COVID Vaccine breakthrough cases are popping up in the news.
Is the Delta Variant responsible for breakthrough infections?
Do the Vaccines still work?
COVID cases, hospitalizations, and deaths are on the rise again. Right now, there are 162 million Americans who are fully vaccinated. According to the CDC, less than two percent of people hospitalized with COVID are vaccinated. And get this – 99.5% of people who die of COVID did not get the vaccine.
A COVID breakthrough infection is defined as someone who tests positive for COVID, with a PCR test, at least 14 days after being fully vaccinated. Several breakthrough infections have been reported at the White House, Congress, Olympics, Major League Baseball, and more. I’ve seen people with breakthrough infections in the ICU, but not nearly as much as COVID patients in the ICU who did not get the vaccine.
Covid Breakthrough Cases
Stanford is among nearly 600 universities and colleges nationwide that have required students and faculty to be vaccinated against COVID before coming back to campus this fall. Stanford 7 Vaccinated Students Get Symptomatic COVID in a week span.
Even before the delta variant showed up, we knew that the vaccines aren’t 100% effective. Based on the original studies, we knew that the mRNA vaccines with Pfizer and Moderna were about 95% effective at preventing severe COVID illness. This means that percentage is even smaller when you’re talking about preventing mild or asymptomatic infections. But the important thing you want to know is how effective the vaccine is at preventing severe COVID illness.
But that 95% effectiveness was based on the original strain of COVID. Now, the scarier and more contagious Delta variant makes just about all the COVID cases in the US.
According to this recent study, when people are infected with the Covid Delta variant, they have about 1000 times more viruses than previous versions of the covid virus. So all that viral load has the potential to overwhelm the immune system of vaccinated people.
Another study that was just published in the NEJM also showed that the delta variant is slightly more likely to cause breakthrough infections:
Researchers found that after two doses of the Pfizer vaccine, it gave 88% protection against symptomatic disease caused by the covid delta variant, compared to 93% against the alpha variant that was first discovered in the UK.
Both doses of the AstraZeneca vaccine offered 67% protection against symptomatic disease. According to the company, we’re still waiting on published numbers for the Moderna vaccine, but its vaccine remained effective against the different variants.
The Johnson & Johnson vaccine might be less effective against the Delta Covid and Lambda covid variants, but that study is yet to be published. It might be that those who received the J&J vaccine may need to get Pfizer or Moderna to protect against the new variants. So stay tuned on that.
We know that those vaccinated have milder Covid illness compared to unvaccinated if they become infected. This is based on another study published in the NEJM that looked at more than 3,900 essential workers. It shows that fully vaccinated people are more than 90% protected against infection. Even partially vaccinated people are 81% less likely to become infected than people who haven’t had been inoculated.
Vaccinated people appear to be less likely to spread the virus to others. After one or two doses of covid vaccine, those who got “breakthrough” infections had 40% less virus in their bodies and were 58% less likely to have a fever. They spent two fewer days in bed compared to unvaccinated Covid patients.
Then there is the question, if you’re asymptomatic and have been vaccinated, can you still spread the virus to others?
We know the vaccine reduces the likelihood of carrying the virus. And if you are carrying the covid virus, we know that there would otherwise be a reduced viral load. So overall, it’s less likely that you are transmitting the virus if you’re asymptomatic and you’ve been vaccinated. This is why the CDC says that fully vaccinated people still need to be tested if they have symptoms and shouldn’t be out in public for at least 10 days after a positive test. This is actually being studied right now in 12,000 college students who received the Moderna vaccine.
And what about those of you who are vaccinated and are concerned about getting a breakthrough infection?
If you were to get COVID, it’s way more likely to be a milder course of the disease if you are exposed to many people, especially if they’re not vaccinated; you can wear a mask. The kind of mask to wear is another topic, but even a regular face covering would still be better at decreasing transmission compared to no mask at all.
Doctor Mike Hansen, MD
Internal Medicine | Pulmonary Disease | Critical Care Medicine
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