Vaccination is effective in preventing serious diseases (see table: number of cases to some diseases that are preventable by vaccination). Given their low cost (especially compared to medications that need to be taken long-term) Vaccines are one of the most cost-effective drugs. Vaccines are so effective that many practicing physicians today have experienced few or no cases of diseases that were once very common and deadly. Since the diseases prevented by vaccines are typically become so rare in the US and because vaccines are given otherwise healthy children, vaccines are required to have a high safety profile. Number of cases to some diseases that are preventable by vaccination disease Average number of cases per year before the vaccine development (20th century) cases in 2010 (2008) Diphtheria 21,053 0 Haemophilus influenzae type B 20,000 (estimated) 270 Hepatitis A 117,333 (11,049) Hepatitis B (acute) 66,232 (11,269) 61 503 217 measles mumps, pertussis 162 344 2,528 200 752 21 291 pneumococci (invasive, all age groups) 63,067 (44,000) Pneumococcal (invasive, <5 years) 16,069 (4,167) polio (paralytic) 16,316 0 rotavirus (hospitalizations <5 years) 62,500 (7,500) 47,745 rubella smallpox 6 29005 0 Tetanus 580 8 varicella 4,085,120 (449,363) Adjusted to Appendix G: Data and statistics: Impact of vaccines in the 20th and 21st centuries. In Epidemiology and Prevention of Vaccine-Preventable Diseases: The Pink Book, ed 12. Centers for Disease Control and Prevention, 2012. Available on http://www.cdc.gov/vaccines/pubs/pinkbook/downloads/appendices/G. /impact-of-vaccines.pdf. Before admission vaccines (such as any medical device) in randomized controlled trials (RCTs) that compare the new vaccine with a placebo (or with a previously vorfügbaren vaccine if one exists) tested. Such randomized controlled studies prior to licensing are primarily designed to evaluate the efficacy of the vaccine and to identify the most common adverse side effects (eg. As fever, local reactions at the injection site, such as redness, swelling and pain). However, some side effects are too rare in order to be detected at any convenient size in a randomized controlled trial, and can possibly only after taking a vaccine occur in routine use. Therefore, two monitoring systems, the Adverse Event Reporting System (VAERS-s. VAERS) and Vaccine Safety Datalink (VSD s. CDC VSD program) created to monitor the safety of vaccines after licensing. VAERS is a security program that is jointly owned by the FDA and the Centers for Disease Control and Prevention (CDC) sponsored; VAERS collects reports of individual patients who believe they have a side effect after a recent vaccination. Health workers must also report certain events after vaccination and report events possibly even if they are not sure if they are related to the vaccination. VAERS reports come from all over the country and provide a quick assessment of the potential security issues. However, VAERS reports can only show temporal associations between vaccination and the suspected side effect; they show no causal relationship. Therefore VAERS reports must be assessed using other methods. One such method utilizes the VSD, the data from nine large managed care organizations (MCOs), which cover more than 9 million people use. The data includes the administration of the vaccine (in the patient's file as part of the routine care indicated) and the subsequent medical history including side effects. Unlike VAERS VSD comprises data from patients who have received a particular vaccine and those who did not receive him. Therefore VSD can help to differentiate actual side effects of symptoms and disorders that are randomly occurred after vaccination, and thus to determine the actual incidence of side effects. For certain side effects of certain vaccines, case numbers to some diseases that are preventable through vaccination.