The baby's mother had trouble with her breast milk supply, and the parents who were strict vegans opted to supplement with soy milk and apple juice instead of infant formula. They were convicted of murder. Soy milk and apple juice are not suitable breast milk replacements, but how about so-called vegan formula?
The above case is not the only similar one. The Food and Drug Administration investigated two cases where parents fed vegan formula brands instead of conventional formula in 1990. In both cases, the babies were hospitalized and suffered malnutrition. They used two brands of vegan formula, EdenSoy and SoyMoo respectively. After that, the FDA issued warnings on these types of formula. Soy formula also caused the death of three babies in Israel in 2003, and resulted in brain damage for at least four others.
The manufacturer of the formula these parents were using did not have adequate nutrients, something that was not mentioned on the label. Vegan formula, clearly, is not nutritionally adequate for babies at all. Vegans consider breast milk to be vegan (it is freely given, not by coercion!) but soy formula and equivalents are not alternatives to breast milk.
Babies need vitamins, minerals, fatty acids and amino amino acids, that is not available through these types of formula. Vegans who feel strongly about using no animal products can look for donor milk. Babies that have allergies like lactose intolerance should be put on special formula in agreement with the baby's pediatrician.