Prevention of Infectious Disease

Preventive medicine can be categorized as primary, secondary, or tertiary. Primary prevention aims to remove or reduce disease risk factors (eg, immunization, giving up or not starting smoking). Secondary prevention techniques promote early detection of disease or precursor states (eg, routine cervical Papanicolaou screening to detect carcinoma or dysplasia of the cervix). Tertiary prevention measures are aimed at limiting the impact of established disease (eg, partial mastectomy and radiation therapy to remove and control localized breast cancer). Table 1–1 gives data for deaths from preventable causes in the United States. Table 1–2 compares recommendations for periodic health examinations as developed by the United States Preventive Services Task Force, the American College of Physicians, and the Canadian Task Force on the Periodic Health Examination. Despite emerging con ensus on many of the services, controversy persists for others.

Many effective preventive services are underutilized. In 2006, the National Commission on Prevention Priorities ranked clinical preventive service recommendations up to December 2004. The three highest-ranking services were discussing aspirin use with high-risk adults, tobacco-use screening and brief interventions, and immunizing children. Other high-ranking services with data indicating low current utilization rates (< 50%) included screening adults aged 50 and older for colorectal cancer, immunizing adults aged 65 and older against pneumococcal disease, and screening young women for Chlamydia sures—especially immunization, improved sanitation, and better nutrition.

Immunization remains the best means of preventing many infectious diseases. In the United States, childhood immunization has resulted in near elimination of measles, mumps, rubella, poliomyelitis, diphtheria, pertussis, and tetanus. Haemophilus influenzae type b invasive disease has been reduced by more than 95% since the introduction of the first conjugate vaccines. However, substantial vaccine-preventable morbidity and mortality continue to occur among adults from vaccine-preventable diseases, such as hepatitis A, hepatitis B, influenza, and pneumococcal infections. For example, in adults in the United States, there are an estimated 50,000–70,000 deaths annually from influenza, hepatitis B, and invasive pneumococcal disease. In 2002, only about 65% of elderly persons reported receiving influenza and pneumococcal vaccines. It has been documented that annual influenza immunization with inactivated vaccine (administered intramuscularly) prevents cardiovascular morbidity and all-cause mortality in persons with coronary and other atherosclerotic vascular disease. However, immunization with live, attenuated vaccine (administered intranasally) is contraindicated for such persons.

The American College of Physicians recommends that clinicians should review each adult’s immunization status at age 50; assess risk factors that would indicate a need for pneumococcal vaccination and annual influenza immunizations; reimmunize at age 65 those who received an
immunization against pneumococcus more than 6 years before; ensure that all adults have completed a primary diphtheria-tetanus immunization series, and administer a single booster at age 50; and assess the postvaccination serologic response to hepatitis B vaccination in all recipients who have ongoing risks of exposure to blood or body fluids (eg, sharp injuries, blood splashes). Recently, strategies have also been proposed to improve influenza, pneumococcal polysaccharide, and hepatitis B targeted vaccination; in other words, improve coverage among those adults aged 65 years or younger who are at high risk for exposure or disease. Strategies to enhance vaccinations in general include increasing community demand for vaccinations; enhancing access to vaccination services; and provider- or system-based interventions, such as reminder systems. Clinicians can substantially improve immunization rates by use of standing orders and algorithms, expanded nurse decision-making, patient education and incentives, and partnership with community pharmacies. Increasing reports of pertussis among US adolescents, adults, and their infant contacts have stimulated vaccine development for older age groups. A safe and effective tetanus-diphtheria 5-component acellular pertussis vaccine (Tdap) is now available for use in adolescents and adults. On October 26, 2005, the Advisory Committee on Immunization Practices (ACIP) recommended routine use of a single dose of Tdap for adults
aged 19–64 years to replace the next booster dose of tetanus and diphtheria toxoids vaccine (Td). The ACIP also recommended Tdap for adults who have close contact with infants younger than 12 months, for pregnant women, and women who are planning a pregnancy.

Recommended immunization schedules for children and adolescents and adults are set forth in Tables 30–12 and 30–13. Thimerosal-free hepatitis B vaccination is now available for newborns and infants. Human papillomavirus (HPV) virus-like particle (VLP) vaccines have demonstrated effectiveness in preventing persistent HPV infections, and thus may impact the rate of cervical intraepithelial neoplasia II–III. Results from one randomized controlled trial of HPV16 L1 VLP vaccine showed that it provided high-level protection against persistent HPV16 infection and HPV16-related CIN II–III for at least 3.5 years after immunization.