We’ve been watching the progress of the Johnson & Johnson vaccine since before it was approved by the FDA. The vaccine has some advantages in that it requires only one dose and can be kept in a normal freezer for transport. So when J & J was struggling to crank up production, it was big news when Merck stepped in to help. But even the best of plans can fail because of the most common of errors. In this case, a mistake by plant workers in Baltimore has spoiled 15 million doses of the vaccine.

Workers at a Baltimore plant manufacturing two coronavirus vaccines accidentally conflated the vaccines’ ingredients several weeks ago, ruining about 15 million doses of Johnson & Johnson’s vaccine and forcing regulators to delay authorization of the plant’s production lines.

The plant is run by Emergent BioSolutions, a manufacturing partner to both Johnson & Johnson and AstraZeneca. Federal officials attributed the mistake to human error.

The mixup has halted future shipments of Johnson & Johnson doses in the United States while the Food and Drug Administration investigates.

The story points out that all current doses of the vaccine are safe because they were produced in the Netherlands. But this plant in Baltimore was supposed to provide the next big push of doses and now it’s shut down until some quality control can be restored. As of yesterday, Emergent still hadn’t been given FDA approval to produce vaccines:

While Emergent has been shipping millions of doses to J&J’s U.S. fill-finish partner Catalent, which itself snared authorization last week, those shots can’t be used until Emergent earns its emergency nod. In the meantime, J&J has been flying in drug substance from the Netherlands, one source told Politico…

The issue stems from the fact that J&J didn’t include its manufacturing partners in its original emergency use application, Politico said. In recent weeks, Biden administration officials have raised flags about whether the company can meet its delivery goal.

But J&J says it’s on track to provide a promised 20 million doses by the end of the month and 100 million by June, a company spokesperson said via email.

So in this case it’s good news that doses from this facility hadn’t been approved by the FDA and therefore couldn’t be sent anywhere.

There are two obvious impacts from this. The first is that it’s going to probably put a dent in our vaccination numbers. As of today about 97.6 million have received at least one dose of a vaccine. The current 7-day average is 2.83 million doses delivered per day. But losing 15 million doses in the supply chain could create a setback, at least in terms of the continued improvement in the numbers. We’ll have to wait a week or two to see how the numbers change but we’ll still make Biden’s lowball timeline of 200 million doses in 100 days.

The other impact I can see coming from this is that a lot of anti-vaccination people will get worked up about the safety of the J&J vaccine. In this case the error was caught and nothing made it out of the plant, but it’ll still worry some people. For some, this might be the last straw that convinces them to stay away. That’s unfortunate because these vaccines are pretty amazing and work better than anyone could have expected.

I think the lesson here is one that Elon Musk has pointed out many times: Mass production is very hard:

“It’s relatively easy to make a prototype but extremely difficult to mass manufacture a vehicle reliably at scale. Even for rocket science, it’s probably a factor of 10 harder to design a manufacturing system for a rocket than to design the rocket. For cars it’s maybe 100 times harder to design the manufacturing system than the car itself.”

Vaccine production probably isn’t as complicated as building an electric car but the same general principle holds. We’ll get past this and this same factory will probably be a finely tuned machine in another three or four months. But obviously this is a situation where we needed those doses now and we just can’t afford many mistakes like this.