The truck targeted football fans in the US city of Charlotte with a direct message: "Don't get vaccinated".
Beneath the stark white text on a digital billboard was the name and website of Wilmore Funeral Home.
The shocking targeted ad turned heads, as was intended, but all was not as it seemed.
The funeral home featured on the truck did not exist - and anyone visiting the website saw this message instead: "Get vaccinated now. If not, see you soon."
They were then directed to a service offering vaccines.
The whole enterprise was the brainchild of an advertising firm, BooneOakley, who were looking to improve low vaccination rates.
Charlotte is in North Carolina, a state where less than half the population is fully vaccinated.
"I just feel like conventional advertising is not working. Like, just regular messages that say 'Get the Shot' or 'Go Get Vaccinated' ... they just kind of blend in with everything else," agency director David Oakley told CNN.
"We wanted to do something that saw it from a different perspective and kind of shocks people into thinking, 'Holy moly, man.'
"I believe even if just one person gets vaccinated because of that billboard, I give it a grand success. Just one person, it will be worth it to me," Oakley added.
Oakley admitted that StarMed, the vaccination service they directed people to, was initially nervous about the idea but soon came round.
The clever campaign received a good reception online, with one Twitter user calling it "God-tier marketing".