Construction began Sunday on a massive drive-through COVID-19 vaccination center in the parking lot of a former Babies R Us outside the King of Prussia Mall.

Two arches, 140 feet by 30 feet, sprouted to serve as a 10-lane carport. Workers installed several retrofitted shipping containers to serve as emergency units in which medical professionals could store the highly perishable vaccines. Additional carports would service four more lanes of traffic for testing and vaccinations.

But the future of the project, under the auspices of COVID-19 testing firm 15toKnow, is far from a done deal. Its future as a vaccination center is uncertain. It’s being built on spec, a sort of Field of Dreams scenario.

Mike Dershowitz, CEO of locally based 15toKnow, said there’s no guarantee the Pennsylvania Department of Health will allocate vaccinations to his for-profit enterprise.

“We put up this site to better understand for ourselves how we would operate a large-scale vaccination site. At full capacity, assuming we have the doses, we could handle 3,000 a day,” Dershowitz said. “We’re trying to show that we’re ready. We’ve gotten good at car-based testing.”

The Montgomery County Commissioners were not aware of the proposed vaccination site, a spokesperson said.

According to an Inquirer analysis of state Health Department data, the four suburban Philadelphia counties have been shortchanged in the distribution of COVID-19 vaccines, receiving far fewer doses relative to population than smaller counties in the state. One of the three most populous counties in Pennsylvania with 830,915 residents, Montgomery County ranked 20th in dose rates — 17,667 per 100,000 residents, the analysis showed. Chester County ranked 29th with 14,748 doses per 100,000 residents; Bucks 34th with 13,103; and Delaware 53rd with 9,113.

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Montgomery County has two vaccination sites: Montgomery County Community College in Blue Bell, which can dispense 1,000 doses a day, and the Norristown Area High School gymnasium, which also has injected about 1,000 vaccines a day. A third location is under consideration but will not be in a King of Prussia parking lot, the county spokesperson said.

A spokesperson for the state Health Department could not be reached for comment.

Whether the King of Prussia site becomes a vaccination center is not Ricky Rose’s responsibility. That it gets built is.

Rose is the CEO of Mountain Productions, the upstate Pennsylvania-based company that builds complex staging structures for major music festivals. At this time last year, he was planning the concert setups for Firefly, the annual three-day music and camping festival celebrated annually in Dover, Del.

The pandemic canceled Firefly and shut down all of Rose’s other festival clients. COVID-19 leveled his concert business last year and put his 150 employees out of work.

Constructing testing and vaccination centers has become the bread and butter for Mountain Productions, headquartered in Wilkes-Barre.

Reinventing the company, founded in 1979, to help crush the disease has allowed Rose to bring back 50 workers. Mountain Productions has built about a dozen COVID-19 testing centers in nearly as many states.

Rose, 31, plans to complete the King of Prussia project — from fabrication to installation —- in less than a week.

He called the pandemic “the biggest event of our era.”

“It’s the crisis of our time,” Rose said. “By innovating and adapting, we’re doing our part to battle it. Live events right now are nonexistent. When the pandemic is beaten back, we hope we can rebuild the industry and get back to doing what our business was built for.”