Haha...I just figured out why they aren't real keen on using seroconversion tests for pertussis vaxes:
They don't know what's going on at all. They don't know which components (the different toxoids, bacterial antigens, etc.) give protection, if some are worthless, etc. They just have no idea, so they put a little bit of everything in there and hope for the best.
So, we're left with placebo controlled trials for efficacy. Here's the best I could find:http://cat.inist.fr/?aModele=afficheN&cpsidt=3699171
|The vaccine efficacy after two doses was 55 percent (95 percent confidence interval, 12 to 78 percent), on the basis of 14 cases in the DTP-toxoids group and 31 in the DT-toxoids group that met the definition of the World Health Organization. Conclusions. A pharmacologically inert, acellular pertussis-toxoid vaccine that is easily standardized is safe and confers substantial protection against pertussis.
The American acellular vaccines are based on the Swedish ones, and there haven't been any placebo controlled trials on ours, but the Swedish trial are used as the expectation basis.
So, 2 doses cuts the risk of pertussis in half. My wild guess is that one dose does about the same thing, and 5 doses probably doesn't bring it up much from there, either. But it looks like nobody's studied what happens with one dose. So who knows?
I have read that 5 doses can bring the efficacy up to as high as 80%.
So maybe the protection goes up 10% with each shot after the second? Or maybe one dose would only provide 40% protection?
It sucks that this hasn't really been figured out in some logical way.