That is what it felt like to memorize the catch-up immunization schedule (aka, a 15-month old comes into your office and mom says he hasn't been to a doctor since he was 6 months old - what immunizations are you going to give him today, and when should his next appointment be?).
Well if you are over 6 months old, then you can't get the rotavirus vaccine at all (you snooze, you lose). But you have to be at least 6 weeks old to start getting any doses of Rota, DTaP, Hib, PCV, IPV, or MCV. And you have to be at least 1 whole year before getting MMR, varicella, and hep A. But that's just the first dose!
Let's take Hib (Haemophilus influenza type B) as an example [the vaccine which has, by the way, drastically reduced the number of cases of meningitis, life-threatening epiglottitis (seriously, you don't even see that anymore), septic arthritis, osteomyelitis, and occult bacteremia in kids]. Ok, put your logic cap on, because this is where it gets tricky:
|this is my logic cap. find your own.|
If Billy received his first dose of Hib at younger than 12 months, then you have to wait at least 4 weeks before giving him the second dose. If the first dose was received between 12 and 14 months, then you have to wait at least 8 weeks to give the second dose! But if the first dose was given at older than 15 months, then he doesn't even need a second dose.
But don't worry, you're not even done with Hib yet. For the third dose, it's similar. A 4 week waiting period if current age (NOT previous dose) is less than 12 months, an 8 week waiting period if current age is greater than 12 months AND first dose was administered before 12 month and second dose before 15 months. And again, no third dose needed if second dose was given at older than 15 months.
And lastly, a fourth dose is only needed if all three previous doses were given before the age of 12 months.
That's just one of the vaccines (ok fine you got me, it's definitely one of the more complicated ones - some of them are only two doses with no caveats). And since we didn't know what aged child we would encounter on the exam, you had to* memorize the catch-up schedule for all possible ages.
I was half-expecting to see the question on the exam to say "So how many kids did Billy ride the school bus with on Wednesday?"
*were supposed to