Unpack CDC’s New Guidance
Congrats if you aren’t confused or agitated over CDC’s updated guidance last week! (I’ll have what you’re having!) But if you’re like many of my patients and medical colleagues, you’re scratching your head.
The short story: last week the CDC reversed its masking guidance for vaccinated people and is now recommending masks indoors for vaccinated people in areas where the risk of transmission is "substantial" or "high." (Note that masks have always been recommended for unvaccinated folks indoors.) The CDC also now recommends masking everyone in schools, regardless of vaccination status.
We already knew that the Delta variant is highly transmissible and is the dominant variant in the US — and as expected, we’re seeing breakthrough infections in fully vaccinated people. (For a case study of my vaccinated patient who got COVID-19, read my newsletter from last week.)
But on Tuesday when the CDC cited “new data” suggesting that vaccinated people are spreading the virus to other people even when they don’t exhibit symptoms, it sent many people into a tailspin.
My vaccinated patients were calling me: “Am I no longer safe with my unvaccinated grandchildren?” “Does the vaccine no longer work as expected?” “Are my unvaccinated kids now at higher risk?”
First, what was the source of the “new data” that prompted an about-face on masking? Well, it wasn’t terribly compelling. The data in a leaked CDC slide deck were quickly picked apart by scientists because the sole cited study had been rejected. Then the data on a cluster of Delta-related cases in Provincetown, Mass., over the Fourth of July weekend only accelerated the (inaccurate and poorly messaged) narrative that vaccinated people can be just as contagious to others as unvaccinated people. Media outlets ran with the story, the headlines only fanning the flames of anxiety.
So what’s the upshot here — does the sudden shift in masking guidance mean the vaccines are less effective? And how much should we worry? Let’s break it down.
What more do we know about Delta?
The Delta variant is a very “fit” version of the coronavirus. Delta replicates itself inside our noses fast — and faster than other variants — yielding peak numbers of viral particles on the very sensitive PCR tests. This means that some people may be more likely to develop symptoms than with previous variants, even when fully vaccinated. This, dear readers, has always been possible — and is why I wrote back in April: “Don’t be surprised when vaccinated people get COVID.”
The two burning questions are: how well do the vaccines stand up against Delta in terms of preventing #1) sickness and #2) infecting other people without having symptoms?
#1: How well do the vaccines protect us against COVID due to Delta?
The data are clear: Vaccinated people are extraordinarily well-protected from death and hospitalization due to COVID-19 and still are very unlikely to get COVID-19 in the first place — even from Delta. Vaccination has decreased the chance of death and hospitalizations from COVID-19 despite the increasing prevalence of Delta. The CDC reports that 97% of hospitalizations and 99.5% of deaths are among the unvaccinated.
The CDC’s own leaked data summarize the good news on Delta:
The vaccines offer 25-fold reduction against severe disease and death, and 8-fold reduction in symptomatic disease.
Fully vaccinated people can expect about 88% protection against symptoms and 90-95% protection against severe disease and hospitalization. This matches with new data from Public Health England showing 88% protection against Delta symptoms when fully vaccinated (compared to 93.7% against Alpha).
Breakthrough infections happen — more so with Delta — and we'll continue to see cases among the vaccinated until more people in the US are immune through natural infection or vaccination. Vaccination has de-fanged coronavirus and turned it into the common cold — though in some, the infection will be more severe than in others. This variation explains why some vaccinated people may choose to mask to protect themselves in high-risk situations.
The math on the severity of breakthrough infections for vaccinated people is reassuring:
The rate of breakthrough infection resulting in any symptoms is 0.02% (35,000 out of 163 million vaccinated).
The rate of breakthrough infection resulting in hospitalization is ten-fold lower at 0.003% (4,641 symptomatic hospitalizations out of 163 million vaccinated).
The rate of breakthrough infection resulting in death is another 10-fold lower at 0.0006% (954 out of 163 million vaccinated).]
Side note: Please remember the importance of context when reading eye-popping headlines about breakthrough infections like this one: Breakthrough COVID Cases: At Least 125,000 Fully Vaccinated People have Tested Positive. Two alternative headlines I’d propose that say the same thing: “Around 0.07% of vaccinated Americans have tested positive, and most of them have colds.” OR “The Vaccines Work. 99.93% of Fully Vaccinated Americans have NOT Tested Positive for COVID despite Delta!” Context matters!
The transmissibility of Delta may be higher, but the jury is still out on increased severity. (The 3 studies cited by CDC had significant weaknesses making it hard to tease out true severity.)
The vast majority of people who develop breakthrough infections experience mild or moderate symptoms like my patient did (these can include cough, headache, sore throat, muscle aches, sore throat or fever.)
#2: Do vaccinated people who don’t have symptoms really transmit the virus to other people as the CDC newly suggests? (This is the top question from my patients with unvaccinated kids.)
We’ve accumulated ample evidence over the last year that the COVID vaccines significantly drop — but don’t eliminate — the risk for transmitting the virus to other people. (Reducing risk to zero was never on the menu.)
But what about Delta? Are the vaccines less effective at preventing spread from non-sick vaccinated people with this more contagious variant? Despite the new evidence cited by the CDC and the Provincetown outbreak story, there is still no clear evidence that asymptomatic vaccinated people account for forward transmission of the virus to other people. Read this from one of the nation’s top vaccine scientists, Prof. Shane Crotty, or this from a top microbiologist if you need further reassurance on this.
In fact, what happened in the Provincetown outbreak provides an excellent case study on the power of the vaccines under heavy fire from Delta. (I’m quoted alongside Monica Gandhi, MD, MPH, in this Yahoo News! article which provides a good overview of the story.)
In short, it’s a story of about 60,000 tourists descending on a small resort town and packing themselves into bars and restaurants due to unseasonably cold, rainy weather. Most of them were vaccinated; many were not. The question isn’t why and how vaccinated people got COVID-19 (we know that vaccinated people can get COVID!); it’s how sick did they get (the answer: the vaccine protected the vast majority, and no one died) and did they sicken other people (the answer: we still don’t know, but it was probably the non-immune people who shed the most virus).
Is it possible that a vaccinated person in Provincetown could have felt completely well but still unwittingly spread the virus? Absolutely! This makes intuitive sense given how contagious the Delta variant is. Might we obtain more convincing data to show that non-sick vaccinated people are regularly sickening other people? We could! In the meantime, we can celebrate the fact that the vaccines performed well under pressure
In fact, data about Delta from Singapore, released on July 31st, explained that the viral load drops off more rapidly in vaccinated people 4 days after the infection. The facts remain that a vaccinated person is less likely to get infected and will be less likely to transmit following infection. The upshot? If you are vaccinated you are still well-protected, especially if you’re among other vaccinated people. Provincetown doesn’t change that.
Can vaccinated people who feel SICK due to a breakthrough infection transmit to other people?
Of course! This has always been true. Anyone who’s actually sick with COVID-19 — or any virus for that matter, regardless of vaccination status — can sicken other people. The solution to keeping other people safe? Stay home. Wash hands. Use good common sense.
So what’s the upshot for YOU?
Here’s what I am telling my vaccinated patients:
Delta is real and formidable. We cannot be shocked when vaccinated people get sick, especially if we live in an area of high transmission and low vaccine uptake.
Know your unique risks and risk tolerance. There is so much variability between our medical vulnerabilities, our behaviors, the nature of various exposures, and the environments we inhabit; it’s essential to root our behaviors in facts lest we get swept up in fear-based thinking and behaviors.
Mask indoors where it’s required, and consider masking indoors if:
You’re at high risk for complications of COVID-19 and would rather not take the risk of being in the tiny percentage of people who are vaccinated, get COVID, and land in the hospital and/or
You’re in an area where vaccination rates are low and COVID hospitalizations are high (i.e. where COVID is “in the air” more than other places. This map is a helpful resource.)
You’re exposed to someone with proven COVID, you live with a high-risk unvaccinated person, and you’re awaiting a COVID test (which should be done 3-5 days after an exposure).
Stay home if you’re sick.
Consider getting tested for COVID-19 if you’re sick and/or you live with a high-risk unvaccinated person. Do you need a COVID test every time you get the sniffles? No, but this is why you should have a doctor.
Kids continue to generally be at lower risk from COVID-19. For most healthy kids, COVID-19 is the common cold. Because Delta is more contagious, more kids will get infected and more kids will have colds. What’s crucial is that we protect our most vulnerable kids — those with underlying health conditions like diabetes, heart conditions, obesity, asthma — with every proven risk mitigation measure in place. I spoke about how to protect our highest-risk kids on Morning Joe on Friday. I’ll write more next week.
Last week the CDC stated that “the war has changed.” I’d revise this to say “the war is being won” through vaccination. The vaccines protect the vaccinee and the people around them. Are they perfect? No. But they’re pretty close, and they continue to pave the way toward our collective safety and sanity.
At the end of the day, we all want the same things: to protect ourselves, our families, and our communities — and to not live in fear. To me, the ticket to a good night’s sleep continues to be understanding the facts, listening to people I trust, putting medical data into context, and thinking critically for myself. And if this helps you, too, dear readers, I’ll sleep even better.
I will see you next week. Until then, be well.