50,000 years ago, humans living in stable tribal hunter/gatherer and fishing cultures in healthy eco-systems had robust immune systems and lived long, healthy lives in tropical and sub-tropical regions. (except for higher rates of childbirth and infant mortality, the one un-equivocal "success" of contemporary medicine)
We discovered fire and invented spears using stone tools to cut and sharpen wood and 40,000 years ago started impacting our ecosphere negatively, for example extincting Woolly Mammoths in ice bound Northern regions and marsupial bear and cats in Australia. Eliminating keystone species is always a bad idea - better to have man-eaters to cull the old, slow and sick and stabilize all mammalian species.
Then we discovered seeds and started cultivating grains. This concentrated high glycemic index food source from monocropped fields caused a host of novel diseases from tooth decay to vitamin deficiencies like scurvy and metabolic disorders like diabetes - and also immuno-suppression.
The ingredients and catalysts for immune system machinery and anti-body production require a varied diet, and around five dozen bio-essential elements which enable our food chain to make vitamins, anti-oxidants, bio-flavenoids and immuno-support complexes.
Next we started supporting a ruling class living apart from the cropfields. This is called "Civilization" (making of cities). It required two innovations: food markets and sewage removal. These are found in all civilizations that grew large enough and lasted long enough to develop writing, so they constitute all of history. There are NO WRITINGS to document the healthy, happy lives of prior human culture, and few monuments.
BUT, it also imposed a limit on the duration of every civilization. Importation of food depleted the bio-essential elements from the soil, and exportation of sewage DOWNSTREAM insured these elements ended up in the ocean.
Civilizations that lasted thousands of years grew the crops in flood plains that had the elements in the soil renewed annually and anadromous fish swimming the bio-essential elements upstream against the current, but eventually became victims of their own success. As population grew, the load on the ecosystem increased from the expanding croplands, de-forestation for fuel and building materials (which also burned in city fires), and over-grazing by cloven hoofed animals that destroyed grasslands faster than they renewed.
In the last 500 years humans have expanded to all arable lands and used artificial means of irrigation to extract soil elements everywhere on Earth. The tool based trading economy meant that farmers had to sell crops to obtain clothing and metal implements - shovels, ploughs, sickles, etc. This depletes the soil slowly.
The industrialization starting 250 years ago drove rapid urbanization as towns grew up around factories and the workers were fed market crops. The soil depletion of the macro-nutrients Nitrogen, Phosphorus and Potassium caused crop yields to decline precipitously towards the end of the 19th Century, causing a boom in mining phosphate, potash and guano.
Guano was also a key ingredient in explosives, so there was a shortage during WWI which inspired chemist Fritz Haber to develop a method of extracting Nitrogen from the air. For the last 100 years, the Haber-Bosch process has driven agriculture, and now feeds 75% of humans.
BUT, chemical fertiliser collapses the bio-diversity and health of soil, and also depletes the forty odd trace elements faster because farmers are shipping more kilograms per hectare of produce to market. This reduces the health value of our food supply (already deficient because of the shift from vegetables and fruits to grains, and fresh produce to two week old food distribution).
As a result, crops lost their resistance to weeds, insects and fungi so we now need herbicides, insecticides and fungicides on the crops, which are all poisons and a lot are carcinogenic.
AND, humans are not getting the nutrition they need for a robust immune system. All of this created the NEED for anti-biotics and vaccines.
SO, when you buy your food in markets and then put your wastes in flush toilets, you are part of the vaccine conspiracy!