Can kids younger than 1 year old get rubella? If yes, do they develope an imun response, protective anticorps?

Yes. It's possible to get rubella (german measles) at any age if not immunized. If a woman was immunized against rubella before pregnancy, some of her antibodies cross the placenta and protect the baby until about 1 year old. If the mom isn't immune, the baby is at risk. If a baby gets rubella under 1 year old, antibody levels must be done afterward, as many still will need the shot for protection.
Yes. Rubella is a devistating disease that has its worst effects on an infected fetus & lessens in its damage to infants, todlers & children as they age.Maternal antibody protects well for about 6mo & interferes with the vaccine until 1yr.We often vaccinate >6m if travel in a risk area is planned & repeat again at a year and 4-5yr. Ob's vaccinate after a delivery if mom not immune to protect next preg.