John Snow’s work on cholera was important in changing attitudes towards disease and helped move away from the miasma theory. However, its impact was limited at the time, and other developments like Jenner’s vaccination, Pasteur’s germ theory, and government action had a greater long-term influence on the prevention of infectious diseases. Therefore, while Snow’s work was significant, it was not the main turning point in the period 1700–1900. John Snow’s investigation into the 1854 cholera outbreak in Soho was an important moment in public health. He mapped the deaths and found they were all linked to one water source: the Broad Street pump. When the handle was removed, the outbreak ended. This was significant because it directly challenged the miasma theory, which claimed that disease was spread through “bad air.” Snow provided clear evidence that cholera was waterborne, showing that a contaminated pump could be the source of the disease. His work also introduced a more scientific, observational approach to public health, using maps and data rather than simply relying on long-held beliefs. Although Snow couldn’t prove why water caused cholera — as germs hadn’t yet been discovered — he played a key role in questioning existing ideas and moving medicine toward a new way of thinking. Despite the accuracy of Snow’s conclusions, his work did not have an immediate effect on public health at the time. The medical community and government largely ignored his findings, partly because he could not explain the scientific cause of cholera. The germ theory had not yet been published, so people found it hard to believe that something invisible in the water could cause disease. Snow published his work in On the Mode of Communication of Cholera in 1855, but it failed to convince most doctors. It was only after Louis Pasteur’s germ theory in 1861 and Robert Koch’s identification of the cholera bacteria in 1883 that Snow’s ideas were accepted. Therefore, his work was ahead of its time and important in retrospect, but not a turning point by itself in the short term. In contrast, Edward Jenner’s development of the smallpox vaccine in 1796 had a more immediate and widespread impact on disease prevention. Jenner discovered that people who caught cowpox did not get smallpox. After successfully testing this theory, he developed a vaccine that quickly gained popularity. Although he couldn’t explain how it worked, the vaccine was effective in reducing the spread of a deadly disease. Importantly, the British government began supporting his work, making vaccination against smallpox compulsory in 1852. This was a crucial step in government involvement in public health. Jenner’s work was widely accepted and led to a decline in smallpox deaths. This shows that a turning point in prevention had already occurred before Snow’s cholera work, and with more visible, positive results. The most significant turning point in the prevention of infectious diseases came with the germ theory, developed by Louis Pasteur in 1861. Pasteur proved that microorganisms caused decay and disease, completely overturning the miasma theory. This breakthrough provided the missing explanation that Snow had lacked. Following this, Robert Koch identified the specific bacteria behind many diseases, including cholera in 1883 and tuberculosis in 1882. These scientific discoveries enabled doctors and governments to understand how to truly prevent disease — by targeting the germs themselves. This understanding led to huge improvements in hygiene, the development of new vaccines, and the enforcement of major public health reforms such as the Second Public Health Act of 1875. Unlike Snow’s work, these discoveries had immediate impact and global influence, marking a true turning point in medical science and disease prevention. While John Snow’s work was important in challenging existing beliefs and identifying contaminated water as a source of cholera, it did not lead to significant change until later developments supported it. His findings were not accepted until Pasteur and Koch provided the scientific proof behind germ theory and the causes of disease. In contrast, Jenner’s vaccine had immediate and practical results, and germ theory revolutionised the way diseases were prevented and treated. Therefore, Snow’s work contributed to progress, but it was not the main turning point in the prevention of infectious diseases between 1700 and 1900. The true transformation came from scientific discovery and government action in the later 19th century.