The plural of “anecdote” is not “data” but the episode described here is noteworthy for more than one reason, starting with the fact that the author, Allan Massie, is an epidemiologist at Johns Hopkins. He studies infection for a living, so he knows what it means when a group of supposedly immune people discover that they’re not as immune as they thought.

The now-famous Provincetown study on which the CDC’s new mask guidance is based speculated that the huge July 4 outbreak there involved transmission between vaccinated people — but couldn’t prove it. It’s possible that the hundreds of vaxxed locals who were infected with the virus were exposed by unvaccinated people in their midst, as unvaccinated people might have higher viral loads than the vaccinated do. (The jury’s out for now although we know what the P-town study says.) But unless Massie left out an important detail about an unvaccinated person being around him and his friends at their party, one is forced to conclude that this was indeed a case of vaccinated people transmitting the virus to each other. Enough to make each other sick too, although not to the point of needing hospital care.

In that sense, what he describes shows that the vaccines are still doing their job. No one at the party has gotten severely ill (yet?), it seems. But vax-to-vax transmission is something that didn’t happen with pre-Delta strains of the virus, which is why the CDC told immunized people to remove their masks and get back to normal in May. If in fact Massie’s group involved the vaccinated infecting the vaccinated, it strengthens the case for the new guidance asking the vaxxed to mask up again. And it undercuts one of the core criticisms of the Provincetown study, which was that huge numbers of people packed into poorly ventilated bars on a holiday weekend isn’t representative at all of how most vaccinated people interact in daily life. The crowded P-town bar scene made for ideal conditions for the virus to spread. A small dinner party among vaccinated friends would be different.

But it wasn’t different, according Massie. And the “mild” case he contracted was mild only in the technical sense.

Five days earlier, I had gone to a house party in Montgomery County. There were 15 adults there, all of us fully vaccinated. The next day, our host started to feel sick. The day after that, she tested positive for COVID-19. She let all of us know right away. I wasn’t too worried. It was bad luck for my friend, but surely she wasn’t that contagious. Surely all of us were immune. I’d been sitting across the room from her. I figured I’d stay home and isolate from my family for a few days, and that would be that. And even that seemed like overkill…

Then, I started to hear that a few other people who had been at the party were getting sick. Then a few more. At this point, 11 of the 15 have tested positive for COVID.

Fortunately, none of us seems to be seriously ill. When fully vaccinated people experience so-called “breakthrough” infection, they tend not to progress to serious disease requiring hospitalization, and I expect that will be the case for us. But I can tell you that even a “mild” case of COVID-19 is pretty miserable. I’ve had fever, chills and muscle aches, and I’ve been weak enough that I can barely get out of bed. I don’t wish this on anybody.

If this wasn’t a case of the vaccinated infecting the vaccinated, what was it? The only possibility I can come up with (unless Massie omitted something) was that one or more of the attendees was lying about their vaccination status in order to attend the party, which would be reckless and selfish in potentially placing friends at risk of infection. Everyone there seemingly still benefited from getting their shots since no one ended up in the ER, but clearly we’re past the brief stage now where the vaccinated could get fully back to normal with near-zero risk of a symptomatic breakthrough infection. In fact, Massie’s urging the CDC to update its guidance and encourage vaccinated people to mask up and isolate once they know they’ve been exposed to someone who’s infected. The current guidance is still following the pre-Delta regime in which the vaxxed didn’t need to change their behavior after exposure.

The Times had a story this week about doctors surmising from their latest wave of patients that Delta is hitting people harder, not just faster. This is also an “anecdote, not data” problem since it’s based mostly on observations by physicians in hard-hit states like Louisiana, where the virus is rampaging. It may be that they’re seeing more severe cases now only because the total population of infected people is much larger with Delta than it was with earlier strains. Whatever the explanation, some young adults with no underlying health problems are being wrecked by the virus, leading doctors to describe it as a “younger, sicker, quicker” phenomenon. One went so far as to call Delta “a new COVID” because of how it affects the young. There is some actual data out there that suggests Delta leads to more severe illness:

Patients infected with the variant [in Scotland] were at nearly twice the risk of being hospitalized, compared with those infected with the earlier Alpha variant. The patients also were younger, presumably because they were last in line to be vaccinated, the authors said.

In a preliminary study posted online and not yet peer-reviewed, Canadian researchers found the risk of being admitted to intensive care was nearly four times as high in patients with the Delta variant, compared with patients infected with other variants. Patients with the Delta variant were at twice the risk of hospitalization or death.

Research in Singapore, which is to be published in The Lancet, concluded that patients with the Delta variant faced higher odds of requiring oxygen, needing intensive care, or dying. And a study in India, which was also posted online and not yet peer-reviewed, found that in the second wave of infection, when the Delta variant was dominant, patients faced a greater risk of dying, especially those under the age of 45.

That might help explain why Massie is laid up even though he’s not “severely” ill. Get smacked by Delta when you’re unvaccinated and you might land in the ICU; get smacked by it when you are vaccinated and you might land in your own bed. That’s a vastly better outcome, but immunization is no longer an impregnable shield against symptoms. At least, not until boosters are approved or Pfizer and Moderna tweak their formulas to target Delta specifically.

I’ll leave you with this from CNN, another case of Rochelle Walensky sitting on data instead of releasing it to the public. Make of it what you will. I’m guessing per Massie’s story that the ratio of unvaxxed to vaxxed in the hospital has gone down rather than up after Delta, although that’s partly because it couldn’t get much higher than it already was.

Multiple officials have cited figures saying 99 percent of deaths are among the unvaccinated and 95% of hospitalizations are unvaccinated. But CDC Director Walensky says those numbers are based on data from Jan—June & “didn’t reflect the data we have now from the Delta variant."

— Kaitlan Collins (@kaitlancollins) August 5, 2021