Covid cases appear to be rising in older people as increased socialising, waning immunity and a more transmissible version of the Omicron variant threaten to fuel a resurgence of the virus.
Tests on nearly 100,000 swabs from homes across England reveal that, while infections have fallen overall since the January peak, one in 35 people tested positive between 8 February and 1 March, with cases either level or rising in those aged 55 and over.
Scientists on Imperial College’s React-1 study said the R value – the average number of people an infected person passes the virus to – remained below 1 for those aged 54 and under, meaning cases were in decline. But for those aged 55 and over, R stood at 1.04.
The suspected uptick has raised concerns as older people are more prone to severe Covid and have had more time for their immunity to wane, as many had their booster vaccines several months ago.
The findings come as the latest government figures showed a sharp 46% rise in new recorded UK cases week on week – to 346,059 over the past week – and a 12% rise in hospitalisations to 8,950.
Prof Paul Elliott, director of the React study, said the rise was probably driven by factors including the lifting of all Covid legal restrictions in England on 24 February, more mixing between age groups and waning protection from booster shots.
One idea experts are investigating is whether hospitalisation rates are being driven by “unshielding”, where people who have been extremely careful for two years have emerged into a world where infections are still rife.
Another driver is thought to be the BA.2 form of Omicron, a relative of the original BA.1. While BA.2 does not seem to evade immunity any more than BA.1 or cause more severe disease, it spreads faster and increases R by 0.4 compared with BA.1, the Imperial researchers found. “From what we see, BA.2 is more transmissible and may prolong the Omicron wave of the pandemic,” Elliott said. “It’s taking over, so that could explain higher infection rates.”
Since the first BA.2 cases were discovered in December, it has steadily gained ground and now accounts for about half of all Omicron cases in England, with levels currently highest in London. It is unclear how large a wave of infections and hospitalisations BA.2 could drive given widespread immunity from vaccines and past Covid infections.
A further push on vaccinations is due in early April when over-75s and the clinically vulnerable will be offered a fourth shot, or a fifth in the case of people with severely weakened immune systems. “Additional doses of vaccine are almost certainly going to be necessary,” said Prof Peter Openshaw, a member of the government’s New and Emerging Respiratory Virus Threats Advisory Group (Nervtag).
Mark Woolhouse, professor of infectious disease epidemiology at the University of Edinburgh, said it was “impossible to make a sensible prediction” about the size of any BA.2 wave but the situation needed close monitoring. “The worry is that it’s hard to see anything happening in the next few weeks that will reverse the growth of BA.2 unless, that is, people decide on their own account to step up precautions.”
Danny Altmann, professor of immunology at Imperial College, who is not on the React-1 study, said the recent rise was foreseeable. “We’ll see a great deal more of this, along the lines of recent resurgent spikes in Scotland and Hong Kong,” he said. “Caseloads were by no means low or under control as we came out of all mitigations and, when you add in waning immunity and the enhanced transmissibility of BA.2, it looks like we are in for a difficult period, especially for the elderly.”
He said a lack of measures such as mask-wearing and testing potentially left only the option of “a wider push for fourth shots, beyond the over-75s” but cautioned that very regular boosters may not be sustainable long-term.
Openshaw said the rise in cases and hospitalisations should remind people the pandemic is not over. “I think it’s a shame that the message that seems to have got out to the population is that it’s all over and we don’t need to be cautious any more,” he said.