European countries are seeing a significant increase in Covid-19 cases spurred by highly infectious subvariants of Omicron, raising fears of a new global wave of the disease as immunity declines and the summer travel season gets underway.
The European Centre for Disease Prevention and Control (ECDC) warned last week that "the growth advantage reported for BA.4 and BA.5 suggest that these variants will become dominant" throughout the European Union, and probably result in a surge in cases.
New studies have shown that Omicron subvariants BA.4 and BA.5 have a growth advantage compared with earlier variants and appear to be good at evading the immune system. In other words, neither previous infections nor vaccines provide particularly strong protection against the subvariants, which is why they're becoming the dominant strains. BA.4 and BA.5 do not appear to lead to more severe illness, but, as with previous waves, the increase in cases could result in an uptick in hospitalizations and deaths, the ECDC has said.
The potential impact of one of the subvariants, BA.5, is most apparent in Portugal, where it has fueled a significant rise in Covid-19 infections. That surge now appears to have plateaued, but is still higher than rates elsewhere. On Tuesday, the country registered a daily average of 1,332 new cases per million people over the previous seven days — the fifth-highest new case rate in the world. That compares with Germany's 760 and France's 747, according to OWID.
The number of people in hospital in Portugal, at 1,896, is nearly as high as it was during the original Omicron wave in January. BA.5 became the dominant strain in the country in May, not long after it was first detected in late March, according to Portugal's National Institute of Health (INSA). By June 5, it accounted for 84% of all Covid infections there.
In France, the number of new cases per million people has nearly tripled since the beginning of the month, and hospitalizations are rising for the first time since the beginning of April. According to the public health agency Santé Publique France, in its most recent update, BA.5 rose to 24% of sequenced cases in the week of June 6, compared with 18% the week before.
French vaccination chief Alain Fischer said on Wednesday that the question wasn't whether the country was facing a new wave of the virus, but what intensity it might have, saying he was personally in favor of reinstating some restrictions to limit the spread.
"With the new Omicron subvariants (BA.4 and BA.5), which are 10% to 15% more contagious, the epidemic has found new energy, even though we have passed through the winter," Davido said, adding that the lifting of almost all restrictions — like wearing masks on public transportation and airplanes — combined with unraveling immunity, posed a real threat.
Davido and other health experts have warned that hospitals in France could fill up over the summer, unless vulnerable people and those over 60 get booster shots as soon as possible. But while hospital admissions in the country are on the rise, it's not yet clear whether that's down to the BA.5 subvariant being more transmissible or because it is escaping dwindling immunity.
In the UK, where cases and hospitalizations are rising sharply, the start of a new wave also appears to be driven by BA.4 and BA.5, according to the Office for National Statistics (ONS). The latest data from the ONS, released on June 17, showed that Covid infections were up 43% week on week, according to the British Medical Journal (BMJ), a peer-reviewed medical trade journal.
Writing in the BMJ, Christina Pagel, professor of operational research at University College London, said, "We will be the first (but not the last) major country to have a BA.4.5 wave after having had two previous Omicron waves. This means that we might get some additional protection from the high number of infections we had in March which will reduce the size of this coming wave. Nonetheless, a significant proportion of the country will get sick, especially as boosters are waning."
It looks like the United States might not be far behind. The latest data from the US Centers for Disease Control and Prevention (CDC) shows BA.4 and BA.5 caused more than one in three Covid-19 infections in America last week. The subvariants are also expected to dominate transmissions in the US within the next few weeks.