Josiah Zayner’s plan was simple: replicate a Covid-19 vaccine that had worked in monkeys, test it on himself and then livestream the experiment online over a period of months. Now, that improbable bid is over.
Around the world, dozens of Covid-19 vaccines are in human clinical trials involving tens of thousands of people. While vaccines typically take years to develop, U.S. scientists are racing to produce one in months through Operation Warp Speed. But Zayner, a one-time NASA researcher who left the scientific establishment in favor of engaging in do-it-yourself experiments, bet that by working outside regulatory structures, he could test a vaccine even more quickly and certainly more cheaply by giving it to himself.
Instead, Zayner discovered, testing a vaccine is far more complicated than he had imagined. 
Even though his experiment yielded a promising result, Zayner found too many unanswered questions to say that it worked. For one, it wasn’t clear whether antibodies he found in his own body in extremely tiny measures before the experiment began made a difference. Zayner has long-believed that biohackers such as himself have the potential to make science move faster. In June, he told Bloomberg News that Covid-19 presented "the perfect opportunity" to show just what biohackers can do. 
Now, his message is decidedly different: “Human beings — their biology is so complex,” he said in a recent interview. “The results are going to be messy. The experiments are going to be messy. So you test 30,000 people so that the messiness kind of averages out.”
As the U.S. rushes to bring a vaccine to market far faster than has ever been done, Zayner said he has discovered why the long, slow process of clinical trials shouldn’t be rushed. A promising early stage result is just that: promising. It’s a message that’s resonating nationwide in the U.S. as the timeline for a development of a safe and effective vaccine has become a touchpoint in the presidential election, with President Donald Trump saying we could see an outcome before the Nov. 3 vote, Democrats worrying that he is putting a thumb on the scale,  and scientists saying it will probably arrive close to the end of the year, even in January.
Zayner is infamous for attention-grabbing experiments in which he uses himself as a guinea pig. He self- injected the gene-editing tool Crispr while giving a talk at a San Francisco biotech conference, and performed his own fecal matter transplant. Such stunts have made him an informal figurehead for a growing movement of do-it-yourself scientists emboldened by advancements in technology that have made such feats as engineering biology increasingly simple. Zayner believes such cutting-edge science should be accessible to anyone, and that democratizing science could help curb exorbitant drug prices and speed science along.
Initially, Zayner assumed that the experiment he named Project McAfee, after the antiviral software, would be relatively straightforward. The vaccine selected had  triggered protective immunity against the virus in rhesus macaque monkeys in a paper published in May. Zayner was able to order the same spike protein sequence from the DNA-synthesis company the researchers had used. The plan: He and two fellow biohackers — Daria Dantseva in Ukraine and David Ishee in Mississippi — would themselves test the concoction they ordered online. They would then livestream the entire process online over several months, with the first showing to occur in June.
But early on in the experiment, complications arose. Before starting, Zayner took a test at Lab Corp Inc. that told him he didn’t already have antibodies to the virus. But when he performed a similar test on himself shortly afterward, he found that he did have some antibodies, just not enough to produce a positive result on Lab Corp’s test. While those antibodies didn’t appear to be the neutralizing type, he wondered whether the result came because the vaccine was picking up signals from antibodies to a different virus — or how this faint antibody signal might affect things. 
“I’m very suspicious of my own data,” he said.
He’s not alone. Hank Greely, a bioethicist at Stanford University, said Zayner’s experiment pointed out an underappreciated reality of vaccine development. “Actually making the vaccine isn’t that hard,” he said. “It’s testing it and knowing that it’s safe — and knowing that it’s effective.”
Greely said that while Zayner’s DIY experiment probably presented more risks than potential benefits, there  is value in demonstrating to people that vaccine development isn’t “magic.”
For his part, Zayner said his turn at vaccine testing has tempered his appetite for DIY human experimentation. He still believes such experiments have a role to play, especially for those with fatal illnesses that lack approved treatments. But for now, he's taking a break from experimenting on himself.  His next project will focus on showing people how to grow chicken cells to make their own fake meat. 
With vaccines, Zayner 

concluded, “Large scale clinical trials are probably required, because it is so messy.”

Bloomberg