" A sizable amount is attributable to the environment, and this influence is poorly understood. A new area of genomic research called epigenetics is starting to demonstrate how the environment can alter the activity of genes. Whereas the structure or sequence of a gene is fairly stable, the function of the gene varies over time and the course of development. It is by altering gene function through chemical modifications, known as epigenetic marking, that environment exerts its influence on genes while leaving the genes’ essential structure intact."
Keep in mind when they talk about environment, they're not talking about medical intervention such as vaccines. Environment refers to daily exposures, such as the example given.
" A disease can be caused by a mutation in one or several genes yet be sporadic. In such cases, the mutations just happen—often as a result of mistakes during routine copying of DNA as sperm or eggs are produced. Such mistakes are often, but not always, repaired by the cell. If they escape repair, the resulting mutations are said to be de novo (or new) because they were not inherited from the parental generation, and they may cause disease in the offspring in ways that cannot easily be predicted. By contrast, mutations that lead to well-recognized Mendelian genetic disorders, such as sickle cell anemia, cystic fibrosis, or Huntington’s disease, are typically inherited from one or both parents and often lead to distinctive and predictable disease patterns in families."
That oughtta help anti vaxxers understand the difference.