How does a person show agreement?
Use "so" and "too" to show agreement in positive statements.
Use "either" and "neither" to show agreement in negative statements.
All of the examples below are written correctly.
1a. I like soccer and so does he.
1b. I like soccer and he does, too.
1c. I don't like soccer and he doesn't, either.
1d. I don't like soccer and neither does he.
2a. She's a vegetarian and so is he.
2b. She's a vegetarian and he is, too.
2c. She's not a vegetarian and he isn't, either.
2d. She's not a vegetarian and neither is he.