The nation’s top infectious disease expert says the Indian ‘Delta’ Covid variant has the same viral levels in vaccinated people who have breakthrough infections as in those who are unvaccinated.
Dr Anthony Fauci told MSNBC on Wednesday that means vaccinated people can spread Delta and explains why the Centers for Disease Control and Prevention (CDC) backtracked on mask recommendations for those who got their shots.
Previous research has indicated that people infected with Delta have 1,000 times more copies of the coronavirus in their respiratory tracts compared to those infected with older strains of the virus.
But the CDC has yet to publicly share new research on Delta transmission among the vaccinated that would back up its new mask guidance. Outside experts are calling for the agency to show them the data.
Vaccinated people can spread Delta just like unvaccinated people, Dr Fauci says
¿¿¿¿ Dr. Fauci: “La Variante Delta ha cambiado todo” “Cuando se observa el NIVEL de virus en la nasofaringe de una persona vacunada que contrae infección con #Delta, es EXACTAMENTE EL MISMO que el nivel de virus en una persona no vacunada que se infecta.
Ese es el PROBLEMA”@MSNBC pic.twitter.com/vdvs4CvgzB
— ciclbh (@ciclbh) July 29, 2021
Since the start of the pandemic, one common metric used by scientists is ‘viral load’ – a measurement of how many copies of the coronavirus are in a patient’s body.
When patients have a higher viral load – more copies of the virus – they’re more likely to give the virus to someone else.
As the coronavirus has mutated into new variants, its viral load has increased. Delta is now the most contagious variant for this reason.
In fact, according to Fauci, Delta is so contagious that even vaccinated people can spread it.
‘We have a Delta variant that has changed the entire landscape,’ Dr Fauci said on MSNBC on Wednesday night.
Nationwide, the variant is causing over 80 percent of cases – and in some regions, that number is upwards of 90 percent.
‘When you look at the level of virus in the nasopharynx of a vaccinated person who gets a breakthrough infection with Delta, it is exactly the same as the level of virus in an unvaccinated person who’s infected,’ Fauci said.
‘That triggered the change in the CDC guideline,’- referring to the agency’s recent backtrack on masking recommendations for vaccinated Americans.
In May, the CDC said anyone who had completed a full vaccination regimen – two shots of Pfizer or Moderna, or one shot of Johnson & Johnson – could go without masks everywhere.
But this week, the agency said that several groups of fully vaccinated Americans should go back to masking in public, indoor spaces.
This includes people living in areas with rapidly-rising Covid cases, teachers in K-12 schools, and parents with children too young to be vaccinated.
When announcing the change, CDC Director Dr Rochelle Walensky cited ‘new scientific data’ in line with Dr Fauci’s statement – vaccinated people can spread Delta.
The statement also aligns with a recent study from China suggesting that people infected with Delta have a viral load 1,000 times higher than those infected with older strains of the coronavirus.
But the CDC’s new data are not yet public, leading to concerns about the agency’s transparency.
People infected with the Delta variant had 1,000 times as many copies of the virus in their respiratory tracts as people infected with the original strain (above), a recent study found
A citation in the updated masking guidance simply reads, ‘CDC COVID-19 Response Team, unpublished data, 2021.’
These data come from investigations of recent Delta-caused outbreaks, in which researchers compared infections among vaccinated and unvaccinated people, according to the Washington Post.
The findings will be ‘published imminently’ per reporting from The Post.
But that’s not enough for some scientists – even those who have endorsed the CDC’s new guidance.
‘They’re making a claim that people with delta who are vaccinated and unvaccinated have similar levels of viral load, but nobody knows what that means,’ Dr Gregg Gonsalves, an associate professor at the Yale School of Public Health, told The Post.
‘It’s meaningless unless we see the data.’
Other experts aren’t convinced that a higher viral load actually leads to Delta’s transmission among vaccinated people.
‘I feel like nasal viral load is one part of a lot of other parts’ that determine how infectious a person is, biostatistician Natalie Dean told The Post.
Dean added that she thinks other important factors may be how much virus is present in a patient’s throat or lungs.
Experts like Dean want to see more data comparing case numbers between vaccinated and unvaccinated Americans.
In recent months, the vast majority of severe Covid cases – those leading to hospitalization and death – have occurred among the unvaccinated.
But the CDC is not tracking less-severe breakthrough infections. In May, the agency switched its strategy to only investigate and report those infections that cause hospitalization or death
Scientists have critiqued this move for leaving the U.S. without crucial data to monitor the cases caused by Delta and other variants.
Still, all Covid experts can agree on one thing: Delta is cause for major concern, and additional precautions are needed to curb its spread.
‘Delta is Alpha on steroids,’ James M. Musser, chair of the Department of Pathology and Genomic Medicine at Houston Methodist Hospital and Research Institute, told WaPo.