Scott, Shelby R. M.D., FACSM, FAAFP
Vaccination is very important for public and personal health. The efficacy of immunization (IZ) programs is demonstrated by the decrease in death caused by preventable diseases. Since the advent of the mumps-measles-rubella IZ, there has been a 99.9% reduction in these reportable diseases (17). In 2006, there were only 66 reported cases of measles or rubella in the United States. Other diseases reflect similar statistics; tetanus disease has decreased by 93% since the institution of the vaccine (11), and the number of pertussis cases has decreased by 92% (12). Newer vaccines have similar efficacy. The relatively recently introduced vaccines for chickenpox (varicella) and hepatitis A have resulted in more than 85% reduction in disease burden (1,4). The success of these vaccines is caused largely by the childhood IZ programs, with IZs required for school entry. Because most parents comply with IZ recommendations, most children have immunity to the diseases, reducing the chances of an epidemic even if one child contracts the illness. IZ programs also have lowered the rate of virulent infections (9). Recent outbreaks of preventable illnesses have occurred because not all immunity from IZs is lasting (1,9).
To continue disease prevention with passive immunity, people need booster shots to maintain antibody levels. The national goals of Healthy People 2010 include reduction of vaccine-preventable disease in adults as well as in children. Specific goals directed at adults include elimination of diphtheria, measles, mumps, rubella, and tetanus, at least a 75% reduction in the number of cases of hepatitis A and B, and 90% compliance with routine administration of pneumococcal and influenza vaccines (2).
Between 1970 and 1990, the number of cases of pertussis in the United States was negligible. After 1990, the number started creeping up, mostly related to illness in young adults, with more than 25,000 cases documented in 2005. In response to this increase, a new vaccine was designed to boost adult pertussis immunity at the same time the tetanus booster is given. This new vaccine has been available since 2005 for adults and is recommended once during adulthood in the place of the regular tetanus booster. As a result, the number of cases of pertussis is declining again (12). The regular interval between tetanus shots is 10 years, but if it was given without the pertussis, as often happens in the urgent or emergent care situations, the tetanus with pertussis can be given 2 years later. All high school-aged kids should have the tetanus-diphtheria-acellular pertussis vaccine. In addition, all health care personnel and adults working with children younger than 1 year need the new vaccine. Pertussis can cause a severe illness in susceptible people, but cases in young adults are mild, facilitating the spread of disease.
In contrast, tetanus is relatively rare in the United States. There were 41 cases of tetanus-related illness and one death in the United States in 2006. The rate is estimated at 1,000,000 cases annually in developing countries. A tetanus booster is recommended every 10 years for teens and adults. The vaccine is 95% effective in adults at reducing or preventing disease, but the prevalence of disease is seven-fold higher in the older-than-60-years population, demonstrating a lack of lasting immunity. There are very few reasons to withhold tetanus vaccinations from adults, and most received similar IZ during childhood (Table 1) (3,4,13). This includes vaccination during pregnancy (Table 2) (3,4,7).
Chickenpox (varicella) is thought of as a childhood disease with minimal adverse effects. The disease has had serious financial impact in man-hours lost to the disease for both illness and child care. In addition, only 2% of the cases before the vaccine occurred in adults, but 50% of fatalities occur in this population, with 0.41 deaths per million people per year (5). Since the advent of the varicella vaccine, the mortality has decreased more than 65% (1). There is a clear benefit to vaccination in all people younger than 50 years if they have not had the nascent disease. It is currently recommended for all health care workers and all people caring for the elderly or children younger than 1 year. The overall incidence of chickenpox decreased 80% the first 10 years the vaccination was approved for use. The initial recommendation was for a single dose of vaccine. However, the incidence of chickenpox in vaccinated children increases after 5 years. For this reason, a second booster shot is now recommended (13).
A new vaccine can be offered to people older than 60 years to prevent shingles (herpes zoster) and, hence, the complication of postherpetic neuralgia (PHN). The vaccine is very safe and can be given to people who have had shingles. It is indicated in elderly with a history of chickenpox and immunosuppression. The vaccine can reduce the risk of PHN four-fold (1,14).
Despite the proven efficacy of vaccination, many adults continue to refuse IZs. Even health care workers are underprotected (10). The populations most in need of influenza IZ are outlined in Table 3 (6,13). People have many excuses why they do not want the flu shot. The most often cited is "I got the flu shot last year, and I got sick." The pandemic of H1N1 (swine flu) in 2009 shows the flu IZ does not confer immunity to all different types of flu in any year. The flu vaccine is developed based on the three types most likely to cause severe illness in the upcoming flu season based on last year's disease patterns. In addition, because the vaccine is offered at the beginning of the flu season, most people are likely to contract some form of flulike illness in the months after their IZ. Proper education and counseling can overcome the fear of getting sick from the flu shot.
The H1N1 pandemic may boost compliance with flu vaccination even though the immunity to other forms of influenza does not confer immunity to the H1N1 virus. Currently, a vaccine for H1N1 virus is being tested in human volunteers (16). Individuals may require more than one injection of the H1N1 vaccine because they do not have preexisting antibodies. The seasonal and pandemic influenza vaccines are being produced as separate preparations, and whether it will be possible to administer them together is unknown. In 2009, the flu season extended well past winter months for many different influenza viruses. Fortunately, school breaks and a decline in airline travel have helped to slow the spread of H1N1 and other flu viruses.
One fear about a swine flu vaccine was the associated increase in Guillain-Barré syndrome (GBS) seen with the vaccine in 1976 to 1977 (8). The incidence of GBS has decreased since 1990. Flu vaccine is cultured on chicken eggs, and chickens carry Campylobacter, which is known to cause GBS. The rate of Campylobacter infection is very low now, thanks to food safety guidelines. In 1990, the U.S. Centers for Disease Control started compiling information about reactions to vaccinations. The Vaccine Adverse Event Reporting System is just that; it is a reporting system for any event temporally related to vaccination. It is important to note that reporting does not prove causality. Since its inception, only 501 cases of GBS have been reported with flu IZ. The current incidence of GBS is 0.04 per 100,000 flu vaccinations (8).
There has been some question about a relationship between childhood vaccinations and autism. No causal relationship has ever been determined. A similar concern has been expressed between adult vaccinations and myocardial infarction and stroke. However, there is no increase in risk of acute coronary events or stroke after vaccination for flu, tetanus, or pneumococcus. In contrast, the risk increases almost five-fold after a lower respiratory tract infection such as bronchitis or pneumonia (15).
Although vaccines are very safe, all vaccines have mild to moderate adverse reactions. Reactions to tetanus-diphtheria such as a severe allergic reaction, generalized hives and itching, and angioedema have been reported. Some people develop arthralgias, or swollen joints, with this vaccine. These people have high serum antitoxin levels and should be instructed to avoid booster doses more often than every 10 years. Approximately one third of persons who receive pneumococcal vaccine develop mild local side effects such as pain, redness, or swelling at the injection site. More serious reactions such as fever or body aches are rare. The varicella vaccine is very well tolerated. When the vaccine was first marketed, there were 16,683 reports of vaccine reaction voluntarily reported worldwide at a rate of 3.4 reports per 10,000 doses of vaccine. Pain and redness at the injection site and fever have been the most common adverse events reported. There have been three laboratory-confirmed cases of meningitis in children caused by the varicella vaccine, including one immunocompetent child. Of the events reported, there were 3,192 people with rashes, half of which were vesicular (chicken pox) in nature. Further studies showed that some of the rashes were a result of exposure to wild chickenpox and not the vaccine. Recipients who develop a rash may shed live virus, placing close contacts at risk for illness.
Severe allergic reactions to vaccines are rare but can be life threatening. Severe reactions are true allergy immunoglobulin E-mediated reactions. They are usually reactions to vaccine components and not the microbial products. There have been reports of allergic reactions to nearly every vaccine, but the most common are yellow fever, mumps-measles-rubella, tetanus, Japanese encephalitis, and human papillomavirus. Evaluation of a possible vaccine allergy should be performed by allergy specialists. The skin prick method is usually used. If the suspect vaccine contains egg, chicken, or gelatin proteins, skin testing to these constituents also should be performed (see Table 1). If skin testing with the vaccine is negative, the patient can receive the vaccine in the usual manner but under the supervision of the allergy specialist.
In summary, vaccines are very safe and shown to reduce both morbidity and mortality compared with natural diseases. All health care workers and people who work with kids need to be vaccinated against any disease that they have not had, according to Advisory Committee on Immunization Practice guidelines. Most adults are not current on their vaccinations, despite the well-documented efficacy of vaccination. The risks are minimum, and very few people have true contraindications to vaccination (Table 1). To protect you, your family, and your coworkers, discuss what IZs might benefit you at your next doctor visit.
1. Albrecht MA, Hirsch MS, McGovern BH. Prevention of varicella-zoster virus infection [Internet]. 2009 [cited 2009 July 1]. Available from: http://www.uptodate.com/online/content/
. Last updated April 9, 2009.
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. Guillain-Barré syndrome following influenza vaccine. JAMA
12. Kretsinger K, Broder KR, Cortese MM, et al.
Preventing tetanus, diphtheria, and pertussis among adults: Use of tetanus toxoid, reduced diphtheria toxoid and acellular pertussis vaccine. Recommendations of the Advisory Committee on Immunization Practice (ACIP), and recommendations of the ACIP supported by the Healthcare Infection Control Practices Advisory Committee (HICPAC) for use of Tdap among health care personnel. MMWR Recomm Rep
13. Kroger AT, Atkinson WL, Marcuse EK, Pickering LK. General recommendations on immunization: Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Morb Mortal Wkly Rep
14. Oxman MN, Levin MJ, Johnson GR, et al
. A vaccine to prevent herpes zoster and postherpetic neuralgia in older adults. N Engl J Med
15. Smeeth L, Thomas S, Hall AJ, et al
. Risk of myocardial infarction and stroke after acute infection or vaccination. N Engl J Med
17. Watson JC, Hadler SC, Dykewicz CA, Reef S, Phillips L. Mumps, measles, and rubella - Vaccine use and strategies for elimination of measles, rubella, and congenital rubella syndrome and control of mumps: Recommendations of the Advisory Committee on Immunization Practice (ACIP). MMWR Recomm Rep