Infectious Diseases in the Pre-Vaccination Era
Global life expectancy at birth, ~28.5 years in 1800 and ~31 years in 1900, increased over the past two centuries in the developed world, and over the past 50 years in the developing world, almost exclusively as a result of reduced mortality from infectious diseases. This became possible as a result of improved sanitation, the discovery of antibiotics, and vaccination (Bonanni, 1999; Riley, 2005).
During the second half of the 19th century, 100 to 350 infant deaths per 1000 live births occurred in the United States and Western Europe, and about 40-50% of the infant deaths between 1870 and 1900 in the United States were caused by infectious diseases (Lee, 2007). A drastic decline in infant mortality during the late 19th century and early 20th century in the United States and Western Europe resulted mostly from a decrease in infectious disease-related deaths and improved nutrition (Lee, 2007).
In the years preceding the vaccination era, between 1783 and 1800, 50% of children in Glasgow died before reaching age 10, and 40% of those deaths were caused by smallpox, which at the time was the leading cause of blindness in Europe (Henderson, 1997).
National statistics from several European countries, including England, Norway, and Sweden, reveal that smallpox directly caused 8-20% of all deaths during the 18th century, in addition to increasing the risk of death from other causes (Bonanni, 1999). No treatment exists for the infection, which presented with febrile prodrome and a generalized vesicular/pustular eruption with lesions at the same stage of development on any body part (Figure 1). When the World Health Organization (WHO) global vaccination campaign started in 1967, smallpox was still causing 10 to 15 million infections annually, and ~30% of those infected died (Bean, 2011).
Between 1922 and 1931, ~1.7 million cases of pertussis (whooping cough) caused 73,000 deaths in the United States, as compared to a more recent 10-year period from 1983 to 1992, when slightly over 34,000 cases claimed 56 deaths (Cherry, 1999). In Japan, where the triple diphtheria, pertussis, and tetanus (DPT) vaccine was introduced in 1947, the number of whooping cough cases decreased from 100,000, and 15,000 deaths, to <300 and no deaths in 1974. After a national debate over the DPT vaccination led to its replacement with the bivalent diphtheria and tetanus (DT) vaccine, the incidence of pertussis started to increase, and a 1979 outbreak caused 13,000 infections and 41 deaths (Amanna & Slifka, 2005).
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Poliomyelitis, an infectious disease that has existed since antiquity, caused annual outbreaks in the United States from the early 1900s until 1955 when the first vaccine, the inactivated poliovirus vaccine (IPV), also known as the Salk vaccine, was introduced (Salk et al., 1954; De Jesus, 2007). In 1988, approximately 1000 children worldwide were still becoming paralyzed by polio every day (WHO; Heymann & Aylward, 2006). As a result of the Global Poliomyelitis Eradication Initiative, launched in 1988 by the WHO together with Rotary International, U.S. Centers for Disease Control and Prevention (CDC), and UNICEF, the number of recorded poliomyelitis cases decreased worldwide from 350,000 in 1988 to <20,000 in 1999 and to 680 in July 2006. The number of endemic countries decreased from 125 in 1988 to 30 by late 1999, and in 2008 only four countries, Afghanistan, India, Nigeria, and Pakistan, reported the infection (Hull & Aylward, 2001; Dutta, 2008). Polio vaccination reduced the annual number of paralytic polio cases in the United States from 10,000 to approximately 10 (Nathanson & Martin, 1979). The fact that not more than 90% of the children in the United States were immunized indicates that either the vaccine spread to those unimmunized and conferred protection, or that herd immunity limited the spread of the virus through the population and eventually prevented infection even among those who were not immunized (Nathanson & Martin, 1979). …