The new BA.2 coronavirus subvariant is one and a half times more infectious than the original Omicron strain, the Danish State Serum Institute (SSI) has said. At the same time, the initial analysis by the institute showed no difference in the risk of hospitalization with BA.2 compared with BA.1.
Scientists say the Omicron BA.2 sub-variant is 1.5 times more contagious than the current dominant strain in many parts of the world.
The new strain of coronavirus has already become dominant in Denmark, and the country’s main infectious disease body, the Statens Serum Institut (SSI), said preliminary calculations show BA.2 could be one and a half times more infectious than its predecessor. BA.1, which currently accounts for the majority of cases in Britain.
However, the initial analysis by the Danish Institute showed no difference in the risk of hospitalization with BA.2 compared with BA.1.
“There are some indications that it is more contagious, especially for the unvaccinated, but it can also infect people who have been more vaccinated,” SSI CTO Tyra Grove Krause said at a briefing.
The new variant of the virus is currently circulating and more than half of the US states have at least 127 known cases nationwide, the Centers for Disease Control and Protection (CDC) said.
A UK Health Security Agency (UKHSA) report says that by January 16, the new Omicron strain accounted for 3.4% of new infections in England, and the numbers are doubling every week.
Scientists believe the new sub-variant may have evolved to be slightly more contagious than its ancestral Omicron strain, and it may gradually become the dominant COVID virus. It is already outperforming its parent variant in Denmark, but the Scandinavian country’s government has deemed the strain harmless and this week announced the lifting of all coronavirus-related restrictions.
And Professor Paul Hunter, an epidemiologist at the University of East Anglia, told MailOnline that there was no reason to panic about BA.2. He said the strain does not cause “a significant difference to our current threat assessments.”
Last week, the BA.2 strain was recognized as an investigational variant, and on Friday the UKHSA reported that as of January 24, 1,072 confirmed cases had been identified in England. The agency said that BA.2 has a higher growth rate compared to BA.1 in all regions of England where there were enough cases to evaluate it. It added that while the growth rate may be inflated by early analysis of the new option, “the clear benefit of growth is currently significant.”
Contact tracing analysis indicates that between December 27 and January 11, transmission was likely higher among contacts with household BA.2 cases (13.4%) than among contacts with other Omicron cases (10.3 %). But the agency warned that the results should be interpreted with caution as early results can change quickly as new options are identified. The preliminary evaluation found no evidence that vaccines would be less effective against symptomatic disease BA.2. There is currently no data on the severity of the strain.
Dr Susan Hopkins, UKHSA Chief Medical Officer, says: “We now know that BA.2 has an increased growth rate that can be seen in all regions of England. We also learned that BA.2 has a slightly higher rate of secondary attacks than BA.1 in households. While the number of hospitalizations and deaths remains low, the number of cases is still high in some areas and in some age groups, so it is important that we continue to act cautiously as restrictions are lifted. Consider wearing a face mask in public places. Get vaccinated to protect yourself from COVID-19. If you have any symptoms, get tested.”
The UKHSA also published an analysis of the original Omicron BA.1 strain. Where variant information was available, the majority of intensive care unit (ICU) admissions from November 24 last year to January 19, 2022 were for the Delta variant of the coronavirus. The data also suggests that overall ICU admissions have decreased over time, but where Omicron admission data were available, they increased from 9% to over 50% in the last week.
Although nursing homes saw a rapid rise in infections in December, there was no associated increase in hospital admissions, according to the UKHSA.
The UKHSA said the results show the current wave of Omicron infections is unlikely to result in a major spike in severe illness in nursing homes with high vaccination coverage and/or natural immunity. It is also stated that the amount of BA.2 in this study was limited, and no conclusions can be drawn regarding the strain.
Jonathan Ball, professor of molecular virology at the University of Nottingham, says: “Evidence to date suggests that BA.2 may be more transmissible than its close relative Omicron. However, key questions are whether this variant is associated with more severe disease and whether it can escape the immunity provided by vaccines. Preliminary evidence suggests that the vaccines will provide the same levels of protection as Omicron, so that’s good news. Whether this causes more severe illness will become clear as more data is collected.”