Online Medical Reference

Adolescent Immunization

Camille Sabella

Published: October 2013


The success of the immunization program in the United States is exemplified by the fact that vaccine-preventable diseases have been reduced by at least 95% as compared with baseline pre-vaccine morbidity. This success has been the result of the effectiveness of vaccination programs aimed at infants and children. It has become clear, however, that childhood vaccination alone does not provide sufficient protection against all vaccine-preventable diseases. Although adolescent immunizations have been recommended since 1996, the majority of adolescents in this country still lack one or more recommended vaccinations, leaving them at risk for vaccine-preventable diseases.

Vaccine coverage in adolescents is inadequate because in general they have less contact with physicians than younger children, many lack access to health care, and opportunities to vaccinate are missed by the provider. In addition, because adolescence is a time for exploration and experimentation, adolescents engage in high-risk activities that increase their risk for various infectious diseases, such as hepatitis B and human papillomavirus (HPV).

Three important infections (Neisseria meningitidis, pertussis, and HPV), for which effective vaccination now is available, are especially prevalent in the adolescent years, making the adolescent age group the ideal target age for prevention.

Recommendations regarding childhood and adolescent immunization schedules are developed collaboratively by the Advisory Committee on Immunization Practices (ACIP) of the Public Health Service, the American Academy of Pediatrics Committee on Infectious Diseases (the Red Book Committee), and the American Academy of Family Practice. A continuously updated version of the harmonized schedule is available at www.cdc.gov (opens in new tab/window). This chapter will review the most recent immunization recommendations for adolescents.

Recommended Immunizations

Conjugate meningococcal vaccine (MCV4), HPV vaccine, the adolescent preparation of tetanus and diphtheria toxoids and acellular pertussis vaccine (Tdap), and influenza vaccine are recommended for all adolescents. In addition, the adolescent years serve as a time that warrants special effort to administer those vaccines not previously administered (catch-up vaccination).

Hepatitis B

Hepatitis B vaccines in the United States are produced by recombinant DNA technology and are highly effective and safe. The strategy for prevention of hepatitis B relies on the universal vaccination of neonates and infants, so that the immunization series is complete by 18 months of age. Despite the fact that adolescents are at higher risk of infection, this strategy was chosen because neonates and infants are more likely to receive medical care. Since implementation of this strategy in 1992, the incidence of hepatitis B has dropped markedly. Adolescents who have not received the three-dose hepatitis B series remain at risk for hepatitis B infection. Those who have one or more risk factors for hepatitis B infection (Box 1) are at especially high risk. Thus, adolescents who previously have not been immunized should receive hepatitis B vaccine in a three-dose series. There is no need to restart the series for those who received one or two doses in the past. Because immune memory remains intact for 15 years or longer, a booster dose is not recommended for adolescents who have completed the three-dose series.

Box 1. Adolescents at High Risk for Hepatitis B Infection
Those who engage in injection drug use
Sexually active heterosexuals with more than one partner during previous 6 months or who have had a sexually transmitted disease
Men who have sex with men
Household contacts and sexual partners of people with chronic hepatitis B infection
Those at occupational risk of exposure to blood or blood-contaminated body fluid
Those undergoing hemodialysis
Members of household with adoptees who are chronic carriers of hepatitis B
Inmates of juvenile detention and other correctional facilities
Adolescents with bleeding disorders who receive clotting factor concentrates
Those who are long-term international travelers to areas where hepatitis B infection is endemic

Measles-Mumps-Rubella (MMR)

Approximately 95% of children immunized with the MMR vaccine at 12 to 15 months of age develop protective and durable, probably lifelong, antibodies against measles, mumps, and rubella. A second dose is recommended to protect the approximately 5% of vaccine recipients who do not respond to the first dose, and is usually given between 4 and 6 years of age. This second dose does not serve as a booster dose; rather, it is recommended to protect against primary vaccine failure, ensuring high levels of protection and thus preventing outbreaks of infection. More than 99% of patients who receive two doses of MMR vaccine separated by at least 1 month, with the first dose administered on or after the first birthday, develop immunity to measles. It is important to address the status of immunization against measles, mumps, and rubella in every adolescent to ensure that they have received two doses of MMR vaccine. Those who have not received two doses should be immunized.

Measles and mumps both occur in highly immunized populations. Periodic outbreaks of measles among adolescents continue to occur and serve to underscore the importance of ensuring that all adolescents have received two doses of this vaccine.1 Although postnatal rubella is a mild disease characterized by low-grade fever, generalized lymphadenopathy, and a discrete maculopapular rash, congenital rubella syndrome is a devastating disease, characterized by a high rate of congenital anomalies and long-term neurodevelopmental problems. Thus, emphasis must be placed on ensuring that postpubertal patients are immunized against rubella. This entails immunizing postpubertal women who do not have documentation of rubella immunity unless they are known to be pregnant, assessing postpubertal women for rubella susceptibility during health care encounters, and routine prenatal screening for rubella immunity.

Because MMR is a live virus vaccine, it should not be given to pregnant adolescents or to those who have altered immunity. Adverse effects of vaccination occurring mostly in susceptible children include rash, fever, and lymphadenopathy. Adverse reactions seen more commonly among postpubertal female vaccinees include arthralgias (25%) and transient arthritis (10%).

Varicella

Varicella vaccine was introduced in 1995 and is routinely recommended for all children. Two doses of vaccine are recommended; the first dose is administered at 12 to 15 months of age, and the second dose is given at 4 to 6 years of age. Children who are not vaccinated early in life may be vaccinated at any time. It is imperative that all adolescents be protected against varicella given the higher risk of serious illness and complications associated with varicella in adolescents and adults.

Susceptible children less than 13 years of age should receive two doses of vaccine separated by at least 3 months, whereas susceptible adolescents 13 years of age and older should receive two doses 4 weeks apart. Individuals who have a reliable history of varicella can be assumed to be immune and do not need to be immunized. Adolescents who lack a reliable history of varicella should be considered susceptible and immunized without serologic testing. This recommendation takes into account that the vaccine is well tolerated, even in immune persons, and that universal immunization of this age group is easier to implement than serologic testing and tracking of seronegative patients.

Since the introduction of the varicella vaccine and the implementation of universal immunization for all children, the incidence of varicella and its related complications and hospitalizations has dramatically declined.2,3 Because less virus is now circulating in the community, nonvaccinated children and adolescents are less likely to become infected and will be susceptible into their adult years. Thus, it is especially important to target adolescents to ensure that they are immune or have been vaccinated.

Because varicella vaccine is a live attenuated vaccine, it should not be administered routinely to adolescents with altered immunity, including T lymphocyte immunodeficiency and those receiving corticosteroid therapy (≥20 mg/day of prednisone). The vaccine should not be administered to pregnant individuals.

Hepatitis A

Hepatitis A vaccine is indicated for all children at 12 months age. Adolescents who are at increased risk of acquiring hepatitis A or at increased risk of severe disease from hepatitis A infection also should be immunized. This includes adolescents who travel internationally to areas where hepatitis A is endemic, male adolescents who have sex with men, those who use illegal drugs, those with clotting factor disorders, and those with chronic liver disease.

Hepatitis A vaccine has been shown to be safe and has a protective efficacy of 94% to 100%. Adolescents can be immunized at any age and should receive a two-dose schedule of the pediatric-adolescent formulation, with the booster dose given at least 6 months after the first dose. An adult formulation is available for those 19 years of age and older.

Influenza

Routine annual influenza vaccination is recommended for all individuals aged ≥6 months. Thus, all adolescents should be immunized annually with trivalent influenza vaccine. Particular focus should be on the administration of vaccine for adolescents who have underlying medical conditions associated with an increased risk of complications from influenza (Box 2), as well as for adolescents who have contact with high-risk persons, including children younger than 5 years. Immunization is also recommended for pregnant adolescents, which benefits the unborn infant by the transmission of transplacentally acquired antibody.

Box 2. High-Risk Conditions for Severe Influenza Infection
Asthma or other chronic pulmonary diseases
Hemodynamically significant cardiac disease
Immunosuppressive disorders or therapy
Hemoglobinopathies including sickle cell anemia
Diseases requiring long-term salicylate therapy, such as Kawasaki disease or rheumatoid arthritis
Chronic renal dysfunction
Chronic metabolic disorders such as diabetes mellitus
Human immunodeficiency virus infection
Any condition that can compromise respiratory function such as neurodevelopmental disorders, spinal cord injuries, seizure disorders or neuromuscular abnormalities

Healthy adolescents can be immunized annually with one dose of either trivalent inactivated vaccine (TIV), or a cold-adapted live attenuated intranasal vaccine. The TIV is preferred for those who have underlying medical conditions (including those with asthma), those who are pregnant, and for those who have close contact with severely immunocompromised individuals. Adolescents who have a history of egg allergy can generally be vaccinated safely. Clinicians should consult with an allergist for adolescents who have a history of severe egg allergy, defined by cardiovascular or respiratory compromise.

Meningococcal Disease

Although the annual incidence of invasive meningococcal disease in the United States is relatively low (0.5 to 1.1/100,000 population), case-fatality rates approach 10% to 14% and sequelae such as neurological disabilities, limb or digit amputation, and skin scarring in survivors are significant. Invasive meningococcal disease can manifest as meningococcemia, with relatively high mortality and morbidity rates, or as meningitis, with a lower mortality rate but a significant risk of hearing loss and long-term neurological sequelae. Because of the success of conjugate vaccines against Haemophilus influenzae type b and Streptococcus pneumoniae, Neisseria meningitidis has become the leading cause of bacterial meningitis in children.

The incidence of invasive meningococcal disease in pediatric patients has two peaks. The highest incidence is in infants younger than 12 months. A second peak occurs between 15 and 18 years of age (Figure 1).4 The overall rate of invasive disease among adolescents 11 to 19 years of age is 1.2/100,000, which is higher than that for the general population, but the case-fatality rate in adolescents is 20%, the highest of any age group. This is likely because adolescents are more likely to develop meningococcemia and to have shock at presentation.

In the United States, most cases of invasive meningococcal disease (98%) are sporadic, but the frequency of localized outbreaks, especially in schools, has been increasing over the past decade. Serogroups B, C, and Y are the major causes of meningococcal disease in this country, with each responsible for approximately one third of cases. However, the proportion of these serogroups causing disease at different age groups differs. Whereas serogroup B accounts for over 50% of cases of meningococcal diseases in infants, it accounts for less than 25% of cases in adolescents. Thus, serogroups C, Y, and W-135, for which a licensed and available vaccine exists, are responsible for 75% of cases of invasive meningococcal disease in the adolescent age group. The incidence of invasive meningococcal disease caused by these vaccine-preventable serotypes begins to increase substantially at 15 years and peaks at 18 years of age (see Fig. 1).

U.S. surveillance data on the incidence of meningococcal disease in college students has revealed that although the incidence of meningococcal disease is lower in all college students than in nonstudents, the rate of disease in freshmen students living in dormitories is significantly higher than in any other subgroup of 18- to 23-year-olds (Table 1).5

Rates of Meningococcal Disease in U.S. College Students, September 1998-August 19995
Population Rate/100,000
18- to 23-yr-old 1.4
18- to 23-yr-old, nonstudents 1.4
All college students 0.6
Undergraduates 0.7
Freshmen 1.9
Dormitory residents 2.3
Freshmen living in dormitories 5.1

Three vaccines are currently licensed for the prevention of meningococcal disease. Meningococcal polysaccharide vaccine (MPSV4) was licensed in 1981 for use in persons 2 years of age and older. This vaccine has never been recommended for routine use, but rather for those individuals who are at increased risk for meningococcal disease. Two meningococcal conjugate vaccines (MCV4) are available for use in the adolescent population. All currently available meningococcal vaccines provide protection against serogroups A, C, Y, and W-135. A vaccine that protects against serogroup B meningococcus has been developed and is currently being studied. The effects of conjugating the polysaccharide to a protein carrier allows induction of a T cell-dependent response, which in turn results in an improved primary response to the polysaccharide as well as a strong booster response on re-exposure. In addition, experience with previous conjugate vaccines has revealed that the use of these vaccines results in reduction of nasopharyngeal carriage of the organism, thus protecting nonimmunized individuals through a herd immunity effect. Therefore, the conjugate vaccines offer advantages over the polysaccharide vaccine and are preferred.

Given the epidemiology of meningococcal disease in adolescents, and the availability of a safe and effective conjugate meningococcal vaccine, all adolescents should be routinely immunized with MCV4. The vaccine should be administered routinely at the 11- to 12-year preadolescent visit. Those who are not vaccinated at the 11- to 12-year visit should be vaccinated at age 13 to 18 years.

Recent studies have documented that waning immunity occurs within 5 years of receipt of the first dose of MCV4, which correlates with an increased susceptibility to infection.4 Thus, booster doses of MCV4 are now recommended for adolescents according to the following schedule: adolescents who receive the first dose of MCV4 at 11 to 12 years of age should receive a booster dose at 16 years of age; those who received their first dose of MCV4 at 13 to 15 years of age should receive a booster dose at 16 to 18 years of age or up to 5 years after their first dose; those vaccinated with their first dose of MCV4 at or after 16 years of age do not need a booster dose.

Adolescents with HIV infection, persistent complement deficiency or anatomic/functional asplenia who have not previously been vaccinated with MCV4 should receive a two-dose primary series at least 8 weeks apart. A booster dose can be administered 5 years after the primary immunization for these adolescents.

MCV4 vaccines are well tolerated. Most reactions are mild and resolve within 3 days after immunization. A temporal association between MCV4 and Guillain Barre syndrome provoked a recommendation that adolescents with a history of GBS should not be vaccinated with MCV4. The available data to date do not support a causal relationship between MCV4 and GBS.

Pertussis

Before the availability of whole-cell pertussis vaccines in the late 1940s, pertussis was a major cause of morbidity and mortality in the United States, accounting for almost 300,000 cases and 10,000 deaths annually. Following introduction of an effective vaccine, a dramatic decrease in cases ensued and, by the early 1970s, the incidence had declined by 99% as compared with that in the prevaccine era, with a record low number of 1,010 cases reported in 1976. Since the early 1980s, however, the incidence of pertussis in this country has steadily increased (Figure 2). Although the disease is endemic, epidemic peaks occur every 3 to 5 years, and several large outbreaks in North America have been reported in the past several years. These outbreaks have occurred in highly immunized populations and in infants who had not completed their primary immunization series.6

Over the past several decades, the age distribution of pertussis has changed dramatically. In the prevaccine era, the peak incidence of disease occurred in children ages 1 to 5 years. With widespread vaccination, and by the late 1980s, infants younger than 1 year had the highest age-specific incidence, which declined with increasing age. Since the early 1990s, however, there has been a dramatic increase in reported cases in children ages 10 years and older (Figure 3). Data from the National Notifiable Diseases Surveillance System between 2001 and 2003 have revealed that children ages 10 to 19 years comprised 33% of all reported cases, whereas 23% of cases occurred in persons 20 years and older.7 During the same time period, infants younger than 1 year accounted for 23% of all cases. Infants younger than 1 year of age, however, continue to have the highest average annual incidence (55.2/100,000 population), as compared with 7.7/100,000 for persons ages 10 to 19 years and 1.1/100,000 for adults. The overall number of cases of pertussis, however, is likely underestimated, because the infection is often underdiagnosed in adolescents and adults. In 2006, over 15,000 cases of pertussis were reported; 42% of these cases occurred in the 5- to 24-year age group.

Although chronic carriage of the organism does not occur, it is clear that subclinical or mild illness commonly occurs in fully or partially immunized, as well as naturally immune, persons. This occurs because immunity wanes within 3 to 5 years of vaccination or natural infection and is often undetectable at 12 years. Thus, neither vaccination nor natural disease provides long-lasting immunity, and U.S. adults do not have adequate protection against pertussis. Importantly, adults and adolescents with pertussis serve as important reservoirs for infection and are often the index cases for younger infants and children, as illustrated during several outbreaks of pertussis over the past 2 decades.

Many studies have proven that pertussis is a common cause of prolonged cough in adolescents and adults, accounting for 12% to 32% of cases of cough lasting 2 weeks or longer. A prospective U.S. population-based study with active surveillance has revealed that 13% of study participants between the ages of 10 and 49 years who presented to their community clinic with an acute paroxysmal cough or a persistent cough illness longer than 2 weeks' duration have evidence of an acute pertussis infection. A Canadian study,8 the largest prospective study examining the rates of pertussis disease in adolescents and adults, demonstrated that 20% of 442 adolescents and adults with cough illness lasting 7 to 56 days had pertussis.

Universal immunization with pertussis vaccines for children younger than 7 years is recommended by the American Academy of Pediatrics and is the mainstay of prevention. Vaccination of all children starting in infancy has resulted in more than a 97% decrease in the incidence of pertussis in the United States as compared with the prevaccine era. The currently available acellular vaccines, which are purified subunit vaccines combined with diphtheria and tetanus toxoids (DTaP), have been shown to be 75% to 90% effective and are well tolerated.

Despite the successes of universal immunization, there continues to be a steady increase in reported cases of pertussis in this country, with resultant significant morbidity and mortality. This appears to occur because of waning immunity after vaccination and natural infection, underdiagnosis of mild disease, and infants who have not completed their primary immunization series, who remain susceptible to infection.

Because of the role that adolescents and adults play in the transmission of pertussis, the ACIP recommended that a pertussis containing vaccine combined with tetanus toxoid and diphtheria toxoid (Tdap), be used routinely in place of tetanus toxoid and reduced diphtheria (Td) vaccines in those 11 to 18 years of age (Box 3).6 This recommendation was made after a National Institutes of Health-sponsored prospective multicenter trial,9 in which 2,781 healthy subjects ages 15 to 65 years were randomized to receive acellular pertussis vaccine or hepatitis A vaccine, found that the acellular pertussis vaccine is safe, immunogenic, and effective in preventing clinical pertussis.

Box 3. Recommendations for the Use of Tetanus and Diphtheria Toxoids and Acellular Pertussis (Tdap) Vaccines in Adolescents
Single dose of Tdap instead of tetanus and diphtheria toxoids (Td) vaccine is recommended for booster immunization for adolescents 11-18 years of age.
Preferred age for Tdap immunization is 11-12 years.
Adolescents 11-18 yr of age who have received Td but not Tdap are encouraged to receive a single dose of Tdap. No minimum interval between Td and Tdap is required or advised.
Administer Tdap, conjugate meningococcal vaccine (MCV4), and human papillomavirus vaccine (HPV) during the same visit if all three vaccines are indicated.

The adolescent dose of Tdap should preferably be given at the 11- to 12-year preadolescent visit, and can be given concurrently with conjugate meningococcal and HPV vaccines. Two Tdap vaccines are currently available for use in the U.S. Although one Tdap vaccine (Boostrix) is licensed for use in the 10- to 64-year age group, and the other (Adacel) is licensed for those 11 to 64 years of age, the ACIP and AAP have recently recommended that these vaccines can and should be used for children 7 to 10 years of age who have incomplete or unknown pertussis vaccine history.10 Recent recommendations have also stated that there is no minimum interval required or advised between receipt of a tetanus toxoid- or diphtheria-toxoid-containing vaccine and Tdap when Tdap is otherwise indicated. This recommendation replaces previous recommendations that a 5-year interval between these vaccines be followed for standard use and a 2-year minimum interval for those whose potential risk for pertusssis was high. This new recommendation was made based on the fact that accumulating data did not demonstrate an increased risk of severe adverse events when Tdap was administered within a short interval from other tetanus toxoid- or diphtheria toxoid-containing vaccines. Tdap is currently recommended as a one-time dose when indicated; there are no recommendations for a booster dose of Tdap. Adolescents who have already received their dose of Tdap who require a tetanus toxoid booster should receive Td.

Human Papillomavirus

HPV infection is the cause of anogenital warts and most cancers of the anogenital tract. It is estimated that over 6 million new infections occur every year in the United States, and that 20 million persons are infected. Epidemiologic data reveal that the highest rate of HPV infection occurs in adolescents and young adults, placing women at risk of developing cervical cancer later in life.11 HPV types 16 and 18 are responsible for approximately 70% of cases of cervical cancers and types 6 and 11 are responsible for more than 90% of anogenital warts. Two HPV bioengineered vaccines have been developed that are safe and immunogenic: a quadrivalent vaccine (HPV4) targeting high-risk cervical cancer types 16 and 18, as well as the genital wart-associated types 6 and 11, and a bivalent (HPV2) vaccine targeting high-risk cervical cancer types 16 and 18.

Because most individuals acquire HPV soon after becoming sexually active, these vaccines are targeted at preadolescent or adolescent girls and boys before the onset of sexual activity. Recommendations regarding the use of HPV vaccines are summarized in Box 4.12 Quadrivalent HPV vaccine has recently been routinely recommended for males, for whom the vaccine provides direct benefits in preventing genital warts and anal cancer. Immunization of males is also expected to protect females through herd immunity.

Box 4. Recommendations for the Use of Human Papillomavirus (HPV) Vaccines
Girls 11 through 12 years of age should be immunized routinely with 3 doses of HPV4 or HPV2, administered at 0,1-2, and 6 months. The vaccines can be administered starting at 9 years of age at the discretion of the physician.
All girls and women 13-26 years of age who have not been immunized previously or have not completed the full vaccine series should complete the series.
Boys 11-12 years of age should be immunized routinely with 3 doses of HPV4 administered at 0,1-2, and 6 months. The vaccine can be administered starting at 9 years of age at the discretion of the physician.
Previous sexual activity is not a contraindication to HPV immunization or completion of the series.
HPV vaccines can be administered at the same visit as all other recommended vaccines.

HPV vaccine is contraindicated in individuals who have a history of severe hypersensitivity to yeast and in pregnant women. The vaccine should not be administered to individuals with moderate to severe febrile illness. The vaccine can cause syncopal episodes in adolescents after injection. Thus, vaccine recipients should sit of lie down for 15 minutes after administration.

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Summary

  • The adolescent years serve as a time that warrants special effort to administer routinely recommended vaccines not previously administered, such as hepatitis B, hepatitis A, varicella, and measles-mumps-rubella vaccines.
  • Given the increased incidence and case-fatality rate of meningococcal disease in the adolescent age group, adolescents should be routinely immunized with conjugate meningococcal vaccine.
  • Pertussis is common among adults and adolescents; these individuals serve as important reservoirs for infection and are often the index cases for younger infants and children.
  • Adolescents ages 11 to 18 years should be routinely vaccinated with acellular pertussis vaccine combined with tetanus and reduced diphtheria toxoid (Tdap).
  • All adolescents should be routinely immunized with human papillomavirus (HPV) vaccine at 11 to 12 years of age.

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Suggested Readings

  • Committee on Infectious Diseases. Meningococcal conjugate vaccines policy update: booster dose recommendations [published online ahead of print November 28, 2011]. Pediatrics 2011; 128:1213–1218. doi:10.1542/peds.2011-2380.
  • Centers for Disease Control and Prevention. Notice to readers: update recommendations of the Advisory Committee on Immunization Practices (ACIP) for the control and elimination of mumps. MMWR Morb Mortal Wkly Rep 2006; 55:629–630.
  • Bilukha OO, Rosenstein N; National Center for Infectious Diseases, Centers for Disease Control and Prevention (CDC). Prevention and control of meningococcal disease: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Morb Mortal Wkly Rep 2005; 54(RR-7):1–21.
  • Strebel P, Nordin J, Edwards K, et al. Population-based incidence of pertussis among adolescents and adults, Minnesota, 1995-1996 [published online ahead of print March 30, 2001]. J Infect Dis 2001; 183:1353–1359. doi:10.1086/319853.

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References

  1. Centers for Disease Control and Prevention. Measles–United States, 2011. MMWR Morb Mortal Wkly Rep 2012; 61:253–257.
  2. Zhou F, Harpaz R, Jumaan AO, Winston CA, Shefer A. Impact of varicella vaccination on health care utilization. JAMA 2005; 294:797–802.
  3. Lopez AS, Zhang J, Brown C, Bialek S. Varicella-related hospitalizations in the United States, 2000-2006: the 1-dose varicella vaccination era [published online ahead of print January 3, 2011]. Pediatrics 2011; 127:238–245. doi:10.1542/peds.2010-0962.
  4. Centers for Disease Control and Prevention. Updated recommendations for use of meningococcal conjugate vaccines–Advisory Committee on Immunization Practices (ACIP), 2010. MMWR Morb Mortal Wkly Rep 2011; 60:72–76.
  5. Bruce MG, Rosenstein NE, Capparella JM, Shutt KA, Perkins BA, Collins M. Risk factors for meningococcal disease in college students. JAMA 2001; 286:688–693.
  6. Broder KR, Cortese MM, Iskander JK, et al. Preventing tetanus, diphtheria, and pertussis among adolescents: use of tetanus toxoid, reduced diphtheria toxoid and acellular pertussis vaccines recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep 2006; 55(RR-3):1–34.
  7. Centers for Disease Control and Prevention. Pertussis–United States, 2001-2003. MMWR Morb Mortal Wkly Rep 2005; 54:1283–1286.
  8. Senzilet LD, Halperin SA, Spika JS, Alagaratnam M, Morris A, Smith B; Sentinel Health Unit Surveillance System Pertussis Working Group. Pertussis is a frequent cause of prolonged cough illness in adults and adolescents [published online ahead of print May 21, 2001]. Clin Infect Dis 2001; 32:1691–1697. doi:10.1086/320754.
  9. Ward JI, Cherry JD, Chang SJ, et al; APERT Study Group. Efficacy of an acellular pertussis vaccine among adolescents and adults. N Engl J Med 2005; 353:1555–1563.
  10. Centers of Disease Control and Prevention. Updated recommendations for use of tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap) vaccine from the Advisory Committee on Immunization Practices, 2010. MMWR Morbid Mortal Wkly Rep 2011; 60:13–15.
  11. Kulasingam SL, Hughes JP, Kiviat NB, et al. Evaluation of human papillomavirus testing in primary screening for cervical abnormalities: comparison of sensitivity, specificity, and frequency of referral. JAMA 2002; 288:1749–1757.
  12. Committee on Infectious Diseases. HPV vaccine recommendations [published online ahead of print February 27, 2012]. Pediatrics 2012; 129:602–605. doi:10.1542/peds.2011-3865.

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