The document from the Centers for Disease Control and Prevention (CDC), obtained by The Washington Post, described the Delta strain as “a variant so contagious that it acts almost like a different novel virus”.
It said that Delta, which was first identified in India last year, leaps from target to target more swiftly than even Ebola or the common cold.
But the variant is roughly as deadly as the ancestral strain, whereas SARS, Ebola and other diseases had far higher fatality rates, the report showed.
The more worrying highlight of the document is perhaps the Delta variant’s effect on individuals who are vaccinated.
According to the report, the document cited a combination of recently-obtained unpublished data which showed that vaccinated people infected with Delta have measurable viral loads similar to those who are unvaccinated and infected with the variant.
The studies revealed that vaccinated individuals infected with Delta may be able to transmit the virus as easily as those who are unvaccinated.
One of the slides stated that there is a higher risk among older age groups for hospitalisation and death relative to younger people, regardless of vaccination status.
CDC director Dr Rochelle P Walensky had acknowledged on Tuesday that vaccinated people with so-called breakthrough infections of the Delta variant carry just as much virus in the nose and throat as unvaccinated people and may spread it just as readily, if less often.
Walensky told CNN that the Delta variant “is one of the most transmissible viruses we know about. Measles, chickenpox, this — they’re all up there.”
“The measures we need to get this under control — they’re extreme. The measures you need are extreme,” Walensky said.
“The bottom line was that, in contrast to the other variants, vaccinated people, even if they didn’t get sick, got infected and shed virus at similar levels as unvaccinated people who got infected,” Walter Orenstein, who heads the Emory Vaccine Center and who viewed the documents, told CNN.
‘Vaccinated people safer’
On the brighter side, the document indicated that vaccinated people are comparatively safer when it comes to developing a severe form of the disease despite being as susceptible to catching the infection as the unvaccinated.
“Vaccines prevent more than 90 per cent of severe disease, but may be less effective at preventing infection or transmission,” it said.
“Therefore, more breakthrough and more community spread despite vaccination,” the document added.
The document said the immediate next step for the CDC is to “acknowledge the war has changed” and improve the public’s understanding of breakthrough infections as well as the big reduction in the risk of severe disease for vaccinated people, the document said.
Delta’s global march
The report comes at a time when several countries worldwide are already grappling with a fresh round of infections fueled primarily by the Delta variant.
US, UK, Israel, Australia, Japan, Indonesia, Bangladesh, along with several other European and Asian countries are witnessing a sharp rise in cases with the variant spreading rapidly in the community.
Australia has called in the military to help enforce isolation in the hard-city of Sydney which has reported a steep surge in infections.
China, where the virus first originated, is also battling its worst outbreak in months caused by Delta variant-fuelled surge. A cluster of infections in Nanjing city linked to airport workers who cleaned a plane from Russia earlier this month had reached the capital Beijing and five provinces by Friday.
The United States has ramped up efforts to get people vaccinated in the face of a Delta variant-fueled surge.
The surge across America — which has the highest known Covid-19 death toll in the world — has left early vaccine adopters angry at those who have so far opted against the shot.
Japan has expanded a coronavirus state of emergency to four more areas in addition to Tokyo following Delta-fueled record spikes in infections as the capital Tokyo hosts the Olympics.
The World Health Organisation recently said the variant is also driving a fourth wave in the middle east region, where rate of vaccination is poor.
(With inputs from agencies)