This is correct, IgG has a half life of about 21 days; generally this is good for 3 months of immunity

There's a period where immunity lapses, see: https://www.jwatch.org/pa201006020000002/2010/06/02/how-long...

I'm not actually sure why they vaccinate for MMR at one year as opposed to earlier like other vaccines. There must be a good reason.

The MMR vaccine is more effective after 12 months, i.e. there are fewer cases of the vaccine failing to confer immunity when first administered at 12 mos as opposed to earlier.

You can receive a first MMR dose earlier than 12 mos for certain grounds (e.g. international travel, military postings) but it is then recommended that the infant receive a second 'first dose' after 12 months.

IANAMD, but after looking at the vaccination plan for children last week, my guess would be that there's so many vaccines to be taken in the first two years of life that they have to sort it by priority and space out to balance risk of catching a disease with risk of overloading the body.

The evidence seems to indicate that vaccines don't cause some kind of "immune system overload". There are efforts underway to increase the number of vaccines given at a time.

https://www.who.int/vaccine_safety/initiative/detection/immu...

That's good to know. Doesn't stop midwifes from scaring us into considering combined vaccines that reduce the number of injections, solely by arguing that the more injections, the less safe it is for the baby.

Immume systems are fucking amazing[1]. There are millions of viruses and bacteria of all sorts everywhere in your house and outside that a child's immune system is constantly dealing to without you even being cognizant of it. And if it wasn't dealing with those successfully you'd very quickly know about it because your child has an immune disorder. The vaccines are absolutely infinitesimally small in terms of an immune reaction compared to this every day constant barrage.

[1] Except when they're broken, and then it sucks bad, and you find out how damn amazing they are and how much we take them for granted.

Does the human body process breastmilk differently as a child? Why can’t we immunize small populations of people or animals and use their milk to spread the antibodies to young and at risk populations?

We still don't know to synthesize breastmilk, even for babies (this is why breastfeeding is reccomended).

Also, it is a relativly recent development that adult humans can even digest milk. Lactose tolerence is the mutation, and a sizable portion of humans do not have it.

Sure but if it conveys immunity to measles in a measely area, I’m sure it would be pretty easy to convince some nursing mothers to nurse longer and sell the milk.