I did a study where I searched in the individual yearly PDF's of the Golden Age / Consolation / Awake, or I searched in the 2015 Watchtower Library, for the following terms:
I did not discriminate between positive and negative mentions of the terms.
For "Aluminum" I actually searched for "Alumi" and Adobe would search for words that started with that.
For "Vaccines" I actually searched for "vacc". I searched for "serum" for the serum search, but in the years 1940 and up I had to be careful that they were talking about vaccines and not blood transfusions when the term "serum" was used.
For "transfusions" I actually searched for "transfu".
For "transplants" I actually searched for "transpl" and made sure that organ transplants were being discussed and not plant transplantation.
Some interesting facts:
In 1934, the word "aluminum" was mentioned a whopping 436 times, this is 100 times more the average mention in the years 1970-2015.
In 1921, the word "vaccine" was mentioned MORE than the word "Jehovah"... 149 vs 132 times.
Here are the graphs: