27, August 2021
Covid-19: Has Delta killed the herd immunity dream? 0
As the Delta variant continues its global surge, experts are questioning whether the long-held goal of achieving herd immunity from Covid-19 through vaccination is still viable.
Herd immunity is achieved when a certain threshold of the global population has either been inoculated against a pathogen or has recovered from infection.
But whether or not it is achievable with Covid-19, with the regular emergence of more infectious strains, is up for debate.
“If the question is ‘will vaccination alone allow us to dampen and control the pandemic?’ the answer is: no,” epidemiologist Mircea Sofonea told AFP.
He said herd immunity hinged on two basic factors.
“That’s the intrinsic infectiousness of the virus and the efficacy of vaccines to protect against infection. And at the moment, that efficacy isn’t there.”
Delta has shown to be roughly 60 percent more transmissible than the Alpha variant of the SARS-CoV-2 virus, and up to twice as infectious as the original strain that emerged in late 2019.
The more effective the virus becomes at infecting people, the higher the herd immunity threshold becomes.
“Theoretically, it’s a very simple calculation to make,” said epidemiologist Antoine Flahault.
For the original virus, which had a reproduction rate between zero and three — meaning each infected person infects up to three others — herd immunity could have been achieved with around 66 percent of people immunised, Flahault told AFP.
“But if the reproduction rate is eight, as with Delta, that puts us closer to 90 percent,” he said.
Were vaccines 100 percent effective at stopping Delta infections, that 90 percent could conceivably be possible. Unfortunately, they aren’t.
– Waning immunity? –
According to data published this week by US authorities, the efficacy of the Pfizer and Moderna mRNA vaccines at preventing infection has fallen from 91 percent to 66 percent since Delta became the dominant variant.
And studies have shown that the vaccine efficacy against infection with Delta falls over time — one of the reasons why several countries are now readying for an autumn third shot, or “booster”, vaccination campaign.
With all this taken into account, absent other health measures such as mask-wearing or social distancing, Sofonea said it would take more than 100 percent of people to be vaccinated in order to guarantee transmissions end — an obvious impossibility.
“The Delta variant will still infect people who have been vaccinated and that does mean that anyone who’s still unvaccinated, at some point, will meet the virus,” Andrew Pollard, director of Britain’s Oxford Vaccine Group, told lawmakers this month.
– ‘Mythical’ –
But even if, as Pollard termed it, the “mythical” aim of herd immunity is no longer in play, experts stressed that getting vaccinated remained paramount.
As with vaccines against other, now-endemic diseases such as measles and influenza, the Covid vaccines offer excellent protection against severe illness.
“What scientists are recommending is to get the maximum number of people protected” through vaccination, said Flahault.
Eventually, of course, all pandemics end.
Sofonea said it would still be possible that Covid would become another endemic disease over time, “just not with vaccines alone”.
He envisioned a near future where “masks and social distancing continue in certain regions” in order to limit transmission and, ultimately, severe illness.
“During the AIDS pandemic, when scientists said we needed to wear condoms, lots of people said: ‘OK, we’ll do it for a while’,” said Flahault.
“And in the end they kept on using them. It could well be that we will continue using masks in enclosed spaces and on transport for quite some time.”
Source: AFP
27, August 2021
Ronaldo misses Juve training as Man City rumours rumble 0
Cristiano Ronaldo will not train with Juventus on Friday, the Serie A giants confirmed to AFP, as rumours of an imminent move to Manchester City gather pace.
Widespread media reports said that Ronaldo left Juve’s Continassa training centre before the start of Friday’s session. Sky Sport Italia reported that the five-time Ballon d’Or winner arrived in the morning to say goodbye to his teammates before leaving at around 10:45 am local time (0845 GMT).
Asked by AFP if Ronaldo would be training with his Juve teammates, a club spokeswoman confirmed that he would not.
According to daily Gazzetta Dello Sport, a deal for superstar Ronaldo to go to Premier League champions Manchester City could be completed with the next 24 hours.
Despite Juventus insisting the 36-year-old was staying, on Thursday Sky claimed the Portugal captain had already cleaned out his locker in the dressing room and is reluctant to make himself available to face Empoli this weekend.
If a deal is to be reached, the clock is ticking with the transfer window set to close on Tuesday.
Premier League champions City have been widely linked with a move for the five-time Ballon d’Or winner after missing out on England captain Harry Kane.
The fee, however, could be a problem with the Italians believed to be wanting in the region of 25 million euros ($29.4 million).
Ronaldo, who has one year remaining on his contract, has also been linked with Paris Saint-Germain and a return to Madrid.
Ronaldo joined Juve in 2018 to huge fanfare.
Last weekend, Juventus coach Massimiliano Allegri insisted that he had received assurances from the Portugal star over his future.
“Let’s clarify this issue, Ronaldo told me that he’s staying,” Allegri said in response to numerous questions on Ronaldo’s form and mindset ahead of Sunday’s Serie A opener at Udinese.
“He has always trained well and has always been available. I’ve read rumours in the papers, but he’s never wanted to leave Juventus.”
Italy’s top scorer last season with 29 goals started the Udinese game on the bench.
– ‘Disrespectful’ rumours –
Last week, Ronaldo himself rubbished reports of a move back to Real Madrid, calling them “disrespectful” and saying that stories of his departure were written with “nobody ever being concerned about trying to find out the actual truth”.
Real have since had an initial bid of 160 million euros for PSG star Kylian Mbappe rejected, but according to French media reports are set to make a second offer of 180 million.
That would close any route for Ronaldo back to the Santiago Bernabeu, although as well as the reports of a possible move to City, there have also been rumours he could join old rival Lionel Messi in Paris to replace Mbappe should the Frenchman leave.
Ronaldo scored 118 goals in 292 appearances for Manchester United early in his career before leaving for Madrid in 2009.
He joined Juve in 2018 after scoring a remarkable 450 goals in 438 matches in a glittering nine-year spell at the Bernabeu that also included four Champions League triumphs.
At Juventus, his hopes of winning another Champions League have been thwarted, with the club failing to get beyond the quarter-finals during his time in Turin.
Last season, they were deposed as Italian champions by Inter Milan.
Source: AFP