I Have Antibodies, I Think
COVID Convos #37
Vaccine-induced Antibodies
I was given the Pfizer vaccine, and I really didn’t feel sick at all. Around the same time, my wife got dosed with Moderna and she also felt pretty decent. Why didn’t we feel ill? I wondered if we had missed out, or maybe something was wrong: did our immune systems not work? Were they bad batches of vaccine? Maybe I’m just really tough and don’t feel pain?…unlikely! Perhaps the fatigue, headaches, and muscle pain that we already have from being parents masked the vaccine side effects? (quite possible) This all prompted the question: How do we know if the vaccine even worked?!?
I was happy to just trust in the vaccine but one of us wanted to be more sure, so two antibody tests showed up in the mail. I don’t know where they were from or what they cost, but they appeared to be individual tests from a larger package, as there were no instructions or documentation. In other words, “these units not packaged for individual resale,” just like it says on each little bag of Pirate’s Booty that my kids pull out of the big sack. These tests may have come from a gray market.
No information, no instructions, and an unknown brand of test. Fortunately, I was able to find directions on Youtube. Sure, it seemed a little sketchy that the video had only been watched 17 times, but the instructions made sense even if the kit in the video didn’t exactly match the materials in my living room. It appears that our kit was a rebranded version of the Assure test, which has received FDA Emergency Use Authorization.
Is the test reliable? I read through the data submitted to the FDA, and most of the test validation was done with serum samples in the hospital setting. For results using whole blood from a fingerstick (like me, ouch!) 9 out of 9 patients who had had COVID 2+ weeks prior gave a correctly positive antibody result, while 9 of 9 negative controls were negative. 100% success, although the n of 9 on either side wasn’t hugely inspiring.
So how did we do?
Success! We have IgG, and the C is for control. At the time we took this test, we were both 2+ months out from vaccination. In this timeframe, IgM is expected to have faded, but long-lasting immunity with IgG is supposed to persist. The vaccines seem to have worked.
Caveats? I’m skeptical of antibody tests, for a few reasons:
#1: the true accuracy isn’t known, since the test was validated on so few patients.
#2: this test just gives a yes/no result; it doesn’t quantify if we have just a few antibodies, or an entire bloodstream full of them.
#3: having antibodies is nice, but it doesn’t guarantee immunity. The body’s immune response to COVID is complicated and multifaceted, and IgG is just one small part.
#4: For all I know, I could have put 2 drops of the included buffer solution on the test and it would have lit up a mark next to IgG. Unfortunately, the test kit did not include positive and negative samples with which to validate that the cartridge was actually testing for what we were looking for.
#5: technically, all this test tells me is that 2 drops of my blood light up the marker for IgG. It does NOT tell me that I’m necessarily immune to COVID.
Despite these caveats, do I feel good that this test says I have antibodies? Yes, yes I actually do.
