Wanting to catch up, age 3.5 - any recommendations?

[WhiteHorse]

Basically, my son was up to date with the CDC schedule at his 6 month checkup. (I need to get his exact records to be sure which ones he got)  I know that some of the vax's are only relevant for younger children, and if I wait until he is 4, possibly some could be skipped (??). If you had to start catching up a 3-4 year old, which ones would you do?  Also, I am about to have a new baby, so exposure might be an issue for some of these. I do think summer would be a better time to start vaxes for my son as he normally spends the entire cold months sick. Thanks in advance!!

[Turquesa]

DTaP for sure because even though it's not the most effective vaccine, pertussis is one disease I'd like to avoid in my house.

ETA: We say it ad nauseum in this forum, but take a look at The Vaccine Book by Bob Sears. He gives a great synopsis of each vaccine, each diseases, each pro, each con...

[Lauren82]

The CDC actually has a downloadable tool that explains the catch up schedule based on your child's age and what vaccines they have already had.

http://www.cdc.gov/vaccines/recs/Scheduler/catchup.htm

As far as what vaccines to get, I think that's something that is going to be different for each parent. The book Turquesa recommended is great for learning about the different vaccines and diseases.