In and of itself the act of vomiting is not likely the issue, resultant dehydration and/ or nutrient deficiencies and/ or systemic inflammation can be. But understand the hair doesn't shed right away, it goes into a dormant state and sheds weeks or months later. This means shedding can continue long after the health problem is resolved which is obviously distressing. So the faster you identify and address any dietary issues the less hair you are likely to lose.
Shedding is not more common in humans in the summer it's more common in the autumn/ winter, we don't moult like cats or dogs. If it's not normal for you, it's not normal for you.
I do feel for you, a dear friend of mine had hyperemesis badly enough to be hospitalised with dehydration.
2a-2c, medium texture, porous/ colour treated. Three years CG, growing out mechanical and chemical damage = breakage and very high porosity. Past armpit length heading for waist.
Treatments: Komaza protein, Komaza Matani, coconut oil with sugar syrup. Hairveda Sitrinillah
Leave in: Fructis Sleek & Shine (old), Gliss ultimate volume
Styler: Umberto Giannini jelly, Boots curl creme, Rockin RInglets
Experimenting with: Mega-Tek, Curl Harmony reviver, Elvive Full Restore 5.