It spreads like chickenpox, even fully vaccinated not protected, says US study
In what seems to be gloomy prognosis in the fight against Covid-19 pandemic for now, the USA Centers for Disease Control and Prevention (CDC) has warned that the Delta variant of coronavirus is much more contagious, more likely to break through protections afforded by the vaccines, and may cause more severe illness than all other known versions of the virus.
The internal presentation circulated within the US CDC paints a grim picture of what is in store for the future for the world battling the virus. It comes in the wake of a WHO warning that the global number of new coronavirus cases has grown by at least 12 per cent over the past week, with almost all regions reporting a rise in infections.
The new US CDC data suggest that vaccinated people are spreading the virus and contributing to those numbers — although probably to a far lesser degree than the unvaccinated.
Dr Rochelle P Walensky, the director of the CDC agency, 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, according to news reports.
But the internal document lays out a broader and even grimmer view of the variant.
The Delta variant is more transmissible than the viruses that cause MERS, SARS, Ebola, the common cold, the seasonal flu and smallpox, and it is as contagious as chickenpox, according to the document.
The immediate next step for the agency is to “acknowledge the war has changed,” the document said. Its contents were first reported by The Washington Post on Thursday evening.
The document’s tone reflects alarm among CDC scientists about Delta’s spread across the country, said a federal official who has seen the research described in the document.
The agency is expected to publish additional data on the variant on Friday.
“The CDC is very concerned with the data coming in that Delta is a very serious threat that requires action now,” the official said.
Dr Walensky has called transmission by vaccinated people a rare event, but other scientists have suggested it may be more common than once thought.
The agency’s new masking guidelines for vaccinated people, introduced on Tuesday, were based on the information presented in the document. The CDC recommended that vaccinated people wear masks indoors in public settings in communities with high transmission of the virus.
But the internal document hints that even that recommendation may not go far enough. “Given higher transmissibility and current vaccine coverage, universal masking is essential,” the document said.
The agency’s data suggest that people with weak immune systems should wear masks even in places that do not have high transmission of the virus. So should vaccinated Americans who are in contact with young children, older adults, or otherwise vulnerable people.
Infection with the Delta variant produces virus amounts in the airways that are tenfold higher than what is seen in people infected with the Alpha variant, which is also highly contagious, the document noted.
The amount of virus in a person infected with Delta is a thousandfold more than what is seen in people infected with the original version of the virus, according to one recent study.
Detailed analysis of the spread of cases showed that people infected with Delta carry enormous amounts of virus in their nose and throat, regardless of vaccination status, according to the CDC document.
Infection with the Delta variant may be more likely to lead to severe illness, the document noted. Studies from Canada and Scotland found that people infected with the variant are more likely to be hospitalized, while research in Singapore indicated that they are more likely to require oxygen.
Still, the CDC’s figures show that the vaccines are highly effective in preventing serious illness, hospitalization and death in vaccinated people, experts said.