US CDC: With Delta, Vaccinated People May Be As Contagious As Unvaccinated

An internal CDC document says more breakthrough infections and community spread are expected with the Delta variant despite Covid-19 vaccination, although vaccines prevent more than 90% of severe disease.

KUALA LUMPUR, July 30 — Vaccinated people infected with the Delta variant of Covid-19 may transmit the virus as much as unvaccinated individuals, according to an internal document by the United States’ Centers for Disease Control and Prevention (CDC).

The Washington Post reported yesterday a slide from the internal CDC presentation that referenced an outbreak in Barnstable County, Massachusetts, where vaccinated and unvaccinated people shed almost identical amounts of virus. 

“I think this is very important in changing things,” Walter A. Orenstein, associate director of the Emory Vaccine Center, told The Washington Post.

An anonymous person working in partnership with the CDC on investigations of Delta told The Washington Post that the data was from a July 4 outbreak in Provincetown, where genetic analysis revealed that inoculated people were infecting other vaccinated people. 

The US CDC also said in its internal document that Delta is as transmissible as chickenpox, and that the variant may cause more severe disease than Alpha or original strains. The federal American agency cited data from Canada, Singapore, and Scotland that showed higher probabilities of hospitalisation with Delta. 

In Singapore data cited by the CDC, infection with Delta was linked to higher risk of oxygen requirement, intensive care unit (ICU) admission, or death.

The CDC’s internal document noted that vaccines prevent more than 90 per cent of severe disease, but may be less effective at preventing infection or transmission, thus more breakthrough infections and higher community spread may occur despite vaccination.

The document said the CDC now needs to acknowledge that “the war has changed” and to improve public understanding of breakthrough infections. The CDC document however stressed that vaccines reduce the risk of severe disease or death 10-fold or higher, besides a three-fold reduction in risk of infection.

Columbia University epidemiologist Jeffrey Shaman, who reviewed the CDC slides, told The Washington Post that the main issue was that vaccinated people are “probably involved to a substantial extent in the transmission of Delta.”

The alarming findings led the CDC to draft a new guideline for fully vaccinated people in the US, retracting an initial May guideline that permitted fully vaccinated people to not wear masks.

In order to reduce the risk of coronavirus transmission by fully vaccinated people, the CDC now recommends wearing a face mask in potential public indoor settings that can spark substantial or high transmission. 

Fully vaccinated people were also asked to wear masks in casual indoor settings, when there are any immunocompromised or at-risk or unvaccinated household members.

The internal CDC document also stated that regardless of vaccination status, elderly people are being exposed to a higher risk of hospitalisation and mortality compared to younger people.

These findings have further complicated the role of CDC in gaining the trust of Americans on the effectiveness of Covid-19 vaccines and pushed the agency to revamp its communication method to improve people’s understanding of the new Covid-19 battle, The Washington Post reported.

“Although it’s rare, we believe that at an individual level, vaccinated people may spread the virus, which is why we updated our recommendation,” an unknown US federal health official was quoted as saying. 

“Waiting even days to publish the data could result in needless suffering and as public health professionals we cannot accept that.”

According to The Washington Post, there are 35,000 symptomatic infections being recorded in a week among 162 million vaccinated US population.

The CDC now needs to convince Americans on Covid-19 vaccine efficacy, while acknowledging fresh infections among fully vaccinated people without undermining the public’s trust towards vaccines.

“We’ve done a great job of telling the public these are miracle vaccines,” Matthew Seeger, a risk communication expert at Wayne State University in Detroit was quoted as saying.

“We have probably fallen a little into the trap of over-reassurance, which is one of the challenges of any crisis communication circumstance.”

The Washington Post reported that according to the CDC document, Covid-19 vaccines are not as effective among people with compromised immunity and nursing home residents, raising the possible need to give booster shots to some high-risk people. 

The US paper also cited Singapore and mentioned that 75 per cent of new Covid-19 cases occurred among those who are partially or fully vaccinated in the country. 

This has proved that achieving herd immunity for Covid-19 is extremely challenging with the emergence of the contagious Delta variant. 

“We really need to shift toward a goal of preventing serious disease and disability and medical consequences, and not worry about every virus detected in somebody’s nose,” Kathleen Neuzil, a vaccine expert at the University of Maryland School of Medicine was quoted as saying.

“It’s hard to do, but I think we have to become comfortable with coronavirus not going away.”

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