APPARENTLY THE BRITS DO NOT AGREE:
British experts called into question the claims made by the department, saying that if this was the case then Covid infections in the UK would not have dipped.
www.dailymail.co.uk
(fair use applies)
Why the Delta Covid variant ISN'T really spreading as quickly as chickenpox (even though US health officials say the mutant strain is just as contagious)
By Luke Andrews
Published: 11:50 EDT, 30 July 2021 | Updated: 13:40 EDT, 30 July 2021
- CDC officials have claimed the Indian 'Delta' variant may be as infectious as chickenpox
- But British scientists have today slammed the claim as not 'plausible' because of falling infections in the UK
- They point to the vaccination drive leaving enough people with immunity to limit the spread of the virus
Top scientists today claimed the Indian 'Delta' variant is not spreading as quickly as chickenpox, despite US health officials saying it is just as contagious.
Data circulating within America's Centers for Disease Control and Prevention (CDC) claimed people infected with the mutant strain can go on to infect eight others.
The same internal document also alleged that fully-vaccinated people can spread the Indian variant just as easily as unvaccinated people because they carry a similar amount of the virus in their nose and mouth.
Dr Rochelle Walensky, the director of the CDC, insisted the agency was 'not crying wolf', saying the situation was 'serious' and that the measures needed to tackle the spread of Delta were 'extreme'.
But British scientists have questioned some of the claims made by the department, which has urged Americans to keep their coverings on indoors regardless of whether they've been vaccinated or not.
Professor David Livermore, an infectious diseases expert from the University of East Anglia, said vaccine-triggered immunity and the endless waves of Covid which nations have endured meant there were fewer susceptible people around for people to infect.
'The US, like the UK, has substantial immunity from prior infection and from vaccination,' he told MailOnline. 'This will surely be a major drag on Delta's spread, precluding (viral spread) numbers of that magnitude.'
And Professor Julian Tang, a virologist at Leicester University, said the theory was likely just 'speculation' because it was very difficult to track down the number of cases sparked by a single infection.
This graph shows how many people someone infected with the above diseases is likely to transfer them on to. For people who catch chickenpox, scientists estimate they will pass on the infection to between 10 and 12 others. And for those who catch measles, they are thought to pass it on to 12 to 18 others. Scientists at the CDC have estimated every person who catches the Indian 'Delta' variant of Covid could pass it on to eight other people. But British scientists say this is not correct
The R0 — the basic reproduction rate which shows just how contagious every disease is — of Delta is thought to be around eight, the CDC says.
That means, in theory, anyone infected with the mutant strain — which is now dominant in dozens of countries — will pass it on to eight others.
For comparison, the original strain of Covid that triggered the pandemic in the Chinese city of Wuhan had a figure of around 2.5. The Kent 'Alpha' variant's rate is around 4.5.
But measles — which is one of the most contagious viruses known to exist — has an R0 of approximately 18, and the estimate for chickenpox sits between 10 and 12.
This does not mean, however, that everyone infected with Delta is actually passing the virus on to eight others.
The actual R rate — which reflects how quickly an outbreak is growing or shrinking — is always much lower than R0.
This is because it takes into account real-world data which can easily skew the shape of disease outbreaks, such as population immunity.
Professor Livermore said if everyone with Delta was really spreading it to eight others, then Britain's daily Covid cases would not have dipped.
'I don’t find it plausible,' he told MailOnline when asked whether infected patients were truly passing the virus on to so many other people.
'Were it the case, the rise in the UK wouldn’t have stalled in the way that it has.'
Professor Tang said the R0 value was very hard to work out because it was so difficult to establish exactly how many people an infected person passed the virus on to.
He added, in some cases, the virus may spread to many others by one person because of factors including location, but that in other cases someone may not even pass the virus to anyone.
Professor Tang said: 'If you have someone infected and handing out leaflets by the door of a department store they may not be a super-spreader themselves but just passing it on.
'But if you stand them near a fan you may find there is an R of 20.'
The CDC's claim is partially based on an outbreak in Provincetown, Massachusetts, which sparked more than 700 cases.
Leaked slides published by the Washington Post said it happened after July 4 Independence Day, when looser restrictions again allowed Americans to come together to celebrate the national holiday.
Covid finds it easier to spread when people are packed together inside, such as for celebrations and events.
The CDC also claimed that vaccinated people may pass on the virus as well as those who are not jabbed at all because they had similar amounts of the virus in their mouths and noses.
The amount of virus an infected person is carrying is calculated as the Ct value, or the number of times testers need to tweak a sample before they detect the virus. For this reason, a lower score indicates a higher viral load, making it more likely someone is infectious.
Among the 80 double-vaccinated people they checked they had to run the cycle 21.9 times on average before Covid was spotted.
And among the 65 un-vaccinated people included in the study the cycle had to be run 21.5 times.
British Government officials warn Ct values are only approximate, and can even vary if the same swab is tested twice meaning it is hard to make firm conclusions from the data.
But the officials said if the virus is detected after less than 30 tweaks of the sample, then it suggests the infected patient is carrying a lot of virus.
Samples are generally tweaked up to 40 times before someone can be said not to be infected with the virus.
Professor Young said it was 'hard to believe' vaccinated people would pass on the virus as well because the jabs slash the risk of someone becoming infected.
Professor Young said it was still clearly sensible to wear masks — even if you are double-jabbed — to limit your risk of catching the virus.
'Face masks are something I think we still need to be doing,' he said. 'A small proportion of people who are jabbed are still able to get re-infected, so people should be cautious.'
Although vaccines are not perfect, they have drastically changed the game against the virus.
Jabs currently being deployed in America and Britain slash the risk of death by up to 95 per cent, even against the Delta variant.
But real-world data of roll-outs in countries where the mutant strain is dominant show they are slightly less effective at blocking symptoms of the illness, as well as transmission.
Yet No10's top scientists have still publicly backed their ability at curbing the spread of the virus.
Sir Patrick Vallance, the UK Government's chief scientific adviser, said in January: 'You don't have vaccines of this efficacy without there being some effect on transmission.' The latest SAGE modelling given to ministers suggests the vaccines cut the risk of infected people passing it on by around 50 per cent.
Dr Walensky said yesterday the Delta variant was 'one of the most transmissible viruses we know about'. She drew a comparison between the virus and measles and chickenpox, which are both highly contagious.
She also called for masks to be worn again. 'The measures we need to get this under control — they're extreme,' Dr Walensky said. 'The measures you need are extreme.'
The CDC said in May that fully vaccinated people no longer needed to wear face coverings because of falling infection rates and the fact jabs significantly cut the risk of being infected.
But they rowed back on this assertion two days ago, urging fully-vaccinated Americans to again wear the masks amid surging cases in the country and concern over the Delta variant.
The CDC report also claimed vaccinated people who are infected with Covid are likely to shed as much Covid as people who have not been jabbed.
Dr Walter Orenstein, who heads the Emory Vaccine Centre in the US, told CNN the report suggests vaccinated and un-vaccinated people have similar viral loads.
He said: 'The bottom line is, in contrast to the other variants, vaccinated people, even if they don't get sick, got infected and shed the virus at similar levels to unvaccinated people who got infected.'
But he also pointed to data from the CDC showing vaccines cut the risk of severe disease by 90 per cent, and reduce the risk of death by tenfold.
Professor Ian Jones, a vaccine expert at Reading University, said: 'The issue in the US is that there is still a large pool of unvaccinated people so any transmission finds them and they suffer the full range of symptoms.
'Every variant to date has transmitted better, that's why they succeed in spreading, but none have evaded the immune response completely.
'Mask wearing and other social measures continue to make sense while there is a susceptible population but the overall message dose not change, increasing vaccine coverage is the way to bring cases down.'
~~~~~~~~~
What does the CDC claim in its latest report?
Leaked slides from a presentation by the US-based Center for Disease Control and Prevention have made several claims about the Indian 'Delta' variant of Covid.
Its director, Dr Rochelle Walensky, said they highlighted how 'serious' the situation had become.
Below, MailOnline has gone through the key claims.
Indian 'Delta' variant of Covid is as infectious as chickenpox
The R0 — the basic reproduction rate which shows just how contagious every disease is — of Delta is thought to be around eight, the CDC says.
That means, in theory, anyone infected with the mutant strain — which is now dominant in dozens of countries — will pass it on to eight others.
For comparison, the original strain of Covid that triggered the pandemic in the Chinese city of Wuhan had a figure of around 2.5. The Kent 'Alpha' variant's rate is around 4.5.
But measles — which is one of the most contagious viruses known to exist — has an R0 of approximately 18, and the estimate for chickenpox sits between 10 and 12.
This does not mean, however, that everyone infected with Delta is actually passing the virus on to eight others.
The actual R rate — which reflects how quickly an outbreak is growing or shrinking — is always much lower than R0.
This is because it takes into account real-world data which can easily skew the shape of disease outbreaks, such as population immunity.
Infected vaccinated people may pass on the virus 'as well' as un-vaccinated people
The CDC also claimed in its internal presentation that vaccinated people may pass on the virus just as well as those who are not jabbed.
It based the claim on a study looking into how much of the virus is carried by infected jabbed and non-jabbed people.
This is called the viral load and it is tested using the Ct value, the number of times a swab for SARS-CoV-2 must be tweaked before the virus is detected. For this reason, a lower score indicates a higher viral load which suggests someone is more infectious.
The claim was based on an outbreak in Provincetown, Massachusetts, which sparked more than 700 cases.
The outbreak happened after July 4 Independence Day, when looser restrictions again allowed Americans to come together to celebrate the national holiday.
Testing data showed among the 80 double-vaccinated people, their average Ct scores was 21.9.
And among the 65 un-vaccinated people included in the study it was 21.5.
Studies warn Ct values are only approximate, and can vary even if the same swab is tested twice.
But studies say a result above 30 suggests a high amount of the virus in someone's body, and that someone can only be declared negative if the samples are tweaked 40 times without the virus being detected.
British experts said it was highly unlikely that vaccinated people were as infectious as unvaccinated people.
One said the results may be down to there being fewer vaccinated people in America, giving the virus more opportunities to spread.