UK Covid rise as Stratus and Nimbus dominate, booster rules narrowed

Cases of Covid-19 in the United Kingdom have increased in recent weeks, circulating at what public health officials describe as medium levels, and two recently identified strains are now the most prevalent, according to government surveillance data for the week ending October 12. Health authorities are urging people who meet the revised eligibility criteria for the autumn vaccine to book their booster, while changes to those criteria have prompted confusion about who can receive a free jab on the NHS.

The UK Health Security Agency reported an uptick in Covid activity in its latest weekly data, including a rise in the proportion of positive tests among people in hospital settings, which increased to 12.9 per 1000 tested from 11.7 the previous week. Two lineages, XFG and NB.1.8.1, referred to in some reports as Stratus and Nimbus, are now dominant in circulation. The World Health Organization has listed Stratus as a variant under monitoring. So far, authorities say there is little evidence these strains cause more severe illness than other currently circulating variants.

Clinicians and pharmacy staff have noted differences in early symptoms reported with the new lineages. Some...