Cheryl Druehl, associate professor of operations management at George Mason University’s School of Business, details the many ways that distribution of the COVID-19 vaccine went wrong — and the lessons to be learned from it.

States haven’t received the promised number of vaccine doses in a timely fashion, but the reason isn’t entirely clear. It’s the result of multiple failures along the vaccine supply chain, including strict temperature-control requirements, equipment and driver shortages, and general snags in logistics.

The state of affairs shouldn’t come as a surprise, given the unprecedented scale of the pandemic. “It’s the largest mass vaccine that the U.S. and world have ever tried to do,” notes Druehl. Given that reality, it’s something of a miracle that manufacturers were able to develop a vaccine as quickly as they did.

Under the circumstances, “everyone is doing a pretty good job,” says Druehl. “As we move forward, things are starting to improve, and the vaccine numbers are going up.”

There was no real “playbook” for manufacturers and distributors to consult, even though they had encountered multiple outbreaks of viruses over the years. The focus became on getting the vaccine developed, with less attention at the outset on “nitty gritty supply-chain issues.” Now, Druehl says, there’s a heightened awareness of the importance of supply-chain management in times of crisis.

On the transportation side, parcel carriers such as FedEx and UPS have stepped up to handle final delivery of the vaccine to hospitals and other points of inoculation. In many cases, carriers have had to prioritize vaccine deliveries at the expense of regular e-commerce orders, but Druehl says consumers have generally been understanding of any delays in receiving orders of other types of products. “They’ve become more accustomed to not getting things on time,” she says.