It's not always about investment. The question is rather, who benefits from advances in public health? The answer is insurers. The biggest insurer in the country by far is the federal government. They're going to want to learn and apply lessons for many years to come from this catastrophe. I suspect that NIH will ramp up public health funding, and other large insurers might spend some money on it too. I would go for the PhD of I were you. Don't stop at an MPH. You're smart enough, dedicated enough, so why not just go the whole way?