Last week, normal immune function and how vaccines work were discussed. Before vaccines, the only way to become immune to a disease was to survive having it, a process known as “natural immunity”. In the process of developing natural immunity, however, symptoms of the disease, along with its potential complications, were experienced. Immunity developed through immunization is called “acquired immunity”. The benefits of developing immunity in this manner include not having to suffer the symptoms of the disease along with avoiding the risk of passing the disease on to someone else.
Here are four examples of the ways in which disease morbidity and mortality have been affected since the advent of immunizations:
- Polio—Prior to development of the polio vaccine, as many as 20,000 cases of paralytic polio occurred each year in the U.S. These epidemics left many of its victims, mostly children, with life-long disabilities and as well as causing deaths. Thanks to immunization programs, polio has essentially been eradicated in the United States. Worldwide, cases have decreased from around 350,000 in 1988 to fewer than 200 cases in 2012.
- Haemophilus Influenzae Type b (Hib) infections—The Hib bacteria caused approximately 20,000 cases of meningitis, pneumonia, or upper airway infection (epiglottitis) annually before the vaccine was introduced. As many as 600 children died of Hib meningitis each year, and those who survived often had deafness, seizures, or mental retardation. Since Hib immunization has become commonplace, rates of Hib infections have decreased by 98%.
- Hepatitis B—Up to 5% of Americans have been infected with the Hepatitis B virus. Most of these cases resolve on their own, however, a certain percentage of those infected will develop chronic infection capable of being passed on to others. The Centers for Disease Control (CDC) estimates that there are currently between 800,000 and 1.4 million Americans with chronic hepatitis B. These individuals are at increased risk for developing liver cirrhosis, liver failure, and liver cancer. Fortunately, the incidence of new infections has decreased from an average of 450,000 in the 1980s to an estimated 18,800 in 2011. The greatest decline has occurred among children and adolescents due to routine hepatitis B vaccination.
- Rubella—Not normally a serious illness in children, its chief danger is the likelihood that a woman contracting Rubella during pregnancy could pass the infection to her developing fetus. Along with the risk of miscarriage and premature birth, children born with Congenital Rubella Syndrome (CRS), may suffer from a wide range of birth defects, including deafness, eye defects, heart defects, and mental retardation. In the mid-1960’s, prior to the development of an effective vaccine, a Rubella epidemic occurred in the U.S. During that epidemic, around 2,000 neonatal deaths were attributed to Rubella and 20,000 children were born with CRS. Of these, 11,000 were deaf, 3,500 blind, and 1,800 mentally retarded. Fortunately, vaccination programs have essentially eliminated Rubella infections and the risk of CRS in the U.S.
Similar dramatic decreases in the rate of occurrence, morbidity and mortality due to immunizations can be presented for other diseases including Tetanus, Mumps, Varicella (Chickenpox), Smallpox, Pertussis (whooping cough), Diphtheria, and Influenza. In addition to protecting yourself, vaccines can protect others. Once immunized, you are prevented from contracting the illness, which will also keep you from passing it on to someone else.
Should immunization rates drop, however, the likelihood of an outbreak increases. Recently, the California Department of Health announced that infections with Pertussis, commonly known as “whooping cough”, have reached epidemic proportions. As of this writing, over 4,500 cases of Pertussis with three deaths have been reported. This epidemic developed despite the availability of an effective vaccine available since the 1940’s. Although it is too early to say exactly why this outbreak has occurred, it is speculated that it may be related to parents who opted to not have their children immunized.
Many diseases with low rates of occurrence in the U.S. continue to occur in other countries. For example, Polio, which has been eradicated in this country, still occurs in Afghanistan, Nigeria and Pakistan. World-wide, around 100,000 cases of Rubella were reported to the World Health Organization in 2012. A similar number of cases of CRS are estimated to occur each year, primarily in developing countries. It is important that immunization programs continue in this country in order to keep diseases that are no longer common from re-establishing a foothold.
There is no denying that vaccines are capable of causing side effects. The facts show, however, that the overwhelming majority of these are minor and transient. In regard to the population as a whole, the benefits that immunizations have produced far exceed any recognized complication that they may have caused.
Clarification: Following last week’s Health Tip, a reader pointed out ongoing ethical concerns regarding certain vaccines, in particular, the Rubella vaccine. While it is true that “aborted fetuses” are not currently being used to manufacture vaccines, the original Rubella vaccine was developed, and continues to be produced, using a human cell strain (WI-38) obtained from an aborted fetus whose mother had been infected with the Rubella virus. Certain groups oppose the use of this vaccine primarily due to issues concerning the sanctity of life. For more information on the development of Rubella vaccine and ethical concerns regarding its use, see the link on Human Cell Strains in Vaccine Development from the “History of Vaccines”, a project of the College of Physicians of Philadelphia.