Several early Nobel Prizes were given for discoveries that led to the development of vaccines for prevention of infectious diseases. The irony is that these diseases were already in steep decline in terms of incidence and deadliness, even before there were broad public health measures to get the masses vaccinated.
See for example pubic health data on pertussis (whooping cough) in the graph above. Pertussis is a disease that tends to affect children. It is caused by a bacterium that releases a toxin, which damages the tiny sweeping hairs that coat the lining of the lungs. This results in swelling and pain in the throat and air passages with frequent coughing spells to expel mucus. The coughing can last for weeks – the Chinese call it “hundred-day cough.”
The treatment is antibiotics if it is diagnosed early. If symptoms have been going for three weeks or longer, antibiotics are not given because although the cough may persist, the body has cleared the bacteria by its own immune mechanisms. In 1838, the death rate from pertussis ranged between 40 and 60 per population of 100,000. Death rates from pertussis stayed about the same until 1880. For reasons unknown, the death rate began a remarkable decline at that time, which continued for decades.
Just about when Nobel Prize winner Bordet and his research assistant Gengou were isolating the pertussis bacterium in their lab at the Pasteur Institute of Belgium, the pertussis death rate was continuing its steep decline: 1906 death rates were down to about 25 per 100,000.
In 1917, with the introduction of the first crude vaccine, there was a spike of increased death rates for one year, but then it resumed its downward trend. Before pertussis vaccine was introduced for wide use in America in the 1950s, the death rate was under 5 per 100,000. This tells us that pertussis was naturally becoming a less virulent, less deadly disease all on its own and completely independent of any vaccines.
There have been outbreaks of whooping cough in the United States in the last decade with pockets of one hundred to two hundred children or young adults affected in various states. Ironically, the vast majority of kids who fell ill had been fully vaccinated, but the vaccine effectiveness had worn off.