I only know what I read. Christakis is indeed in the sociology department, but he's also MD, MPH from Harvard, so I don't think I'd label him as just a sociologist. So here's a quick google. Joel Baines is a virologist at LSU. He states that we don't know how long immunity will last. I'm not a trained expert in the field, so I will defer to expertise. Can you explain why Joel Baines is incorrect?

The other factor in avoiding reinfection is how good the antibodies are that people are making against the coronavirus. Humans almost always make antibodies when exposed to a virus. But not every antibody is powerful enough to block a virus from infecting cells again — and scientists have yet to discover whether the coronavirus antibodies are high-quality ones.

"Do they neutralize the virus, which means binds to a very specific place on the virus that will prevent the virus from attaching to the cell it would normally infect?" Lund said.

Even if the antibodies are capable of this, the immunity they provide could wane over time.

"Because this is so new, it's hard to predict what's going to happen," said Joel Baines, a virologist at Louisiana State University. "There's going to be a period of immunity, and it could be as little as eight months to a year, and as long as several years."

https://www.nbcnews.com/health/health-news/can-you-catch-coronavirus-twice-you-ll-probably-be-immune-n1171976