Five points to come out of Tuesday’s Sage meeting on Omicron
TRANSMISSABILITY: With the speed of growth in Omicron cases seen to date, decision makers will need to consider response measures urgently to reduce transmission if the aim is to reduce the likelihood of unsustainable pressure on the NHS.
Early verbal reports indicate that hospitalisations due to Omicron are now increasing in South Africa and the spread of Omicron in the UK appears to be following a similar trajectory to that seen in South Africa.
The doubling time for new Omicron infections is currently around three days and is thought to be no slower than a five-day doubling time.
Very rapid doubling times leading to a large wave would result in significant absences from work.
HOSPITALISATIONS: The overall scale of any wave of hospitalisations without interventions is highly uncertain, but the peak could reach several times the current level.
With 291 Covid-occupied beds in Northern Ireland reported on Thursday, that means there could be up to 900 patients hospitalised with the virus by the peak.
In order to be below this level, there would need to be a very high protection from boosters against Omicron and a small degree of immune escape, Sage has said.
HOW IT COMPARES TO DELTA: Reports of superspreader events around the world, some of which involved Omicron, suggest the danger of airborne transmission of Omicron is greater than with pre-existing variants, such as Delta.
As a result, experts at Sage have said “measures to reduce airborne spread such as ventilation, well-fitting masks and distancing or reduced density of people in indoor environments may be even more important”.
The likelihood of transmission in hospitals is also “likely to be an even greater risk as a result of Omicron”.
Measures will need to be put in place to reduce the risk of healthcare workers becoming infected, while measures in other vulnerable settings such as prisons and care homes should also be considered.
HOW QUICKLY IT CAN INFECT: The generation time for Omicron is not known, but Sage has considered the possibility that it is shorter than Delta, which it said, “would mean that case-based interventions, for example finding and isolating cases through contact tracing, become less effective because people become infectious sooner”.
If this is the case, population-based public health measures, such as face coverings and social distancing, will be even more important than measures that pertain only to those who are confirmed as being infected.
HOW QUICKLY WE NEED TO ACT: Hospital admissions will continue to increase for a number of weeks after measures to reduce transmission are put in place.
“This is due to the lags between measures being introduced, these measures affecting incidence of infections, and then this being reflected in hospitalisations,” said Sage.
The faster the growth in infections at the point measures are introduced, the more admissions will increase in the period between action being taken and the number of admissions being affected.
Sage estimates that with a doubling rate of three days, once hospitalisations begin to increase at a rate similar to that of cases, there could be a 16-fold increase in Covid cases in the system before interventions to slow infections are reflected in Covid inpatients.