The 'T' in 'DPT' vaccines isn't Typhus, it's Tetanus, aka lockjaw. Not contagious but the bacteria is widespread in soil hence need for earlier booster shots after trauma. Typhus is serious and has a vaccine, but hopefully few of us will need it.
On a more important point for this thread it should be mentioned that Dr. Sowell has a very personal, long standing, interest in autism, and its correct… and incorrect, diagnosis. His son started talking quite late. The family had many 'experts' tell them he had autism or mental retardation. However there are some children who are slow to start talking and have unusual early behavior, but have normal or high intelligence. They are difficult to sort out until they talk. IIRC his son is now fine and is an engineer. Hence his references to "late talking children" in the article. He was looking up everything he could find on autism long before most of us ever heard of it. He's also old enough to remember the diseases prior to their vaccines. I'm glad to see him write this now.
I have a particular interest in this topic, since I was also a late talker--I did not talk until the age of four. Apparently, before then, I would learn 3 or 4 words--and if I learned a new word, I forgot one I already knew. I have a very high IQ--above 150, but I don't know what it is. I surmise that I did not speak until I had figured out all the grammatical rules and was confident that I could speak correctly. I think this because even now, I do not do anything until I have it completely figured out so that I do not make a mistake.
My mother tells me that she took me to be evaluated at one point. The doctor told her that I was normal, she just needed to spend more time talking to me. Thank God the doctor had that insight, so I wasn't shoved into some special ed program.