![]() In contrast, other live, attenuated vaccines such as the oral polio vaccine (OPV) and the first licensed vaccine against rotavirus (RotaShield®) serve as important reminders that vaccines must be safe if they are going to be used successfully for routine vaccination. Some of the best examples of successful live, attenuated vaccines include those developed against measles, mumps, and rubella (MMR). The smallpox vaccine is not only the first vaccine ever developed ( Jenner 1798, 1799, 1800), but since Variola virus (the causative agent of smallpox) no longer exists in nature, this also represents the first example in which a vaccine was purposefully used to drive a species to extinction. Smallpox vaccination with vaccinia virus is the most famous example of a highly effective vaccine and at the time when people were faced with smallpox outbreaks, this vaccine was associated with each of these characteristics that led to the implementation of a successful vaccine. Development of successful vaccines is typically easier when there is (a) a single serotype, (b) the pathogen is antigenically stable, (c) diagnostic tests/clinical criteria for measuring disease burden are available, and (d) the vaccine is both safe and effective. There are currently 13 diseases for which live, attenuated vaccines have been developed and licensed for commercial use ( Table 1). Interestingly, influenza represents the only example in which there is at least one licensed vaccine listed in each of these three categories.Ģ. Successes and failures of live attenuated vaccines There are similar numbers of licensed vaccines in each of these categories ( Table 1) and this illustrates the point that no single vaccine approach is superior to another, but instead the approach varies according to each individual pathogen and the feasibility, safety, and efficacy required to develop a successful vaccine to that particular pathogen. Most licensed vaccines can be categorized as (a) live, attenuated vaccines, (b) non-replicating whole-particle vaccines (including virus-like particles, or VLPs), and (c) subunit vaccines. ![]() There are vaccines against bacterial toxins (e.g., tetanus and diphtheria toxins), acute viral pathogens (e.g., measles, mumps, rubella), latent or chronic viral pathogens (e.g., varicella zoster virus and human papilloma virus, respectively), respiratory pathogens (e.g., influenza, Bordetella pertussis), and enteric pathogens (e.g., poliovirus, Salmonella typhi). Vaccines have been developed against a wide assortment of human pathogens ( Table 1). Among 73 nations supported by the GAVI alliance, mathematical models project that vaccines will prevent 23.3 million deaths from 2011–2020 compared to what would have occurred if there were no vaccines available ( Lee et al. One study examining the impact of childhood vaccination on the 2001 US birth cohort found that vaccines prevented 33,000 deaths and 14 million cases of disease ( Zhou et al. The effect of vaccines on public health is truly remarkable.
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