Advisory committee on immunization practices




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Opposed: None

Abstained: Treanor (conflict).


The vote passed.


V.F.C. Resolution Vote

Presenter: Dr. Greg Wallace


A.C.I.P. approval of a V.F.C. resolution establishes the vaccine’s eligibility to be administered for free to children in the V.F.C. program. V.F.C. eligibility is conferred to those aged less than 18 years and eligible for Medicaid, those without health insurance, Native Americans or Alaska Natives, or those underinsured for vaccines who are vaccinated in a federally qualified health center or a rural health clinic.


This V.F.C. resolution for hepatitis A was to revise the previous resolution to incorporate this new universal vaccine recommendation, and to extend that recommendation down to age one year. It specifies all persons aged 1 to 18 years as eligible through the V.F.C. program. Of the vaccines, Twinrix® is licensed only for those aged ≥18 years and is given in three doses at intervals of 0, 1, and 6 months. The Havrix® and Vaqta® schedules have a two dose series, with the second dose at 6 to 12 or 6 to 18 months, respectively, after the first. An asterisk addresses the catch-up as discussed, and enhancing existing programs to reach one-year-olds, but not replacing existing programs. Finally, the text on high-risk groups was deleted, since this is now a universal recommendation.


Dr. Lieu moved to approve the V.F.C. resolution and Dr. Morita seconded the motion.


Vote

In favor: Allos, Beck, Campbell, Finger, Gilsdorf, Hull, Lieu, Marcuse, Morita, Womeodu, Abramson

Opposed: None

Abstained: Treanor (conflict).


The vote passed.


PERTUSSIS


A.C.I.P. Pertussis Vaccine (Tdap) Working Group

Presenter: Dr. Morita, for Dr. Dale Morse, Pertussis Working Group Chair


Overview: Working Group activities, June 2005 adolescent recommendation, proposed recommendation for adult Tdap vaccination


Since June of 2004, the multi-representational Pertussis Working Group held more than 30 meetings and teleconferences and was invited to participate in an international pertussis panel. The Working Group presented information to the A.C.I.P. in February and June 2005. At the June A.C.I.P. meeting, the A.C.I.P. recommended a single dose of Tdap routinely at age 11 to 12 years, and for all adolescents aged 11 to 18 years if they have not received Td. The A.C.I.P. recommended that adolescents who received Td but not Tdap receive a single dose of Tdap for pertussis protection, taking into account the interval from the last dose of tetanus and diphtheria toxoid-containing vaccine.


In this meeting, the A.C.I.P. will be asked to consider recommendations for one of the two U.S. Tdap products licensed for single-dose use among adults through age 64 years. The primary objective for a Tdap program for adults is to protect vaccinated adults from pertussis. Secondary objectives include vaccinating adults to: decrease exposures of persons at increased risk of severe pertussis and its complications (for example, infants aged less than 6 months), to reduce the costs and disruption of pertussis outbreaks in institutional settings, and to reduce the overall reservoir of Bordetella pertussis.


Several assumptions underlie presentations today. Tdap is licensed for use as a single dose among adults less than 65 years of age. Immunity to pertussis wanes at 5 to 10 years after either vaccine or infection. Booster doses will be required about every ten years to maintain protection. Uptake of decennial Td booster by adults is suboptimal and will require education to improve protection against pertussis via Tdap (1999 N.H.I.S. found approximately 55 to 67 percent Td vaccinated adults). Tdap price is approximately 20 dollars more than Td. No acellular pertussis vaccine without tetanus and diphtheria toxoids is available; this decreases flexibility for adding protecting against pertussis.


The Working Group reached strong consensus in support of replacing Tdap for Td in adults, proposing:

  • A general recommendation for adult Tdap to replace one dose of decennial Td. This proposal was based on recognition that most susceptible adults are not in an identified risk group, yet still have substantial morbidity with pertussis.

  • A targeted recommendation for adults who have or will have contact with infants aged less than 6 months.

  • Consideration for administering Tdap at shortened intervals after Td in situations when the perceived risk of pertussis or the benefits of vaccine are high.


A discussion of Tdap for healthcare workers and adults aged greater than 65 years will be deferred to a subsequent A.C.I.P. meeting.


Efficacy/Safety of Tdap Use among Adults

Presenter: Dr. Karen Broder, N.I.P.


Overview: Review of immunogenicity and safety data from U.S. Tdap (ADACEL™) pre-licensure trials in adults and a Canadian post-licensure safety study of intervals less than 5 years between Td and Tdap.


Two Tdap (Tetanus Toxoid, Reduced Diphtheria Toxoid and Acellular Pertussis Vaccines, Adsorbed) vaccines were F.D.A.-licensed in 2005 for use among adolescents and adults. GlaxoSmithKline Biologicals’, BOOSTRIX® is indicated for use among adolescents aged 10 to 18 years, and sanofi pasteur’s ADACEL™ is indicated for adolescents and adults aged 11 to 64 years. Tdap is indicated as a single-dose booster to prevent tetanus, diphtheria, and pertussis; neither Tdap vaccine is licensed for use in more than one dose.


sanofi pasteur’s Tdap for use among adults aged 18 to 64 years contains lower levels of diphtheria toxoid and inactivated pertussis toxin than sanofi pasteur’s DAPTACEL® (D.T.a.P.) product, formulated for use in infants and children. The Tdap and Td vaccines manufactured by sanofi pasteur have the same quantities of tetanus and diphtheria toxoids.


Efficacy. Tdap licensure was based on comparative immunogenicity and safety studies, and the protective efficacy of the antigens in Tdap was inferred from the immunogenicity data. The seroprotective and booster response rates in adults one month after Tdap vaccination were non-inferior to Td, the standard of care. In contrast to tetanus and diphtheria, there are no well acceptable serological correlates of protection against pertussis. The geometric mean antibody concentrations (G.M.C.s) for pertussis antigens in adults vaccinated with one dose of Tdapsp were non-inferior to the G.M.C.s in Swedish infants vaccinated with 3 doses of DAPTACEL® D.T.a.P. In the Sweden I vaccine efficacy (V.E.) trial, the V.E. of 3 doses of DAPTACEL® against W.H.O.-defined pertussis was 85 percent (80 percent to 89 percent). Booster responses to pertussis antigens in adults vaccinated with Tdapsp were acceptable based on pre-defined criteria

Safety. Adverse reaction rates were compared between Tdap and Td recipients. Rates of pain, erythema and swelling were similar in the two groups demonstrating non-inferiority. No case of whole-arm swelling was reported. Adults reported pain at a lower rate than adolescents studied in a separate Tdap study. Rates of fever and other systemic reactions were comparable after Tdap and Td, as were rates of serious adverse events assessed at six-months after the adult primary safety study. After four U.S. ADACEL® pre-licensure safety studies (N equal 6000 subjects), two serious adverse events in adults were assessed by the study investigators as possibly related to Tdap. Both occurred in women and both resolved without sequelae.


Canadian trials. A Canadian study examined short interval between tetanus and diphtheria toxoid-containing vaccinations for rates of local and systemic adverse reactions, including Arthus. Use of tetanus and diphtheria toxoid-containing vaccines at short, frequent intervals historically was associated with unacceptable rates of local and systemic adverse vaccination reactions, including Arthus. The A.C.I.P. currently routinely recommends Td boosters in adults every 10 years. Td is recommended at a 5 year interval after the last Td in wound management.


A decennial Td booster schedule provides adequate protection against tetanus and diphtheria. Administration of Tdap at intervals shorter than 5 years after Td to protect against pertussis might be desirable. Halperin et al (PIDJ, in press, 2006) studied Tdap at intervals less than 5 years after Td or the last childhood D.T.P./D.T.a.P. in Canada using ADACEL™ (same vaccine licensed in the United States) . Outcomes among approximately 6000 Prince Edward Island children and adolescents aged 7 to 19 years were assessed. Rates of selected adverse events after Tdap were compared between subjects vaccinated at 2 to 9 years since the last tetanus- and diphtheria-containing vaccine versus a reference cohort who received a tetanus and diphtheria-toxoid containing vaccine ≥10 years earlier. The 2-year interval cohort included 464 subjects who were vaccinated with tetanus and diphtheria toxoid-containing vaccine18 to 30 months before Tdap.


Results: No vaccine-related serious adverse event or Arthus was reported. Rates of pain and fever were comparable in all cohorts. Higher rates of “any erythema” and swelling, but not “severe erythema” and swelling were found in the 4 to 7 year interval cohorts, but were not observed in other cohorts, including the two-year interval cohort. The 4 to 7-year interval cohorts received one or two doses of acellular D.T.a.P. vaccine during childhood, whereas the other cohorts received only whole-cell D.T.P. vaccine during childhood. This finding suggested that rates of reactions after Tdap might be higher among subjects who receive acellular D.T.a.P. compared with subjects who receive only whole-cell D.T.P. vaccine.

No safety study of short intervals among adults was done. In the ADACEL pre-licensure trials, rates of local and systemic reactions following administration of Tdap in adults were lower than or comparable to rates in adolescents. The safety of using intervals as short as approximately 2 years between Td and Tdap in adults can be inferred from data in the Canadian study of children and adolescents


In summary, a single dose of Tdap ADACEL® is safe and immunogenic in adults aged 19 to 64 years. Repeat doses of Tdap have not been studied. The safety of intervals as short as approximately two years between Td or childhood D.T.P./D.T.a.P. and Tdap is supported by a Canadian post-licensure study.


Post-licensure Safety of Tdap and Td in Adults

Presenter: Dr. John Iskander, Immunization Safety Office (I.S.O.)


Overview: Early post-marketing V.A.E.R.S. Tdap safety data and other post-licensure safety data; neurological adverse events possibly (but rarely) associated with tetanus- or pertussis-containing vaccines.


V.A.E.R.S. is a national passive surveillance system for licensed vaccines; its data must be carefully interpreted as the system is limited by underreporting and reporting of unconfirmed diagnoses. To date, V.A.E.R.S. has received 39 reports for licensed Tdap products. Most events occurred in adolescents who received Tdap alone or in combination with meningococcal conjugate vaccine. Most of the symptoms reported were local and mild systemic reactions. Adverse events reported included:

  • One sudden cardiac death from cardiac arrhythmia, two weeks after vaccination.

  • Five reports of seizure occurring after vaccination with Tdap; all recovered.

  • No Tdap reports of Guillain-Barré Syndrome, brachial neuritis, transverse myelitis, or Bell’s Palsy.

  • Two cases of seizure judged to be vaccine-related in persons with numerous other possible causes of seizure in their medical histories, or with concurrent illness.

  • One pregnancy exposure. Pregnancy is not a contraindication in the preliminary A.C.I.P. recommendations for Tdap in adolescents.

  • Vaccine administration errors; none resulted in significant adverse reactions. Tdap and a pediatric D.T.a.P. formulations are similarly packaged.

  • Two reports of injection-site reactions fit a general description of extensive limb swelling (E.L.S.); both patients recovered. E.L.S. was previously documented following D.T.a.P., M.C.V.4, and several other pediatric and adult vaccines.

  • Serious Td-related local reactions appear to be rare; some literature suggests that the local reaction profile for Tdap could resemble that of Td.

References:

1. Macko MB, Powell CE. Ann Emerg Med 1985;14:33-5

2. Zurrer G, Steffen R. In: Proceedings of the Conference on International Travel Medicine, Zurich, Switzerland, 1988

3. Lloyd JC, Haber P, Mootrey GT et al. Vaccine. 2003 Sep 8;21(25-26):3746-50.

4. Southern J, Andrews N, Burrage M et al. Vaccine. 2005 May 31;23(29):3829-35. Epub 2005 Mar 30.


Neurologic events. Two 1994 I.O.M. reports found a rare causal relationship between tetanus toxoid containing vaccines and Guillain-Barré Syndrome and brachial neuritis, both based on uncontrolled data. Post-licensure Tdap data from both V.A.E.R.S. and published sources support a similar safety profile to that of Td. While rare serious neurological adverse events warrant continued surveillance, none has been associated with Tdap in post-licensure safety reports. The current recommendations were outlined for the administration or deferral of pertussis vaccines in children with seizure disorders or certain other neurological conditions. (source: A.C.I.P. recommendations published in M.M.W.R. in 1997, 2002)


Pertussis in Adults

Presenter: Dr. Margaret Cortese, N.I.P.


Overview: Clinical pertussis disease data supporting the case for prevention.


The licensure and uptake of pertussis vaccine were associated with reduction in reported U.S. cases by 99 percent, from approximately 270,000 cases and greater than 10,000 deaths in the mid-1930s to approximately less than 2000 cases in 1976. However, pertussis remains endemic in the US, and reported cases peak every 3 to 4 years. Reported annual number of cases rose to almost 26,000 in 2004, and 28 percent of the reported cases were in adults. The clinical spectrum of pertussis in adults ranges widely from mild cough illness (which is contagious), to classic pertussis. Asymptomatic infection also occurs. The clinical outcome of pertussis is determined in part by the degree of immunity. Immunity depends on the time since the last exposure to vaccine or to B. pertussis. Vaccination before exposure is the best prevention; the effectiveness of post-exposure antibiotic prophylaxis is limited as a public-health response.


Morbidity. These data are charted from 1996 to 2004 U.S. passive surveillance reports of pertussis among adults aged 19 to 64 years (the adult age group for whom Tdap is currently licensed), and aged ≥ 65 years. Also charted are Massachusetts surveillance reports of pertussis among adults aged ≥18 years. The clinical features of the U.S. and Massachusetts groups are very similar. Adult pertussis illness features were:

  • Paroxysmal cough: 77 percent of adults, 40 to 50 percent with vomiting (less in older adults).

  • Coughing spells causing urinary incontinence: 28 percent, Massachusetts; 33 percent, Quebec, among women aged ≥50 years.

  • Cough syncope (unconsciousness): 6 percent, Massachusetts, 3 percent, Quebec; 0 percent, Sweden, Australia.

  • Rib fractures: 4 percent, Massachusetts; 4 percent, Quebec, all among women; 1 percent, Sweden. It is possible that persons with severe cardiac or pulmonary disease, or the very elderly, could suffer greater adverse outcomes from severe coughing spells.

  • Other features: difficulty breathing, sleeping: 86 percent; weight loss: 33 percent; seizures: 1 percent; X-ray-confirmed pneumonia: 2 to 5 percent, possibly higher in older adults; hospitalization: 2 to 3 percent (10 percent in older adults).

  • Cough in pertussis is prolonged: commonly three weeks, median in adults 2 to 3 months, range 2 weeks to 8 months. Patients usually cough (and spread infection) for weeks before they're diagnosed; 50 percent of Massachusetts adults had been coughing for ≥1 month before diagnosis, at which point treatment does not lessen symptoms.

  • Number of visits for medical care visits was 0 to 12, with a median of two visit in a Massachusetts study; from Massachusetts surveillance data, 33 percent patients required ≥3 medical visits. Extensive testing may be undertaken by providers if pertussis is not suspected.

  • Work lost, mean of 10 days, in 61 percent of cases among employed Massachusetts adults; range was1 to 180 days; data from foreign studies are similar.

  • Other rare complications (anecdotally reported) include pneumo-thorax, pneumo-mediastinum, carotid dissection, herniated lumbar disc, inguinal hernia, pertussis encephalopathy.


Mortality. Deaths among adults from pertussis are rare, although likely underreported. Five were reported since 1997; each occurred in an adult with significant underlying medical condition. One reported outbreak in the Netherlands among elderly women in a religious institution occurred in 1992. The attack rate was 53 percent; 3 deaths were reported from acute intracranial hemorrhage during pertussis cough illnesses of greater than 100 days.


The burden of pertussis in US adults is clearly underestimated by passive surveillance data, in part because of the limited availability of accurate diagnostics, limited physician awareness of pertussis in adults, and the difficulty in clinically distinguishing non-classic pertussis from other respiratory illnesses in adults.


U.S. Data. Prospective studies are needed to estimate the true burden of pertussis in adults; these are challenging because of the limitations of laboratory test confirmation and by ascertaining the target population for surveillance. However, some studies provide useful information. Pertussis incidence studies by Strebel (1995 to 1996), Ward (1997 to 2001), Nennig (1994 to 1995) and Mink (1986 to 1989) are outlined here. Diagnoses were made using from culture, PCR and/or anti-pertussis toxin serology results (and other serological assays in one study). For comparison, the 2004 pertussis cases reported to the N.N.D.S.S. among adults in this age group was approximately 6,700, or 4 per 100,000, demonstrating the great underestimation of passive surveillance.


The Strebel et al study reported an incidence of 361 per 100,000 person-years, and Ward et al study estimated 370 per 100,000 person-years. These extrapolate to annual case estimates of 600,000 and 615,000 (applying the study incidence rates to the 2000 U.S. census population for persons aged 20 to 64 years), respectively. Nennig et al found an incidence of 176 per 100,000 person-years, or 300,000 cases per year (by extrapolation). Mink et al focused on college students and estimated incidence at 35 and 69 per 100,000 (depending on the laboratory diagnostic criteria used) for annual adult case estimates of 58,000 and 115,000, if these rates were applied to the adult age group. The studies’ range of results is due in part to the age group studied, the type of confirmatory laboratory tests used, the source of the study population (for example, HMO outpatient visit, prospective vaccine trial, etc).


These studies, and 3 other US studies estimate the proportion of cough illness in adults attributable to pertussis. The studies differ somewhat in methodology. Using the most stringent laboratory requirements, 1 percent to 12 percent of all cough illness was laboratory confirmed as pertussis. The three other studies produced similar ranges, from 1 percent to 16 percent. Higher proportions of pertussis among cough illness were obtained with less pertussis-specific serologic assays (up to 17 to 26 percent).


An analysis of NHANES III 1991 to 1994 data by Baughman et al determined the proportion of the population with elevated I.g.G anti-pertussis toxin, to estimate the prevalence of recent pertussis infection in US adolescents and adults. Their estimate among U.S. adults aged 20 to 49 years was 2,700 per 100,000 population; these estimates support the concept that pertussis is endemic among U.S. adults. In a 2004 statewide outbreak of pertussis in Wisconsin, active early case detection, treatment and prophylaxis identified 5070 PCR-confirmed cases, including 111 hospitalized cases, half among infants aged less than 6 months, at highest risk of severe disease. Of the 1660 cases in adults aged 20 to 64 years (again, passive surveillance data, incidence of 50 per 100,000), 53 had pneumonia, 25 were hospitalized, and one elderly man with C.O.P.D. died.

Adults as source of pertussis for young infants will now be reviewed. Charted data from 1984 to 2004 show the highest incidence of pertussis (greater than or equal to 200 per 100,000) is among the youngest infants (aged 0 to 2 months), who are at highest risk for severe disease, and have the highest mortality rates of older infants and young children. Most of the deaths occurred before the infant could have received the second or third protective dose of pertussis-containing vaccine. During 2000 to 2004, more infants died of pertussis than in all of the 1990s; of these, 92 percent were aged less than 6 months. Again, these data are under-reports. Vitek et al (Pediatr Infect Disease J 2003,22:828-34) determined approximately 65 percent case report to C.D.C. completeness of diagnosed cases from 1990 to 1999. Studies abroad also indicate pertussis deaths in infants are under-reported.


Bisgard et al (Pediatr Infect Disease J
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