European countries are seeing an increase in Covid-19 hospitalizations caused by subvariants of the highly infectious Omicron strain, threatening a new global wave of the disease as immunity levels decline and pandemic restrictions are lifted.
Admissions have increased in several countries including France and England, according to data analyzed by the Financial Times. Omicron’s BA.5 subvariant now accounts for more than 80% of new infections in Portugal. And in Germany, where admissions have been rising for more than a week, the share of Covid-19 infections attributed to BA.5 doubled at the end of last month.
Experts warn that widespread reductions in testing and surveillance could compromise countries’ ability to detect new mutations and respond quickly. They fear this could lead to waves later in the year that will put pressure on health systems and could prove harder to contain.
“We haven’t come out of the woods with this at all. The biggest concern is that we have let our guard down considerably,” said Lawrence Young, a virologist at the University of Warwick in the UK. A key question is how the northern hemisphere will evolve as it enters its winter months, he said, as health systems grapple with seasonal respiratory viruses on top of the probable arrival of new variants.
Piotr Kramarz, head of surveillance at the European Center for Disease Prevention and Control, said Omicron subvariants such as BA.4 and BA.5 have an element of “immune evasion” – meaning that neither previous infections nor vaccines offer such strong protection. – which pushed them to go beyond the previously dominant variants.
Kramarz said BA.4 and BA.5 did not appear to lead to more severe disease, but he warned that those who had the virus before were getting infected again. Triple-pricked people were also getting sick, although evidence suggests vaccines continued to provide strong protection against the worst outcomes.
The potential potency of an Omicron subvariant, BA.5, is clearest in Portugal, where there has been a sharp rise in Covid-19 hospitalizations over the past month, rising almost as high as its original Omicron wave in January and resulting in higher excess mortality – the difference between deaths from all causes during the pandemic and the historical seasonal average. BA.5 quickly became dominant after it was first detected in the country at the end of March, according to the National Institute of Health (INSA). As of June 5, it was estimated to account for 84% of new infections.
In Germany, admissions have risen in the past 10 days after a steady 10-week decline, although current levels remain at about a quarter of the March BA.2 Variant peak, according to FT analysis of hospital data. . BA.5’s share of total infections doubled in the last week of May to 10%.
Hospitalizations in France are rising for the first time since early April and BA.5 rose from 5% to 18% of sequenced cases in the week to May 24, according to public health agency Santé Publique France.
But scientists are still working out the precise cause of the rise in hospital admissions in parts of Europe. “It is very difficult to distinguish whether it is more transmissible or whether it escapes the decreasing immunity of vaccines,” said Antoine Flahault, director of the Institute of Global Health at the University of Geneva.
In England, there were an average of 639 new cases of Covid-19 a day in hospitals last weekend, up 29% from the previous weekend, but still less than a third of the peak of April’s BA.2 wave.
Although the number of admissions continues to rise, there are early indications that week-over-week growth may be slowing. Experts warn it’s too early to say the wave was in remission, but if the downturn continues it would suggest the peak may be near.
Saffron Cordery, acting chief executive of NHS Providers, which represents health trusts across England, noted that vaccinations “still held back the full force of infection” and that there had only been a “tiny increase” in the number of patients requiring ventilation beds.
The new subvariants are also advancing in the United States, where data released by the Centers for Disease Control and Prevention shows that, combined, they accounted for more than 20% of all Covid-19 cases in the week leading up to the June 11. They are, however, arriving on the heels of the wave of US BA.2 variants, making it difficult to disentangle their impact on the overall trend.
Amesh Adalja, a senior researcher at the Johns Hopkins School of Public Health in Baltimore, said BA.5 appeared to be more common in midwestern and southern states. But he suspected that the subvariants would become more dominant in the coming weeks.
Eric Topol, founder and director of the Scripps Research Translational Institute, said BA.4 and BA.5 were markedly different from previous Omicron subvariants, adding that they are “more resistant” to monoclonal antibody therapies, which work by infusing patients with proteins that mimic the body’s immune response.
Without comprehensive vaccine response data, it’s hard to say how much the subvariants would reduce protection against hospitalization, Topol said. He said that while this protection for boosted individuals was around 95% against the Delta strain and 85% for BA.1 or BA.2, levels could drop into the 80s or 70s with the new subvariants.
Despite these concerns about reduced protection, governments do not seem to be considering reintroducing restrictions.
Portugal does not plan to bring back curbs or implement new measures. And German Justice Minister Marco Buschmann has rejected passing new restrictions until the impact of previous ones has been assessed, despite pleas from teachers’ unions to prepare for an autumn wave .
Experts have warned against complacency.
In the United States, Topol said authorities had failed to grasp the threat posed by the subvariants and needed to do more to protect people, including promoting mask-wearing, vaccinations and boosters. “They claim it’s all done – it’s over,” he said. “That couldn’t be further from the truth.”
Additional reporting by Peter Wise in Lisbon, Guy Chazan in Berlin and Akila Quinio in Paris