Henry R. Shinefield

Efficacy, safety and immunogenicity of heptavalent pneumococcal conjugate vaccine in children.

Objective. To determine the efficacy, safety and immunogenicity of the heptavalent CRM197 pneumococcal conjugate vaccine against invasive disease caused by vaccine serotypes and to determine the effectiveness of this vaccine against clinical episodes of otitis media. Methods. The Wyeth Lederle Heptavalent CRM197 (PCV) was given to infants at 2, 4, 6 and 12 to 15 months of age in a double blind trial; 37 868 children were randomly assigned 1:1 to receive either the pneumococcal conjugate vaccine or meningococcus type C CRM197 conjugate. The primary study outcome was invasive disease caused by vaccine serotype. Other outcomes included overall impact on invasive disease regardless of serotype, effectiveness against clinical otitis media visits and episodes, impact against frequent and severe otitis media and ventilatory tube placement. In addition the serotype‐specific efficacy against otitis media was estimated in an analysis of spontaneously draining ears. Results. In the interim analysis in August, 1998, 17 of the 17 cases of invasive disease caused by vaccine serotype in fully vaccinated children and 5 of 5 of partially vaccinated cases occurred in the control group for a vaccine efficacy of 100%. Blinded case ascertainment was continued until April, 1999. As of that time 40 fully vaccinated cases of invasive disease caused by vaccine serotype had been identified, all but 1 in controls for an efficacy of 97.4% (95% confidence interval, 82.7 to 99.9%), and 52 cases, all but 3 in controls in the intent‐to‐treat analysis for an efficacy of 93.9% (95% confidence interval, 79.6 to 98.5%). There was no evidence of any increase of disease caused by nonvaccine serotypes. Efficacy for otitis media against visits, episodes, frequent otitis and ventilatory tube placement was 8.9, 7.0, 9.3 and 20.1% with P < 0.04 for all. In the analysis of spontaneously draining ears, serotype‐specific effectiveness was 66.7%. Conclusion. This heptavalent pneumococcal conjugate appears to be highly effective in preventing invasive disease in young children and to have a significant impact on otitis media.

Influenza and the Rates of Hospitalization for Respiratory Disease among Infants and Young Children

BACKGROUND Young children may be at increased risk for serious complications from influenzavirus infection. However, in population-based studies it has been difficult to separate the effects of influenzavirus from those of respiratory syncytial virus. Respiratory syncytial virus often circulates with influenzaviruses and is the most frequent cause of hospitalization for lower respiratory tract infections in infants and young children. We studied the rates of hospitalization for acute respiratory-disease among infants and children during periods when the circulation of influenzaviruses predominated over the circulation of respiratory syncytial virus. METHODS For each season from October to May during the period from 1992 to 1997, we used local viral surveillance data to define periods in Washington State and northern California when the circulation of influenzaviruses predominated over that of respiratory syncytial virus. We calculated the rates of hospitalization for acute respiratory disease, excess rates attributable to influenzavirus, and incidence-rate ratios for all infants and children younger than 18 years of age who were enrolled in either the Kaiser Permanente Medical Care Program of Northern California or the Group Health Cooperative of Puget Sound. RESULTS The rates of hospitalization for acute respiratory disease among children who did not have conditions that put them at high risk for complications of influenza (e.g., asthma, cardiovascular diseases, or premature birth) and who were younger than two years of age were 231 per 100,000 person-months at Northern California Kaiser sites (from 1993 to 1997) and 193 per 100,000 person-months at Group Health Cooperative sites (from 1992 to 1997). These rates were approximately 12 times as high as the rates among children without high-risk conditions who were 5 to 17 years of age (19 per 100,000 person-months at Northern California Kaiser sites and 16 per 100,000 person-months at Group Health Cooperative sites) and approached the rates among children with chronic health conditions who were 5 to 17 years of age (386 per 100,000 person-months and 216 per 100,000 person-months, respectively). CONCLUSIONS Infants and young children without chronic or serious medical conditions are at increased risk for hospitalization during influenza seasons. Routine influenza vaccination should be considered in these children.

Postlicensure surveillance for pneumococcal invasive disease after use of heptavalent pneumococcal conjugate vaccine in Northern California Kaiser Permanente.

Objective: To assess the direct and indirect effects of the introduction of routine use of pneumococcal conjugate vaccine in infants and toddlers at risk for invasive disease caused by vaccine serotypes and nonvaccine serotypes in vaccinated children and unvaccinated children of the same age. Secondary objectives included determination of the risk of pneumococcal infections in unvaccinated older children and adults in the same population and the impact of vaccine introduction on patterns of antimicrobial resistance. Methods: Northern California Kaiser Permanente provides integrated comprehensive care to 3.1 million people and has an annual birth cohort of 38,000 infants. Microbiology services use a regional laboratory. Automated laboratory results, immunization records as well as diagnoses for inpatient and outpatient utilization are available from clinical data bases. Beginning in April 2000, the heptavalent pneumococcal conjugate (PNCV7) vaccine was introduced into routine use in the Northern California Kaiser Permanente population. Cases of invasive pneumococcal disease were identified from the automated hospital diagnosis as well as laboratory databases for all individuals, vaccinees and nonvaccinees, inpatient and outpatient. For the purpose of these analyses, pneumococcal invasive disease was defined as a positive culture from a normally sterile site. Results: As of March 2003, 157,471 children had received 1 dose or more of PNCV7, but only 24% of those <2 years of age received all 4 doses as a result of shortages of vaccine. During the last year of observation, no cases of vaccine serotype disease were seen in children <1 year of age compared with an incidence ranging between 51.5 and 98.2 cases per 100,000 person-years (16–34 cases per year) in the years before vaccine introduction. Similar reductions were seen in children <5 years of age. There was no evidence of any concomitant increase in pneumococcal disease caused by nonvaccine serotypes. High level resistance of pneumococci to penicillin fell from a peak of 15% in 2000 to 5% in the first half of 2003. Similar trends were seen for other antibiotics. Conclusion: The PNCV7 vaccine is highly effective in reducing the burden of pneumococcal disease in children <5 years of age, and there is evidence of a herd effect as well as a decrease in the antibiotic resistant in strains causing disease. For invasive disease, there is no current evidence of serotype replacement.

Safety and immunogenicity of heptavalent pneumococcal CRM197 conjugate vaccine in infants and toddlers.

OBJECTIVES The objectives of this study were (1) to determine the safety and immunogenicity of heptavalent pneumococcal CRM197 conjugate (PNCRM7) vaccine in infants and (2) to determine the effect of concurrent hepatitis B immunization during the primary series and the effect of concurrent diphtheria and tetanus toxoid and acellular pertussis [DTaP (ACEL-IMUNE)] and conjugate CRM197 Haemophilus influenzae type b [HbOC (HibTITER) immunization at time of the booster dose on the safety and immunogenicity of PNCRM7and these other concurrently administered vaccines. METHODS This was a randomized double-blinded study in 302 healthy infants in the Northern California Kaiser Permanente (NCKP) Health Plan. Infants received either PNCRM7 vaccine or meningococcal group C conjugate vaccine as a control at 2, 4 and 6 months of age and a booster at 12 to 15 months of age. Study design permitted the evaluation of immunology and safety of concurrent administration of routine vaccines. Antibody titers were determined on blood samples drawn before and 1 month after the primary series and the booster dose. RESULTS After the third dose of PNCRM7 geometric mean concentrations (GMCs) ranged from 1.01 for serotype 9V to 3.72 microg/ml for serotype 14. More than 90% of all subjects had a post-third dose titer of > or =0.15 microg/ml for all serotypes, and the percentage of infants with a post-third dose titer of > or =1.0 microg/ml ranged from 51% for type 9V to 89% for type 14. After the PNCRM7 booster dose, the GMCs of all seven serotypes increased significantly over both post-Dose 3 and pre-Dose 4 antibody levels. In the primary series there were no significant differences in GMCs of pneumococcal antibodies between the subjects given PN-CRM7 alone or concurrently with hepatitis B vaccine. At the toddler dose concurrent administration of PNCRM7 and DTaP and HbOC resulted in a near conventional threshold for statistical significance of a post-Dose 4 GMC for serotype 23F [alone 6.75 mirog/ml vs. concurrent 4.11 microg/ml (P = 0.057)] as well as significantly lower antibody GMCs for H. influenza polyribosylribitol phosphate, diphtheria toxoid, pertussis toxin and filamentous hemagglutinin. For all antigens there were no differences between study groups in defined antibody titers that are considered protective. CONCLUSION We conclude that PNCRM7 vaccine was safe and immunogenic. When this vaccine was administered concurrently at the booster dose with DTaP and HbOC vaccines, lower antibody titers were noted for some of the antigens when compared with the antibody response when PNCRM7 was given separately. Because the GMCs of the booster responses were all generally high and all subjects achieved similar percentages above predefined antibody titers, these differences are probably not clinically significant.

Ten year follow-up of healthy children who received one or two injections of varicella vaccine.

Background. The rate of varicella and persistence of varicella antibody after a one dose vs. a two dose regimen of varicella virus vaccine live Oka/Merck (VARIVAX®; Merck & Co., Inc., West Point, PA) in ∼2000 children were compared during a 9- to 10-year follow-up period. Methods. Children 12 months to 12 years of age with a negative history of varicella were randomized in late 1991 to early 1993 to receive either one or two injections of varicella vaccine given 3 months apart. Subjects were actively followed for varicella, any varicella-like illness or zoster and any exposures to varicella or zoster on a yearly basis for 10 years after vaccination. Persistence of varicella antibody was measured yearly for 9 years. Results. Most cases of varicella reported in recipients of one or two injections of vaccine were mild. The risk of developing varicella >42 days postvaccination during the 10-year observation period was 3.3-fold lower (P < 0.001) in children who received two injections than in those who received one injection (2.2%vs. 7.3%, respectively). The estimated vaccine efficacy for the 10-year observation period was 94.4% for one injection and 98.3% for two injections (P < 0.001). Measurable serum antibody persisted for 9 years in all subjects. Conclusions. Administration of either one or two injections of varicella vaccine to healthy children results in long term protection against most varicella disease. The two dose regimen was significantly more effective than a single injection.

Postlicensure evaluation of the effectiveness of seven valent pneumococcal conjugate vaccine

Objective. To evaluate the impact of the introduction and routine use of seven valent pneumococcal conjugate vaccine on the epidemiology of invasive pneumococcal disease within the Northern California Kaiser Permanente (KP) population. Methods. Surveillance for invasive pneumococcal disease has been in place within KP since 1995. Isolates from normally sterile sites in children are routinely sent for serotyping. Cases of invasive disease are identified through review of automated microbiology records within KP. Incidence rates of invasive disease were compared for the period before and after routine use of pneumococcal conjugate vaccine in children. Results. The incidence of invasive pneumococcal disease caused by vaccine serotypes before the licensure and routine use of pneumococcal conjugate vaccine ranged between 51.52 and 98.15 cases per 100 000 person years in children <1 year of age and fell to 9.35 after introduction of vaccine. The incidence in children <2 years of age was 81.67 to 113.80 before introduction and 38.22 cases per 100 000 person years after introduction of the vaccine into the general population. These reductions in disease rates exceeded the average vaccine coverage substantially in each age group. No increase in disease incidence was observed for possibly cross-reacting serotypes or nonvaccine serotypes. Conclusion. The introduction and routine use of pneumococcal conjugate vaccine in our population have been associated with a substantial reduction in invasive disease incidence in children <5 years of age.

Effectiveness of heptavalent pneumococcal conjugate vaccine in children younger than 5 years of age for prevention of pneumonia: Updated analysis using World Health Organization standardized interpretation of chest radiographs

Background: A World Health Organization (WHO) working group in 2001 developed a method for standardizing interpretation of chest radiographs in children for epidemiologic purposes. We reevaluated radiographs from the Kaiser Permanente Pneumococcal Efficacy trial using this method. Methods: Seven-valent pneumococcal conjugate vaccine was evaluated in a randomized, controlled study including 37,868 infants. Effectiveness against pneumonia was previously evaluated using the original treating radiologist reading. There were 2841 sets of radiographs from this trial and all available radiographs were scanned and read blindly by 2 WHO crosstrained readers (A and B); discordance between the 2 primary readers was resolved through a consensus reading by an adjudicating panel of 2 radiologists. Results: Of the 2841 radiographs, 2446 were available for scanning and were reviewed using WHO-defined descriptive categories. Two hundred fifty of the 2446 radiographs were read as positive by both readers. An additional 129 were read as positive by reader A only and 142 by reader B only for a total of 521 radiographs that were read as positive by one or both of the reviewers. The concordance rate between the 2 reviewers was 250 of 521 (48%). Of the 271 discordant radiographs, 45 of 129 (34.9%) of reader A and 66 of 142 (46.5%) for reader B were finalized as positive by the adjudicating panel. Overall, 361 radiographs were finalized as positive (12.7%). With these 361 images as the standard, the sensitivity and specificity of reader A were 82% and 97%, respectively, and for reader B, 88% and 97%, respectively. Kappa between the 2 readers was 0.58. Of 25 control radiographs read as positive by both A and B, 80% were also read as positive by the panel and all 25 control negative radiographs were read as negative by the panel. Using original readings by point-of-care radiologists, efficacy against first episode of radiograph confirmed pneumonia was 17.7% (95% confidence interval [CI] = 4.8–28.9%) in intent-to-treat and 20.5% (95% CI = 4.4–34%) in per protocol. Using the WHO method, the efficacy against first episode of radiograph confirmed pneumonia adjusting for age, gender and year of vaccination of 25.5% (95% CI = 6.5–40.7%, P = 0.011) for intent-to-treat and 30.3% (95% CI = 10.7–45.7%, P = 0.0043) for per protocol. Conclusion: Using WHO criteria for reading of radiographs increased point estimates of vaccine efficacy presumably as a result of improved specificity.

Efficacy in infancy of oligosaccharide conjugate Haemophilus influenzae type b (HbOC) vaccine in a United States population of 61 080 children

The efficacy of the HbOC conjugate Haemophilus influenzae type b vaccine was evaluated in a study population of 61 080 infants in the Northern California Kaiser Permanente Medical Care Program. Between February, 1988, and June, 1990, the HbOC vaccine was given as part of a three-dose series at 2, 4 and 6 months of age to 20 800 infants. The study population included children with a well-care visit at a study center during the first 6 months of life. There were 25 cases of Haemophilus influenzae type b disease in the study population: 22 in unvaccinated children and 3 in children who received only one dose of HbOC vaccine. The efficacy of the full three-dose series was evaluated by several methods: a primary analysis comparing fully vaccinated children with unvaccinated children from 7 to 18 months of age; a stratified exact analysis adjusted for age and seasonality; and a case-control analysis which further adjusted for known risk factors. The efficacy of three doses of vaccine was 100% with the lower bound of the 95% confidence interval for the three analyses at 68, 71, and 64%, respectively. There were no cases of disease resulting from two doses of HbOC vaccine yielding an estimate of 100% efficacy (95% confidence interval, 47 to 100) for two doses of HbOC vaccine. However, for children who had received only one dose of HbOC vaccine, vaccine efficacy was estimated to be 26% and the possibility that one dose of HbOC vaccine had no efficacy could not be excluded. An intent-to-treat analysis and supplementary analyses of possible sources of bias supported the conclusion that immunization with HbOC vaccine was effective in preventing H. influenzae type b disease in infancy.

Population-based study of rotavirus vaccination and intussusception

Background. During the first year that the rhesus rotavirus tetravalent vaccine (RRV-TV) was licensed, the Vaccine Adverse Event Reporting System received several reports of intussusception after vaccination. To evaluate the risk of intussusception, we conducted a retrospective cohort study in ten managed care organizations. Methods. Cases of intussusception were identified by searching electronic databases for diagnoses of intussusception (ICD-9 Code 560.0) in infants 1 to 11 months of age and confirmed by medical chart review. Vaccination and enrollment data were obtained from administrative databases. Incidence rate ratios (RR) of intussusception were computed by dividing incidence rates in prespecified risk intervals after vaccination by the background rate of intussusception and adjusted for age by Poisson regression. Cox proportional hazard regression was used to evaluate risk by vaccine dose. Results. Of 463 277 children 56 253 had been vaccinated with a total of 91 371 doses of RRV-TV. The incidence rate of intussusception was 25/100 000 person years among unexposed infants and 340/100 000 person years 3 to 7 days postvaccination. In the interval 3 to 7 days after vaccination, the age-adjusted RR was 16.0 (95% confidence interval, 5.5 to 46.7) for all doses combined and 30.4 (95% confidence interval, 8.8 to 104.9) after the first dose. RRs for the 8- to 14- and 15- to 21-day risk intervals were >1.0, but the confidence intervals substantially overlapped 1.0. The attributable risk was one case of intussusception per 11 073 children vaccinated. Conclusions. RRV-TV is associated with an increased risk of intussusception. The risk is greatest 3 to 7 days after the first vaccination dose.

The Vaccine Safety Datalink: immunization research in health maintenance organizations in the USA

The Vaccine Safety Datalink is a collaborative project involving the National Immunization Program of the Centers for Disease Control and Prevention and several large health maintenance organizations in the USA. The project began in 1990 with the primary purpose of rigorously evaluating concerns about the safety of vaccines. Computerized data on vaccination, medical outcome (e.g. outpatient visits, emergency room visits, hospitalizations, and deaths) and covariates (e.g. birth certificates, census data) are prospectively collected and linked under joint protocol at multiple health maintenance organizations for analysis. Approximately 6 million persons (2% of the population of the USA) are now members of health maintenance organizations participating in the Vaccine Safety Datalink, which has proved to be a valuable resource providing important information on a number of vaccine safety issues. The databases and infrastructure created for the Vaccine Safety Datalink have also provided opportunities to address vaccination coverage, cost-effectiveness and other matters connected with immunization as well as matters outside this field.