling the spread of omicron is similar to delta – get vaccinated and/or boosted, wear masks in indoor crowded areas and public transport, avoid too much social contact if possible, open windows to enhance ventilation if sharing airspace with strangers, etc,” he explained. “Quantitatively – to reduce the impending spread of omicron, we just need to do this faster with higher compliance, to reduce any potential future burden on the NHS – if omicron is of comparable clinical severity to delta.

“The number and position of the S gene mutations in omicron do not make its vaccine escape capabilities very surprising – but they will still likely offer protection against severe disease and death.

“However, I am hoping that this will be balanced by a milder and more typical flu-like illness clinical profile. Time will tell.”

Follow us on twitter: @risksEmerging

Twitter feed is not available at the moment.