Just as we are seeing here in the United States (see CDC Nowcast), in Denmark (see SSI Update), and across much of Europe (see ECDC Risk Analysis), Omicron subvariants BA.4/BA.5 are surging in the UK and today the UKHSA announced that together they are now the dominant variants in the UK.
UKHSA issues COVID-19 vaccination reminder as Omicron BA.4 and BA.5 become dominant in the UK, driving increase in infections
The UK Health Security Agency (UKHSA) is reminding people to ensure their COVID-19 vaccinations are up to date and to continue following COVID-safe behaviours, as latest technical data indicates BA.4 and BA.5 have become dominant in the UK and are driving the recent increase in infections.
The UKHSA’s COVID-19 variant technical briefing 43, published today, includes epidemiological analysis that shows that Omicron BA.4 and BA.5 now make up more than half of new COVID-19 cases in England, accounting for approximately 22% and 39% of cases, respectively.
Omicron BA.4 and Omicron BA.5 were designated as variants of concern on 18 May on the basis of an apparent growth advantage over the previously-dominant Omicron BA.2 variant.
UKHSA’s latest analysis suggests that Omicron BA.5 is growing 35.1% faster than Omicron BA.2, while Omicron BA.4 is growing approximately 19.1% faster. This suggests that BA.5 is likely to become the dominant COVID-19 variant in the UK.
The increasing prevalence of Omicron BA.4 and BA.5 is likely to be a factor in the recent increase in cases seen in the UK and elsewhere, though there is currently no evidence that Omicron BA.4 and BA.5 cause more severe illness than previous variants.
So far, vaccination means that the rise in cases is not translating to a rise in severe illness and deaths. UKHSA scientists are urging anyone who has not had all the vaccines they are eligible for to make sure that they get them as soon as possible.
The UKHSA also released their first updated risk assessment on BA.4/BA.5 since late April (see below), and while there are still many unknowns, of the 4 categories of risk (compared to BA.2), these emerging variants score `Worse' in 2, and equivalent in 1, with insufficient data for the 4th.
Assessment and rationale The risk assessment is presented in comparison to the current predominant variant (BA.2). Red indicates the assessed variant as worse than BA.2 in a characteristic, amber equivalent, green improved. The laboratory data includes published data and data supplied by Variant Technical Group (VTG) members (UKHSA, the Genotype to Phenotype Consortium, Oxford University, the Office for National Statistics and SIREN) which has been reviewed by VTG but is unpublished.
The two `worse than BA.2' categories are:
Overall growth advantage (Confidence High)
Evidence of a growth advantage compared to BA.2 BA.4 and BA.5 are now likely to be dominant in England. There is now an associated overall increase in coronavirus (COVID-19) incidence. The growth advantage is also evident in multiple other countries, including those with prior BA.2 waves similar to the UK
Growth advantage 2: Immune evasion (Confidence Medium)
There is evidence of some antigenic change compared to BA.2, based on laboratory data (moderate confidence); insufficient data to assess vaccine effectiveness
BA.4 and BA.5 are most closely related to BA.2. Structural modelling indicates there is likely to be antigenic change compared to BA.1 and BA.2, which may affect the binding of neutralising antibodies. Neutralisation data from prior Omicron infections (human or hamster) shows neutralisation of BA.4 is substantially reduced using BA.1 antisera but there is a more moderate drop in neutralisation by BA.2 specific antisera.
Sera from triple vaccinees shows similar or lower neutralisation for BA.4 compared to BA.2 or BA.1. Sera from vaccinees with BA.1 or BA.2 breakthrough infections shows better cross reactivity against BA.4, although there is variation in the data. There is evidence from 2 national surveillance studies of ongoing reinfection, including after prior Omicron variant infection.
There is insufficient data for a robust assessment of vaccine effectiveness but in population and survey data there were no early indicators of a large change. The current epidemiological data, whilst incomplete, is consistent with the neutralisation findings.
Infection Severity is currently judged as comparable to BA.2, and there is currently insufficient evidence to rate Growth advantage 1: Transmissibility.
Insufficient data There is no direct data on transmissibility and there is no current ability to measure this directly from surveillance data. Based on data reported to VTG, ACE2 binding is increased for BA.4 and BA.5 compared to prior Omicron variants.
Comparable severity to BA.2 does not mean benign, and given their ability to reinfect persons who have only recently recovered from a COVID infection, these variants will likely drive infection rates - and hospitalizations - higher over the months ahead.
The UKHSA is offering the following advice:
There are simple things you can do in your daily life that will help reduce the spread of COVID-19 and other respiratory infections and protect those at highest risk.
Things you can choose to do are:
- get vaccinated
- let fresh air in if meeting others indoors
- practise good hygiene:wash your hands
- cover your coughs and sneezes
- clean your surroundings frequently
- wear a face covering or a face mask, particularly if you are in crowded and enclosed spaces
