User:Monil Mehta/sandbox

In late 2021, Cathy Angelini, the sales director at the St. Regis Residences Boston, an under-construction luxury condominium, was elated to have back-to-back showings after a long sales drought.

Things started well when a Pfizer employee agreed on the spot to purchase a 16th-floor condo with views of Boston Harbor for $4.85 million, she said. Two hours later, a Moderna executive honed in on the same unit. When she remarked on the coincidence, Ms. Angelini said, “He just looked at me, completely serious and said, ‘I want the same home, but I need to be one floor higher than Pfizer.’ ” He reserved the option to buy a 17th-floor unit for $4.95 million that day, she said.

Ms. Angelini’s buyer is just one in a flurry of Moderna employees who have descended on the Boston-area real-estate market since the company’s blockbuster Covid vaccine helped drive the company to its first profitable year in 2021, more than a decade after its founding in 2010.