How Likely Are Vaccinated People To Get Meaningfully Sick From Delta?

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Dylan Housman Deputy News Editor
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The reality that breakthrough cases exist and being vaccinated doesn’t guarantee protection from COVID-19 has raised a new question in the minds of many Americans: just how likely is it that someone will get seriously ill from the delta variant of COVID-19 if they are vaccinated?

Some clinical data suggests that vaccine efficacy may be slightly lower against the delta variant than previous iterations of the virus, but the overall numbers are still promising. A July study by Public Health England found that the Pfizer vaccine is still 88% effective at preventing symptomatic disease from the delta variant, only about 6% lower than against the alpha variant. A Canadian study found the Moderna jab to be 72% effective against Delta after just one dose, but more data is needed to determine how much more protection the second dose provides. The Moderna shots have shown to be around 93% effective after six months without accounting for the Delta variant.

The Centers for Disease Control and Prevention (CDC) reported 6,915 hospitalizations related to COVID-19 in vaccinated people as of Aug. 2, but the answer to how risky COVID-19 is for the vaccinated isn’t as simple as a single stat. Anecdotal accounts and a deep dive into the data indicates that a wide variety of experiences are possible when vaccinated and infected.

The CDC doesn’t track or publicly release nationwide breakthrough case data. For that reason, it’s impossible to know exactly how frequent breakthrough cases are, how many of them are asymptomatic or how many result in just mild symptoms. It’s also less likely that asymptomatic or mildly sick individuals will think to get tested for COVID-19, especially if they are vaccinated.

“I took some Tylenol and went about my week … COVID never crossed my mind,” teacher Melissa Morelli said in a recent AARP story about breakthrough cases. “In hindsight, I wish I had thought about it more and went to get tested after I had some cold symptoms.”

Morelli didn’t get tested for COVID-19 until she ended up in the emergency room for a different issue, a heat-induced faint. Her symptoms related to coronavirus were limited to a stuffy nose, a mild headache and a slight cough. (RELATED: ANALYSIS: Pfizer Is Lobbying The Government For Third Vaccine Doses, And It Could Make Them Billions)

While the CDC isn’t providing national data, there is some state data that indicates Morelli’s experience is far more common than ending up in the hospital or dying once vaccinated. The CDC has reported that about 93% of recent COVID-19 that have been sequenced are the delta variant, meaning that the overwhelming majority of current data reflects the impact of that strain specifically on patients. ‘

According to the Kaiser Family Foundation (KFF), only half of states provide official data on breakthrough cases, although some information can be gleaned from others thanks to outside sources. Some of those states provide fairly large samples to extrapolate from.

In California, just under 21 million people are fully vaccinated. Just over 21,000 of them have been diagnosed with COVID, for an infection rate of just 0.1%. The rate is likely higher due to asymptomatic cases, but it’s unknown by how much. Of those infected, only 934 were hospitalized, and 93 died.

KFF notes that not every state distinguishes between those who are in the hospital with COVID, and those who are in the hospital because of COVID. For instance, in Washington, D.C., as of July 11, only 50% of hospitalized breakthrough cases were known to be directly caused by COVID.

Even if every hospitalization and death reported in California were confirmed to be COVID-19-induced, that’s a hospitalization rate of about 4.4% and a death rate of about o.4% for those who are diagnosed. When only 0.1% of those who are vaccinated have been diagnosed with the virus, those are astronomically low odds of serious illness for the vaccinated.

Not every case that fails to reach the hospital is a walk in the park, though. Conservative journalist Brandon Darby recently outlined his battle with COVID-19 on Twitter despite being fully vaccinated. (RELATED: This Is How Much The NIH Actually Cares About COVID-19)

“Recently cared for someone while they were sick with COVID and now I have a breakthrough case. I’m on day 6 of being sick. I’m ok. Doesn’t feel good though,” Darby wrote Sunday. “I woke up on day 3 and felt like death. I had a very high fever and it felt like my joints were on fire and being hit with a hammer at the same time. My whole body hurt.”

“Like day 3, day 4 was also miserable and the headache became more pronounced. Almost unbearable, but it started to subside during the day,” he continued. Darby said he experienced “only two bad days” but that otherwise the symptoms were like that of a seasonal cold or allergies. Still, his tale is a firsthand account of the kinds of cases that the CDC currently doesn’t count: cases where someone does get quite sick, but not enough to end up in a hospital.

Still, the overall data says that the answer to the original question, how likely is someone to get meaningfully sick from the Delta variant if they are vaccinated, is “highly unlikely.” The second largest dataset with diagnosed cases tracked by the KFF comes from Michigan. Among its population of 4.8 million vaccinated, 0.16% have been diagnosed with the virus. 0.01% have been hospitalized. 217 have died.

From what the CDC does report, only 0.003% of vaccinated Americans have ended up in the hospital. 0.0007% have died. Those are good odds.