Both these diseases- Measles and Rubella, have very similar symptoms, have similar complications and are often confused for one another. And both the diseases have a common MMR vaccine. So, are the culprit viruses also related, so that contracting one can give one at least partial immunity to the other as well?
The similarity in symptoms is striking. Both the diseases may start with cold and fever. Both give one rashes, that start from face, and spread to rest of the body. Both have similar complications associated with them like brain infection. In the end, both can cause miscarriage, preterm birth, or stillbirth, as well as a variety of birth defects in pregnant women.
I know from this source that lab tests exist which can tell whether a person has immunity to one of the MMR diseases (Measles, mumps and rubella) and not the other, implying that there is a possibility of immunity to one and not the other. But since the vaccines like MMR only ensure immunity for 99% people who get the shot, my question is- does there exist partial immunity (in some people and not others, or in less severe attack and not otherwise) to Rubella if one has contracted Measles before and vice versa?