An ingredient mix-up at a Baltimore manufacturing plant ruined 15 million doses of the Johnson & Johnson COVID-19 vaccine, The New York Times reported. That could delay future shipments of this vaccine in the United States.

There are not any problems with the doses of the Johnson & Johnson vaccine that have already been delivered — those were produced in the Netherlands, the Times reported. But the tens of millions of the shots set to ship in April were supposed to come from this Baltimore plant.

The manufacturing plant, run by Emergent BioSolutions, received $628 million from the Trump administration last year to expand its vaccine manufacturing capacity. The plant was still awaiting Food and Drug Administration authorization of its Johnson & Johnson vaccine production lines, and this enormous mistake — which Times sources attributed to human error — will likely delay that further. It’s not clear how this setback will affect the availability of this vaccine over the next few weeks.

Moderna and Pfizer / BioNTech are still on track to meet their vaccine commitments in the United States, which should give the country enough doses to meet the Biden administration’s target of having shots available for every adult by the end of May.

But limited availability of the Johnson & Johnson vaccine could still hurt US efforts to vaccinate enough people for herd immunity. People who are reluctant to get vaccinated against COVID-19 and say they’ll “wait and see” are more likely to agree to take the Johnson & Johnson vaccine than the Pfizer/BioNTech or Moderna shots. The Johnson & Johnson vaccine only takes one dose, and is made using a more familiar technique. Only having the Pfizer / BioNTech and Moderna shots on offer could make it harder to convince some people to get vaccinated.

Around 30 percent of the US population has received at least one dose of a COVID-19 vaccine so far.