At the dawn of COVID-19 in 2020, supermarket shelves were swept clean of paper towels, bleach, and hand sanitizer. In the throes of the pandemic in 2021, a container ship that ran aground in the Suez Canal and blocked shipping for weeks was blamed for a shortage of everything from Peloton bikes to electronics to clothing.

Now, in the most serious consumer shortage yet, parents are scrambling to find formula to feed their babies.

The causes differ. Earlier shortages were sparked by panic buying and shipping disruptions. The latest case, however, has roots that are two-fold: the temporary loss of a major manufacturer and a reduction in imports.

The most immediate cause was the shutdown of Abbott Laboratories' Michigan plant in February after its formula was suspected to have sickened four babies, killing two. But it was the signing of a new 2020 North American Free Trade Agreement made in the waning days of the Trump administration that set the stage for the shortage.

Under the agreement, Canada agreed to stop underselling so-called Class 6 and 7 milk products, including dehydrated milk and infant formula. In theory, this would discourage Canadian exports to the U.S. and make U.S. exports more competitive. In practice, it made us more vulnerable to a disruption in domestic formula production. Complicating matters is the Food and Drug Administration's stringent rules for importing baby food, which has eliminated most European producers from the market.

This policy is worrying mothers that they will run out of formula and that their babies will receive insufficient feedings. It also affects caregivers who can't nurse infants, including foster mothers and other legal guardians.

The blithe retort that women should just breastfeed is ignorant. For many working women, breastfeeding is challenging, and for some, it's physically impossible.

Solutions are at hand. The FDA is expediting approvals of new imports. Abbott Laboratories has reached a preliminary agreement with the FDA on cleaning its Michigan facility, even though the CDC found no link between the company's product and infantile illness.

In the U.S., we have grown accustomed to full supermarket shelves. If the epidemic has exposed any weakness, it is in food production and delivery solutions.