According to a US government document, the Delta variant of the coronavirus is as infectious as chickenpox, produces more severe illness than previous strains, and breakthrough cases in vaccinated people may be as transmissible as unprotected cases.
The Centers for Disease Control and Prevention (CDC) emphasizes in an internal PowerPoint presentation that “the war has changed” as a consequence of Delta.
The Washington Post broke the news first, and AFP confirmed it.
Data from the presentation this week was used by CDC director Rochelle Walenksy to support a return to masks for vaccinated individuals in high-risk regions.
The discovery that breakthrough infections in vaccinated individuals are extremely infectious, based on prior research and a recent study of an outbreak in Provincetown, Massachusetts, is one of the most important conclusions.
The cycle threshold (Ct) value is used by experts to determine how much virus an infected individual has, with lower values suggesting a greater viral load.
In Provincetown, there was “no difference in mean Ct values in vaccinated and unvaccinated cases,” the slides said.
The CDC released a preliminary assessment, estimating that approximately three-quarters of individuals were vaccinated.
According to local sources, the outbreak was linked to July 4th celebrations, with the latest number of persons affected rising to 900.
However, unlike past major outbreaks, hospitalizations are minimal, with just seven reported so far and no fatalities, according to the news website MassLive.
Celine Gounder, an infectious diseases physician, and professor at New York University told AFP,
“This is a key point which is part of the reason the CDC changed its guidance,”
“It’s not really so much for your own protection: as a vaccinated person if you have one of these breakthrough infections, you may have mild symptoms, you may have no symptoms, but based on what we’re seeing here you could be contagious to other people.”
As a result, the CDC has updated its advice to advise that even if they don’t have symptoms, vaccinated individuals should be tested if they’ve been exposed to the virus.
Jennifer Nuzzo, an epidemiologist at Johns Hopkins University, pointed out that the Provincetown pandemic happened in an environment where community transmission was minimal, thus the CDC’s new masking guideline would not have applied.
“Moreover, public reporting around that outbreak investigation suggests (s) that exposures were likely at places like bars and house parties, where mask-wearing would be unlikely,” she told AFP.
Breakthrough infections, according to the CDC slide set, are not as uncommon as previously believed, accounting for “35,000 symptomatic infections per week among 162 million vaccinated Americans.”
While the original SARS-CoV-2 was as infectious as the common cold, each person with Delta infects on average eight others, making it as contagious as chickenpox but less so than measles, according to research from other nations.
According to reports from Canada and Scotland, it may be more severe, with a greater likelihood of hospitalization. It also increased the likelihood of ICU hospitalization and mortality in Singapore.
Vaccine effectiveness estimates vary by country, but the CDC estimates that the risk of serious illness or death in the vaccinated is decreased 10-fold or more, while the chance of infection is reduced three-fold or more.
That translates to at least 90% effectiveness against serious illness and death, as well as at least 67% effectiveness against infection.
While greater masks may be able to limit the spread, experts believe vaccinations are still the best way to combat the health problem.
The White House said Friday that half a million individuals had gotten their first vaccination injection, the greatest number since July 1.
A little under half of the population is now completely vaccinated, with just over 60% of adults being fully vaccinated.