How Contagious Is Delta Really?
Delta is more contagious than the original COVID-19 virus, and even more contagious than other variants of concern. This is why the CDC recently recommended disguising in some situations, even if you are vaccinated – something many public health experts have called for since Delta began to spread.
So how contagious is it? A recently leaked CDC document contains some new data to put it in perspective.
CDC slides show a rough estimate of Delta’s infectiousness and mortality rates based on a New York Times graph obtained earlier during the pandemic.
Delta may be slightly more deadly than the original COVID (SARS-CoV-2 is the official name for the COVID virus), but crucially, it is much more contagious. The common cold and various flu viruses are about as contagious as the original COVID, but Delta is far more contagious. Not nearly as strong as measles, the classic super-chairman, but roughly in the same range as chickenpox.
If you’re old enough to remember childhood chickenpox outbreaks, it sucks . I contracted chickenpox just a few years before the chickenpox vaccine was available, and as soon as one child in our area got it, our parents realized that most likely everyone would get sick sooner or later.
Do vaccinated people spread Delta?
If you’ve heard that vaccinated people shed as much virus as unvaccinated people, this is true, but only for people who actually get sick . Vaccinated people are unlikely to become infected with Delta or any other variant of COVID. On the rare occasion that they do this, it is when they have the same viral load as unvaccinated and infected people.
People who are vaccinated and have not contracted a Delta infection do not spread the virus or excrete viral particles, proteins, or anything else. The problem is not with the vaccine, but that the vaccine is not perfect.
“Delta breakthroughs can be transmitted in the same way as unvaccinated individuals,” the CDC said in a presentation. Prior to Delta, it was thought that breakout cases were arguably less contagious than cases in unvaccinated people with COVID.
To be completely clear about what the vaccine does for us, the CDC’s evidence is that vaccines work well. Currently, unvaccinated people have an eight times higher incidence of COVID than vaccinated people and have a 25 times higher risk of dying from COVID.
The CDC presentation states that “given the higher transmissibility and current vaccination coverage, universal masking is essential to reduce transmission of the Delta variant.” The CDC opted for a less drastic message in its ad the other day, recommending masks based on your personal situation and the level of transmission in your county. But it is also important to note that the more people are vaccinated, the spread of Delta will slow down and masks may not be needed when the number of cases is low enough.