Paralytic syndromes in children: epidemiology and relationship to vaccination

Acute flaccid paralysis is a standard outcome for detection of poliomyelitis globally and an ongoing potential vaccine-associated adverse event concern for polio, influenza, and meningococcal vaccines. No systematic population-based data on the epidemiologic and clinical features of this condition, or its potential association with immunization, have been reported from the United States. The present retrospective cohort study of acute flaccid paralysis in the Southern and Northern California Kaiser Permanente Health Care Plans was conducted using computerized diagnosis data and medical record review of potential cases among children aged 1 month to <15 years and diagnosed from January 1, 1992 through December 31, 1998. In all, 3297 potential cases were identified; of these, 2682 cases (81%) did not meet the case definition, and of the remaining 615 cases, 245 (7% of the total) were included. The incidence of disease was 1.4 per 100,000 children/year (95% confidence interval = 1.2-1.6); predicting approximately 844 children/year in the United States. Disease incidence did not vary with season or sex, varied inversely with age, and declined 28% during the study period. No cases of vaccine-associated acute flaccid paralysis were identified. In nonendemic countries, ongoing acute flaccid paralysis surveillance is often conducted, because of the risk of poliovirus importation, but this practice may be difficult to justify, given low disease incidence and breadth of clinical presentation.

Evaluation of vaccine coverage for low birth weight infants during the first year of life in a large managed care population

OBJECTIVE

There are few recent population-based assessments of vaccine coverage in premature infants available. This study assesses and compares age- and dose-specific immunization coverage in children of different birth weight categories during the first year of life.

METHODS

We performed a retrospective cohort analysis of computerized vaccination data from a large managed care organization in southern California. The participants were children born between January 1, 1997, and December 31, 2002, and continuously enrolled from birth to at least 12 months of age in the Southern California Kaiser Permanente health plan. We measured age-specific up-to-date and age-appropriate immunization rates according to birth weight (extremely low birth weight: <1000 g; very low birth weight: 1000-1499 g; low birth weight: 1500-2499 g; normal birth weight: >/=2500 g) for 4 vaccines (hepatitis B, diphtheria and tetanus toxoids with pertussis, Haemophilus influenzae type b, and poliovirus) through the first year of life.

RESULTS

We identified 127 833 infants born during the study period and continuously enrolled through the first year of life; 120 048 were normal birth weight infants; 6491 were low birth weight infants; 788 were very low birth weight infants; and 506 were extremely low birth weight infants. Vaccine-specific age-appropriate immunization rates were 3% to 15% lower for low birth weight infants and 17% to 33% lower for extremely low birth weight infants compared with the rates for normal birth weight infants in the first 6 months of life. Extremely low birth weight infants had the lowest age-specific up-to-date immunization levels (5%-31% lower) compared with normal birth weight infants at each age assessed. By 12 months, extremely low birth weight infants still had significantly lower up-to-date levels (87%) compared with very low birth weight, low birth weight, and normal birth weight infants (91%-92%).

CONCLUSIONS

Despite recommendations that lower birth weight infants be vaccinated as the same chronological age as normal birth weight infants, extremely low birth weight and very low birth weight infants are immunized at significantly lower rates relative to low birth weight and normal birth weight infants at 2, 4, and 6 months of age. However, by 12 months of age this finding persists only in extremely low birth weight infants.

A population-based, postlicensure evaluation of the safety of a combination diphtheria, tetanus, acellular pertussis, hepatitis B, and inactivated poliovirus vaccine in a large managed care organization

BACKGROUND

Prelicensure studies of diphtheria, tetanus, acellular pertussis, hepatitis B, inactivated polio virus vaccine suggested that there were higher rates of fever after its administration than when its component antigens were given separately.

METHODS

We conducted an open, controlled, cohort study to evaluate selected potential adverse events after receipt of diphtheria, tetanus, acellular pertussis, hepatitis B, inactivated poliovirus vaccine in the Southern California Kaiser Permanente Health Care Plan. From April 2003 through June 2005, we identified 61,004 infants who received >or=1 dose of vaccine (120000 total doses). This group was compared with a previous cohort of 58,251 age-, gender-, and medical center-matched infants (116,637 doses) who received diphtheria, tetanus, acellular pertussis vaccine and separate doses of hepatitis B and inactivated poliovirus vaccines from January 2002 through March 2003. We compared the incidence of seizures, medically attended events that were associated with fever, and other selected adverse outcomes.

RESULTS

We identified 16 infants (8 with fever) who had a seizure in the diphtheria, tetanus, acellular pertussis, hepatitis B, inactivated poliovirus cohort and 15 infants (6 with fever) among control subjects in the 8-day period after receipt of any dose of vaccine. The incidence of all seizures or seizures associated with fever was not significantly different between cohorts. The incidence of medically attended events that were associated with fever in the 4-day period after any dose of vaccine was also similar in both cohorts. As well, no significant differences between the diphtheria, tetanus, acellular pertussis, hepatitis B, inactivated poliovirus and control cohorts, were noted in the incidence of allergic reactions within 48 hours of any dose of vaccine, outpatient visits within 21 days, hospitalizations within 21 days, or death within 1 year.

CONCLUSIONS

We did not observe a statistically significant increase in any of several clinically important safety events after diphtheria, tetanus, acellular pertussis, hepatitis B, inactivated poliovirus vaccination compared with a historical cohort who received separate component vaccines.

Incidence of bacterial meningitis in Asia using enhanced CSF testing: polymerase chain reaction, latex agglutination and culture

To enhance the detection of bacterial meningitis in an East Asian surveillance study, we employed cerebrospinal fluid (CSF) bacterial culture, latex agglutination (LA) and polymerase chain reaction-enzyme immunoassay (PCR-EIA) testing for Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae (Sp). The sensitivity and specificity of CSF PCR-EIA testing was compared to LA and culture. A meningitis case was defined by one positive result for any of the three tests. The sensitivity of H. influenzae CSF PCR-EIA, LA, and culture was 100%, 40% and 57.5% respectively; and for Sp CSF PCR-EIA, LA and culture, the sensitivity was 100%, 58.3% and 66.7%, respectively. Hib and Sp specificity was 100% by each method. CSF PCR-EIA was more sensitive than culture or LA for the detection of Hib and Sp meningitis cases increasing their incidence by 74% and 50% compared to culture respectively. CSF PCR-EIA should be included for the detection of bacterial meningitis in surveillance studies.

Bordetella Pertussis infections in vaccinated and unvaccinated adolescents and adults, as assessed in a national prospective randomized Acellular Pertussis Vaccine Trial (APERT)

BACKGROUND

Acellular pertussis (aP) booster immunizations have been recommended for adolescents and older persons to enhance long-term protection and to possibly reduce community transmission of infections.

METHODS

This was a multicenter, randomized, double-blind vaccine trial in which one-half of the subjects received aP vaccine and one-half received hepatitis A vaccine (control subjects). All subjects were observed for almost 2 years for cough illnesses, and all underwent microbiologic and serologic studies for detection of pertussis infection. Immunoglobulin G (IgG) and immunoglobulin A (IgA) antibodies to pertussis toxin, filamentous hemagglutinin, pertactin, and fimbriae 2/3 were measured by enzyme-linked immunosorbent assay in serum samples obtained 1 and 12 months after immunization. Infection rates were determined with a variety of serologic criteria for control and vaccinated subjects. The incidence of prolonged cough illness was ascertained for subjects with and subjects without serologic evidence of infection.

RESULTS

Infection rates among control subjects are particularly representative of those in nonimmunized adults. Among control subjects, 0.4%-2.7% had increases in pertussis antibody of various types and degrees over 1 year, and 20%-46% had prolonged cough illnesses during this interval. Pertussis toxin antibody had the greatest specificity for detecting increases in antibody levels. Asymptomatic infections were approximately 5 times more common than clinical illnesses that met a strict clinical and microbiologic case definition. Relative to control subjects, aP-immunized subjects may have fewer increases in the antibody level (i.e., infections), especially for antibodies to fimbriae 2/3 (an antigen not in the vaccine).

CONCLUSIONS

Pertussis infections in older persons are largely asymptomatic. aP boosters confer protection for adolescents and adults against symptomatic pertussis and likely confer protection against mild and asymptomatic infections, and use of boosters may reduce transmission to others, especially infants.

Haemophilus influenzae type B meningitis among children in Hanoi, Vietnam: epidemiologic patterns and estimates of H. Influenzae type B disease burden

From March 2000 to February 2002, a population-based study of Haemophilus influenzae type b (Hib) meningitis was conducted among children less than five years of age in Hanoi, Vietnam. Children with suspected bacterial meningitis were referred to hospitals and each patient underwent standardized clinical examination and microbiologic testing. In Hanoi, 580 children were evaluated for bacterial meningitis and 23 (4%) had confirmed or probable Hib meningitis. The incidence of all Hib meningitis was 12/100,000 child-years less than five years of age and 26/100,000 child-years less than two years of age. Nationally, an estimated 1,005 children less than five years of age are hospitalized for Hib meningitis and 5,107 are hospitalized for Hib pneumonia. Among children with Hib meningitis, at least 100 will develop severe neurologic sequelae and 40 will die. These data suggest there is a substantial burden of Hib disease in Vietnam. National leaders will be provided with these data to facilitate development of national vaccination policies for children in Vietnam.

Efficacy of an acellular pertussis vaccine among adolescents and adults

BACKGROUND

Pertussis immunization of adults may be necessary to improve the control of a rising burden of disease and infection. This trial of an acellular pertussis vaccine among adolescents and adults evaluated the incidence of pertussis, vaccine safety, immunogenicity, and protective efficacy.

METHODS

Bordetella pertussis infections and illnesses were prospectively assessed in 2781 healthy subjects between the ages of 15 and 65 years who were enrolled in a national multicenter, randomized, double-blind trial of an acellular pertussis vaccine. Subjects received either a dose of a tricomponent acellular pertussis vaccine or a hepatitis A vaccine (control) and were monitored for 2.5 years for illnesses with cough that lasted for more than 5 days. Each illness was evaluated with use of a nasopharyngeal aspirate for culture and polymerase-chain-reaction assay, and serum samples from patients in both acute and convalescent stages of illness were analyzed for changes in antibodies to nine B. pertussis antigens.

RESULTS

Of the 2781 subjects, 1391 received the acellular pertussis vaccine and 1390 received the control vaccine. The groups had similar ages and demographic characteristics, and the median duration of follow-up was 22 months. The acellular pertussis vaccine was safe and immunogenic. There were 2672 prolonged illnesses with cough, but the incidence of this nonspecific outcome did not vary between the groups, even when stratified according to age, season, and duration of cough. On the basis of the primary pertussis case definition, vaccine protection was 92 percent (95 percent confidence interval, 32 to 99 percent). Among unimmunized controls with illness, 0.7 percent to 5.7 percent had B. pertussis infection, and the percentage increased with the duration of cough. On the basis of other case definitions, the incidence of pertussis in the controls ranged from 370 to 450 cases per 100,000 person-years.

CONCLUSIONS

The acellular pertussis vaccine was protective among adolescents and adults, and its routine use might reduce the overall disease burden and transmission to children.

Economic considerations for pertussis booster vaccination in adolescents

BACKGROUND

Despite good acellular pertussis vaccine safety and protective efficacy, as well as high vaccination rates among young children, the incidence of pertussis in the United States has steadily increased since the 1980s. This is especially true for adolescents and adults who are susceptible because of waning immunity, which is not long lived. Other populations are at increased risk for morbidity of infection, although infants younger than 6 months of age who have not completed the primary immunization series have the greatest morbidity and mortality. Other groups who might benefit from booster immunizations include hospital workers, family contacts, and individuals with compromised health. Although older individuals generally have milder illnesses, they are often the source of infection for younger children. An adolescent/adult formulation of acellular pertussis vaccine requires a lower dose of pertussis antigens and can be combined with currently recommended diphtheria and tetanus toxoids (Tdap). These new vaccines for adolescents and adults are safe, immunogenic, and protective.

METHODS

Through an extensive review of the literature, the direct and indirect costs associated with pertussis and its complications are examined, cost-benefit analyses of pertussis booster vaccination are evaluated for different groups, and the economic considerations involved in implementing a pertussis booster vaccination program in adolescents are discussed.

RESULTS

Pertussis infections cause outbreaks in schools, families, and workplaces, resulting in prolonged morbidity and significant costs for medical care, lost time, and wages. Physician visits, chest radiographs, and antibiotics comprise the majority of direct costs, and costs associated with work loss often comprise the majority of indirect costs related to pertussis illness. Adolescents and adults also transmit their infections to nonimmune children. A cost-benefit analysis evaluated the health and economic benefits of seven strategies for administering a pertussis booster. The most economical strategy is to immunize all adolescents 10-19 years of age, which may prevent 0.4-1.8 million cases of pertussis and save US 0.3-1.6 billion dollars in a decade. A tetanus and diphtheria booster (Td) is currently recommended for children 11-12 years of age. The Tdap vaccine offers an enhancement for the Td booster by providing protection against pertussis, and it will not require an additional injection or office visit.

CONCLUSIONS

Immunizing adolescents with a pertussis booster in the form of Tdap is the most economical and easiest-to-implement strategy and should provide significant health and economic benefits.

A bovine parainfluenza virus type 3 vaccine is safe and immunogenic in early infancy

BACKGROUND

A phase 2 trial was conducted to assess in young infants the safety, tolerability, infectivity, and immunogenicity of multiple doses of an intranasal vaccine using bovine parainfluenza virus type 3 (bPIV3).

METHODS

One hundred ninety-two healthy 2-month-old infants were randomized 1 : 1 : 1 to receive 1x10(5) median tissue culture infective dose (TCID(50)) bPIV3 vaccine, 1x10(6) TCID(50) bPIV3 vaccine, or placebo at 2, 4, 6, and 12-15 months of age. Safety information was collected by use of diary sheets and telephone interviews. Nasal wash and serum specimens were collected for assessment of infectivity and immunogenicity.

RESULTS

The safety profiles of both dosages of bPIV3 were similar to that of placebo, with the exception of fever with temperature of >/=38.1 degrees C after dose 2 only, occurring in 34% of the 1x10(5) TCID(50) group, 35% of the 1x10(6) TCID(50) group, and 12% of the placebo group (P<.01). No vaccine-related serious adverse events were reported. The cumulative vaccine infectivity (isolation of bPIV3 and/or bPIV3 seroconversion) after dose 3 was similar in the 2 vaccine groups (87% in the 1x10(5) TCID(50) group and 77% in the 1x10(6) TCID(50) group) (P=.46). Seroconversion rates after dose 3, assessed by means of hemagglutination inhibition assay, after adjustment for decrease in maternal antibody titers, were 67% in the 1x10(5) TCID(50) group, 57% in the 1x10(6) TCID(50) group, and 12% in the placebo group (P<.01). Isolation of bPIV3 was common after dose 1, dose 2, or dose 3, but only 1 of 51 participants in the vaccine groups had bPIV3 isolated after dose 4.

CONCLUSIONS

Multiple doses of bPIV3 vaccine were well tolerated and immunogenic in young infants.

Compliance with national immunization guidelines for children younger than 2 years, 1996-1999

OBJECTIVES

To evaluate compliance with national immunization guidelines among a large cohort of children cared for at health maintenance organizations (HMOs) and to examine effects on immunization status.

METHODS

A cohort study of 176134 children born between January 1, 1994, and December 31, 1997, and monitored from birth to the second birthday was performed. Subjects belonged to the Vaccine Safety Datalink Project, a study of children enrolled in 1 of 4 HMOs. Children were continuously enrolled in a HMO for the first 2 years of life. Prevailing recommendations regarding optimal ages of immunization and intervals between doses were applied to define appropriate immunization timing and immunization status. Noncompliance was defined as having a missing or late immunization or an immunization error. Immunization errors included invalid immunizations (too early to be acceptable), extra immunizations (superfluous immunizations or make-up immunizations for invalid immunizations), and missed opportunities resulting in late or missing immunizations.

RESULTS

Although 75.4% of children in these HMOs were up to date for all immunizations at 2 years, only 35.6% of children were fully compliant with recommended immunization practices. Less than 8% of children received all immunizations in accordance with strict interpretation of recommended guidelines. Fifty-one percent of children had at least 1 immunization error by age 2 years; 29.7% had a missed opportunity with subsequent late or missing immunization, 20.4% had an invalid immunization, and 11.6% had an extra immunization. Common reasons for noncompliance included missed opportunities for the fourth Haemophilus influenzae type b vaccine (14.6%), invalid fourth diphtheria-tetanus-pertussis/acellular pertussis immunizations (11.0%), and superfluous polio immunizations (9.8%).

CONCLUSIONS

Approximately 35.6% of children were compliant with prevailing childhood immunization recommendations from 1996 to 1999. Efforts to improve compliance with guidelines are recommended, to optimize childhood infectious disease prevention.

Acellular pertussis vaccines and complement killing of Bordetella pertussis

Antibody-dependent complement killing of Bordetella pertussis after immunization with a three-component acellular pertussis vaccine was characterized. Postimmunization activity was unchanged for about half of the adult vaccine recipients. The responses of the other individuals were complex, with evidence of both beneficial and antagonistic responses occurring, sometimes in the same individual.

Incidence of Haemophilus influenzae type b and other invasive diseases in South Korean children

To determine incidence of invasive Haemophilus influenzae type b (Hib) disease in a defined population of Jeonbuk Province, Korea, children <5 years were evaluated in prospective, population-based surveillance of invasive bacterial diseases using standardized methods for patient referral, clinical evaluation and laboratory testing (optimized culture, latex agglutination, polymerase chain reaction). Vaccine utilization was assessed with vaccination histories of patients in surveillance, monthly data on Hib vaccine distribution and a coverage survey of clinic patients in study population. From September 1999 to December 2001, 2176 children were evaluated for possible meningitis, 1541 had no cerebrospinal fluid (CSF) findings of meningitis, 605 had CSF abnormalities (suspected bacterial meningitis) but no pathogen identified; six patients had probable Hib meningitis and eight had confirmed Hib meningitis. The annual suspected bacterial meningitis incidence was 258.4/100,000 <5 years and the probable/confirmed Hib meningitis incidence was 6.0/100,000 <5 years. Pneumococcal meningitis incidence was 2.1/100,000 <5 years and Group B streptococcal meningitis incidence was 0.17/1000 live births. A total of 69,589 Hib vaccine doses were distributed during the study. Hib vaccine coverage was negligible initially but increased to 16% (complete Hib immunization) and 27% (partial immunization) in final months of study. Suspected bacterial meningitis incidence was high but proven invasive Hib meningitis incidence was low. Hib was leading cause of bacterial meningitis yet bacterial pathogens were identified in only 4% of abnormal CSF. These findings may reflect truly low incidence, presumptive antibiotic treatment, partial Hib immunization, or incomplete clinical evaluations. Given the apparent Hib meningitis burden in Jeonbuk Province, additional studies to describe other invasive Hib syndromes, Hib-associated mortality and disability, and economic impact of Hib disease will be useful to guide public health decisions regarding routine Hib vaccine introduction.

Immune responses and antibody decay after immunization of adolescents and adults with an acellular pertussis vaccine: the APERT Study

As part of a prospective acellular pertussis (ACP) vaccine efficacy trial, 5 serum samples were obtained, over an 18-month period, from 101 ACP-vaccine recipients and 99 control subjects, to assess ACP antibody response and decay. Immunoglobulin (Ig) G and IgA antibodies to pertussis toxin (PT), filamentous hemagglutinin (FHA), pertactin (PRN), and fimbriae 2/3 (FIM) were measured by enzyme-linked immunosorbant assay, and titers of agglutinin were determined. Of the subjects, 16%-19% had preimmunization values of antibodies to PT that were above the assay's limit of quantitation (LOQ); in contrast, 36%-63% of the subjects had preimmunization values of antibodies to FHA, PRN, or FIM that were above the LOQ. Substantial increases in titers of IgG and IgA antibodies to the 3 ACP antigens (PT, FHA, and PRN) were observed. Over the 18-months, the percent decay in IgG and IgA antibodies ranged from 56% to 73% and from 57% to 70%, respectively; the IgG antibody response and decay suggests that geometric mean titers likely remain above the LOQ for 2-9 years and above the threshold of detection for 4-13 years. These findings support the use of ACP booster immunizations for adolescents and adults, to provide sustained levels of antibody.

Lack of association between hepatitis B birth immunization and neonatal death: a population-based study from the vaccine safety datalink project

BACKGROUND

There have been no population-based studies of the potential association between neonatal death and newborn immunization with hepatitis B vaccine (HBV).

METHODS

As part of the Vaccine Safety Datalink Project, we defined a birth cohort at Southern and Northern California Kaiser Permanente Health Plans of more than 350,000 live births from 1993 to 1998 and ascertained all deaths occurring under 29 days of age. We compared the proportions of deaths among birth HBV-vaccinated and unvaccinated newborns and reviewed the causes and circumstances of their deaths. We performed detailed clinical reviews of all HBV-vaccinated neonates who died and a sample of unvaccinated neonates who died and who were matched to vaccinated deaths for days of life, sex, birth year and site of care. To avoid confounding, we categorized the causes of death as either "expected" or "unexpected" and performed a stratified analysis to compare mortality with immunization status.

RESULTS

There were 1363 neonatal deaths during the study period. Whereas 67% of the entire birth cohort received HBV at birth, only 72 (5%) of the neonates who died were HBV-vaccinated at birth (P < 0.01). We found no significant difference in the proportion of HBV-vaccinated (31%) and unvaccinated (35%) neonates dying of unexpected causes (P = 0.6). Further we could not identify a plausible causal or temporal relationship between HBV administration and death for the 22 vaccinated neonates who died unexpectedly.

CONCLUSIONS

A relationship between HBV and neonatal death was not identified.

Evaluation of strategies for use of acellular pertussis vaccine in adolescents and adults: a cost-benefit analysis

Pertussis is increasingly recognized as a source of infection in adults who then commonly infect young children. Immunity to illness caused by Bordetella pertussis is not long-lived, so optimal control of pertussis may require booster immunizations. In a cost-benefit analysis, we evaluated the benefits of 7 independent strategies for administering a pertussis booster, in the form of a diphtheria-tetanus-acellular pertussis vaccine, to adolescents and adults. Break-even vaccine costs for each strategy were calculated by dividing costs preventable by vaccine by the number of persons eligible for vaccination. Of these strategies, the most economical would be to immunize adolescents 10-19 years of age, which would prevent 0.7-1.8 million pertussis cases and save 0.6 dollars-1.6 billion dollars over a decade. Although justified by our analysis, routine adult booster vaccinations every decade would be more expensive and more difficult to implement. A recommendation for booster vaccinations every 10 years requires more information about duration of immunity, program costs, compliance, and nonmedical costs associated with pertussis.

Antibody-mediated neutralization of pertussis toxin-induced mitogenicity of human peripheral blood mononuclear cells

Antibody-mediated neutralization of pertussis toxin-induced proliferation of human peripheral blood mononuclear cells (PBMC) was assessed using alamarBlue and compared with results from the Chinese hamster ovary (CHO) cell assay using sera from vaccinated adults and convalescent children. Neutralization values for the CHO assay were similar for vaccinated and convalescent subjects; however. the convalescent group had higher titers in the PBMC assay. Results for pertussis toxin neutralization with the CHO assay appear to be distinct from those with the PBMC assay.

Heptavalent pneumococcal vaccine conjugated to outer membrane protein of Neisseria meningitidis serogroup b and nasopharyngeal carriage of Streptococcus pneumoniae in infants

BACKGROUND

Streptococcus pneumoniae (Sp) is an important bacterial pathogen in children. Nasopharyngeal (NP) colonization of S. pneumoniae is necessary for person-to-person transmission and often precedes invasive disease.

METHODS

NP carriage of Sp was studied in 49 infants following administration of a heptavalent pneumococcal conjugate vaccine (PCV) conjugated to the outer membrane protein of serogroup b Neisseria meningitidis (vaccine serotypes: 4, 6B, 9V, 14, 18C, 19F, 23F). The vaccine was administered at 2, 4, 6, and 12 months of age and carriage rates were compared to a concurrent group of 32 infants not given PCV and evaluated over the first 15 months of life.

RESULTS

Overall, Sp was isolated in 86/367 (23%) of NP cultures and 49% of infants. Serotype 23F was significantly less prevalent in the PCV group (1.9%) than the control group (16.1%) (P<0.05). Analysis of the proportion of children with prevalent carriage or acquisition of carriage did not differ between groups when evaluated by age or serotype. We noted, however, decreased acquisition and carriage in the vaccine group 1 month following the 12 month dose of PCV for vaccine serotypes (76 and 52% reduction, respectively), but this did not reach statistical significance (P=0.3). Adjustment for age, daycare and antibiotic use by multivariate modeling revealed no difference in carriage of vaccine containing serotypes or non-vaccine serotypes between groups.

CONCLUSION

We did not show a significant effect of this heptavalent PCV on NP carriage. Further study of this issue, including a larger population size, is needed.

Safety and immunogenicity of a heptavalent pneumococcal conjugate vaccine in infants

OBJECTIVE

To evaluate the safety and immunogenicity of two lots of a heptavalent Streptococcus pneumoniae conjugate vaccine (PCV) containing seven capsular polysaccharide serotypes (4, 6B, 9V, 14, 18C, 19F, and 23F) conjugated to the outer membrane complex of Neisseria meningitidis serogroup B (OMPC) and administered to infants at 2, 4, 6, and 12 months of age.

METHODS

One hundred twenty infants were randomly assigned to concurrently receive PCV-OMPC and one of two Haemophilus influenzae type b (Hib) conjugate-DTwP combination vaccines: (1) Hib with a heterologous protein carrier (CRM(197), TETRAMUNE, Group 1) or (2) an experimental Hib-hepatitis b combination vaccine with the homologous carrier (OMPC, Group 2). All infants in Groups 1 and 2 received PCV-OMPC (lot 1) at 12 months of age. Another separate group of 120 infants (Group 3) received a different lot of PCV-OMPC concurrently with Hib-CRM(197) (TETRAMUNE) at 2, 4, and 6 months of age and then were randomized to receive either PCV-OMPC or a 23-valent polysaccharide (PS) pneumococcal vaccine at 12 months of age.

RESULTS

Each PCV-OMPC lot was generally well tolerated and no vaccine-related serious adverse events were reported. Following the primary series, serotype-specific anti-pneumococcal geometric mean concentrations (GMC) were highest for serotypes 14, 19F, and 4 and lowest for serotypes 6B and 23F. GMC and seroconversion rates in Group 3 (lot 2) were lower than in Group 1 (lot 1) for serotypes 6B, 14, 18C, and 23F. Antibody responses to serotypes 6B, 14, and 18C were significantly lower in Group 2 compared to Group 1. Following a booster dose of PCV-OMPC at 12 months of age, each lot was immunogenic with at least a 5-10-fold increase in antibody levels, and responses were significantly higher among those who received the PS vaccine.

CONCLUSIONS

PCV-OMPC is generally safe in infants, displays variable immune response by serotype, and concomitant receipt of Hib vaccine with homologous carrier may impact on its immunogenicity.

Polio extraimmunization in children younger than 2 years after changes in immunization recommendations

OBJECTIVE

To investigate trends over time in polio extraimmunization among children in 4 large health maintenance organizations and to study the association with recent changes in polio immunization policy.

METHODS

Using 176 169 children who were born after 1994 and enrolled for their first 2 years of life, we assessed rates and trends of polio extraimmunization in the Vaccine Safety Datalink project. We used logistic regression to test the association of extraimmunization with different polio immunization schedules and with sociodemographic characteristics and used Poisson regression to test changes in rates over time.

RESULTS

Overall, 10.5% were extraimmunized for poliovirus; children on the all inactivated polio virus or sequential schedule were one half as likely as those on the all oral polio virus schedule to be extraimmunized by 2 years of age. There was a significant decrease in extraimmunization over time, with <5% of children born at the end of 1997 being extraimmunized, compared with >15% at the beginning of 1994.

CONCLUSIONS

Poliovirus extraimmunization rates have fallen dramatically in association with the change-over to the all inactivated polio virus schedule.

Safety and immunogenicity of a combination diphtheria-tetanus toxoids-acellular pertussis-hepatitis B vaccine administered at two, four and six months of age compared with monovalent hepatitis B vaccine administered at birth, one month and six months of age

OBJECTIVE

To evaluate the safety and immunogenicity of diphtheria-tetanus toxoids-acellular pertussis (DTPa)-hepatitis B (HepB) combination vaccine given at 2, 4 and 6 months of age compared with monovalent HepB vaccine given at birth, 1 month and 6 months of age and DTPa vaccine given at 2, 4 and 6 months of age.

METHODS

Healthy infants were randomized to receive a combination DTPa-HepB vaccine (diphtheria and tetanus toxoids, acellular pertussis antigens and hepatitis B surface antigen), concomitantly with type b and oral poliovirus vaccines at 2, 4 and 6 months of age (Group 1) or HepB vaccine given at birth, 1 month and 6 months of age and DTPa, type b and oral poliovirus vaccines given at 2, 4 and 6 months of age (Group 2). Antibody responses were evaluated at birth, 2 months and 7 months of age. Safety was evaluated after each immunization using diary cards and parental interviews.

RESULTS

One month after the third dose (7 months of age), the geometric mean concentration of antibody to hepatitis B surface antigen was approximately 3.5-fold higher in Group 2 than in Group 1 infants (3643 and 1052 mIU/ml, respectively; < 0.001). Nevertheless the rates of seroprotection to HepB (antibody to hepatitis B surface antigen > or =10 mIU/ml) in Groups 1 and 2 were similar, 99 and 100%, respectively. Also the postvaccination geometric mean concentrations and rates of seroprotection or vaccine response to all of the other vaccine antigens evaluated were similar or greater in Group 1 than in Group 2. The rates of adverse events were similar between the two groups, with fussiness and soreness at any injection site reported most frequently.

CONCLUSIONS

The DTPa-HepB combination vaccine was safe and immunogenic when given to infants at 2, 4 and 6 months of age. Equivalent rates of seroprotection to hepatitis B were achieved despite a reduction of the interval between the second and third doses from 5 months in Group 2 to 2 months in Group 1. Hepatitis B-containing combination vaccines should reduce the number of vaccine injections required in childhood and maintain excellent seroprotection against multiple pathogens.

Childhood vaccinations and risk of asthma

BACKGROUND

A few previous studies have suggested that childhood vaccines, particularly whole cell pertussis vaccine, may increase the risk of asthma. We evaluated the suggested association between childhood vaccinations and risk of asthma.

METHODS

Cohort study involving 167,240 children who were enrolled in 4 large health maintenance organizations during 1991 to 1997, with follow-up from birth until at least 18 months to a maximum of 6 years of age. Vaccinations were ascertained through computerized immunization tracking systems, and onset of asthma was identified through computerized data on medical care encounters and medication dispensings.

RESULTS

In the study 18,407 children (11.0%) developed asthma, with a median age at onset of 11 months. The relative risks (95% confidence intervals) of asthma were: 0.92 (0.83 to 1.02) for diphtheria, tetanus and whole cell pertussis vaccine; 1.09 (0.9 to 1.23) for oral polio vaccine; 0.97 (0.91 to 1.04) for measles, mumps and rubella (MMR) vaccine; 1.18 (1.02 to 1.36) for Haemophilus influenzae type b (Hib); and 1.20 (1.13 to 1.27) for hepatitis B vaccine. The Hib result was not consistent across health maintenance organizations. In a subanalysis restricted to children who had at least 2 medical care encounters during their first year, the relative risks decreased to 1.07 (0.71 to 1.60) for Hib and 1.09 (0.88 to 1.34) for hepatitis B vaccine.

CONCLUSION

There is no association between diphtheria, tetanus and whole cell pertussis vaccine, oral polio vaccine or measles, mumps and rubella vaccine and the risk of asthma. The weak associations for Hib and hepatitis B vaccines seem to be at least partially accounted for by health care utilization or information bias.

Kinetics of maternal hepatitis a antibody decay in infants: implications for vaccine use

We conducted a seroepidemiologic study to evaluate the kinetics of maternal hepatitis A antibody decay in infants. Serum samples obtained from 200 infants at 2 and 4 months of age were tested for hepatitis A antibody. Seventy-six infants (38%) were hepatitis A antibody-positive with a geometric mean antibody titer of 2634 mIU/ml. Samples collected at 4, 6 and/or 12 months of age showed seropositivity rates of 100, 95 and 39%, respectively. These data indicate that maternal antibody levels remained high through the first 6 months of life but decayed significantly by 12 months of age.

Lack of association between rotavirus infection and intussusception: implications for use of attenuated rotavirus vaccines

BACKGROUND

Withdrawal of the tetravalent rhesus-human rotavirus vaccine Rotashield because of its association with intussusception raised concerns about a potential link between natural rotavirus disease and intussusception. Our objective was to determine whether such an association exists.

METHODS

In the Southern California Kaiser Permanente Health Care Plan, a large health maintenance organization, from October, 1992, to July, 1999, we retrospectively identified by computerized data and medical charts all children <3 years old with intussusception, and from 1997 to 1999 we independently identified by prospective clinical and laboratory evaluation children <3 years old with rotavirus diarrhea. We compared the epidemiologic characteristics of intussusception and rotavirus infection in our study population and evaluated for the presence of both diseases in individual patients.

RESULTS

Using computerized data we identified 124 cases of intussusception, 101 (81%) of which were confirmed by medical chart and radiologic reviews. The incidences for infants <1 year old and for children <3 years old were 41 (95% confidence interval, 32 to 55) and 17 (95% confidence interval, 13 to 20) per 100,000 child years, respectively. Between November 1997 and July 1999, we identified 470 cases of rotavirus diarrhea and none had intussusception. Although rotavirus diarrhea had a distinct peak incidence between December and February, intussusception had no apparent seasonality. The age distributions overlapped, but intussusception occurred at an earlier age than rotavirus disease.

CONCLUSIONS

We found no epidemiologic evidence for an association between intussusception and natural rotavirus infection, but our study was limited by an insufficient number of cases to definitively exclude a causal link. The dramatic winter peak of rotavirus disease had no discernable parallel in the incidence of intussusception. Our data suggest that the association between tetravalent rhesus-human rotavirus vaccine and intussusception may possibly result from the nonhuman rotavirus components of that vaccine.

Evaluation of Chlamydia pneumoniae and Mycoplasma pneumoniae as etiologic agents of persistent cough in adolescents and adults

Chlamydia pneumoniae and Mycoplasma pneumoniae were evaluated as agents of persistent cough in adolescents and adults (n = 491). Tests of 473 respiratory specimens by culture or PCR or both identified four episodes (0.8%) of M. pneumoniae-associated illness and no episodes of C. pneumoniae illness, suggesting that these bacteria do not frequently cause persistent cough.

Childhood vaccinations, vaccination timing, and risk of type 1 diabetes mellitus

OBJECTIVES

To evaluate suggested associations between childhood vaccinations, particularly against hepatitis B and Haemophilus influenzae type b, and risk of developing type 1 diabetes; and to determine whether timing of vaccination influences risk.

METHODS

We conducted a case-control study within 4 health maintenance organizations (HMOs) that participate in the Vaccine Safety Datalink project of the Centers for Disease Control and Prevention. Study eligibility was restricted to children who met the following criteria: 1) born during 1988 through 1997; 2) HMO member since birth; 3) continuously enrolled for first 6 months of life; and 4) at least 12 months of HMO membership before diabetes incidence date (or index date for controls) unless incidence date was before 12 months of age. All 4 HMOs maintain registries of their members who have diabetes, and we used the registries to identify potential cases of diabetes. We conducted chart reviews to verify that potential cases met the World Health Organization epidemiologic case definition for type 1 diabetes mellitus (ie, a physician's diagnosis of diabetes plus treatment with daily insulin injections). We defined the incidence date of diabetes as the first date that the child received a diagnosis of diabetes. We attempted to match 3 controls to each case. Controls had the same eligibility criteria as cases and were matched to individual cases on HMO, sex, date of birth (within 7 days), and length of health plan enrollment (up to the incidence or index date). The index date for controls was defined as the incidence date of the case to which the control was matched. Chart abstraction was performed by trained chart abstractors using standardized forms. In addition to complete vaccination histories, the chart abstraction forms for both cases and controls included information on sociodemographic characteristics, selected medical conditions, history of breastfeeding, and family medical history. We used conditional logistic regression to estimate the odds ratio (OR) of diabetes associated with vaccination, with vaccine exposure defined as before the diabetes incidence date (or index date for controls).

RESULTS

Two hundred fifty-two confirmed cases of diabetes and 768 matched controls met the study eligibility criteria. The OR (95% confidence interval) for the association with type 1 diabetes was 0.28 (0.07-1.06) for whole cell pertussis vaccine (predominantly in combination as diphtheria, tetanus toxoids and pertussis vaccine), 1.36 (0.70-2.63) for measles-mumps-rubella, 1.14 (0.51-2.57) for Haemophilus influenzae type b, 0.81 (0.52-1.27) for hepatitis B vaccine, 1.16 (0.72-1.89) for varicella vaccine, and 0.92 (0.53-1.57) for acellular pertussis-containing vaccines. Compared with children who had not received hepatitis B vaccine, the OR of diabetes was 0.51 (0.23-1.15) for children vaccinated at birth and 0.86 (0.54-1.35) for those first vaccinated against hepatitis B at 2 months of age or later. Race and ethnicity and family history of diabetes were independently associated with risk of type 1 diabetes, but adjustment for these factors did not materially alter the ORs for any of the vaccines.

CONCLUSIONS

In this large, population-based, case-control study, we did not find an increased risk of type 1 diabetes associated with any of the routinely recommended childhood vaccines. Our study adds to previous research by providing data on newer vaccines, including hepatitis B, acellular pertussis, and varicella vaccines. For the older vaccines, our results are generally in agreement with previous studies in not finding any increased risks. Ours is the first epidemiologic study to evaluate the possibility that timing of vaccination is related to risk of clinical diabetes in children. Our results on hepatitis B vaccine do not support the hypothesis; risk of type 1 diabetes was not different between infants vaccinated at birth and those who received their first vaccination later in life. The results of our study and the preponderance of epidemiologic evidence do not support an association between any of the recommended childhood vaccines and an increased risk of type 1 diabetes. Suggestions that diabetes risk in humans may be altered by changes in the timing of vaccinations also are unfounded.

Strategies for development of combination vaccines

BACKGROUND

The increasing complexity of the recommended childhood immunization schedule has resulted in the need for combination vaccines.

METHODS

Through an extensive review of the current literature, various strategies and issues related to the development of combination vaccines are discussed.

RESULTS

Issues that should be considered when combining vaccine components include the current childhood immunization schedule, compatibility of components, availability of antigens for targeted diseases, safety, efficacy, immunogenicity and route of delivery. When choosing an appropriate combination of antigen(s)/serotype(s) for a global or national formulation, careful consideration must be made when selecting serotypes to combine depending on the market or area of use. It is important to know that potential interactions can involve other components of the vaccines, including buffers, adjuvants and preservatives. The Food and Drug Administration requires that the combination not only have immunogenicity comparable with those of the component vaccines, but that its safety profile be comparable with the most reactogenic component. The Food and Drug Administration also recommends that a test of noninferiority be performed, such that the combination performs similarly to the separate components with regard to antibody titers.

CONCLUSIONS

Combination vaccines are critical to the success of vaccination programs, and each new combination must be carefully studied to ensure comparable safety and immunogenicity of the individual components.

Safety and immunogenicity of a pentavalent diphtheria, tetanus, pertussis, hepatitis B and polio combination vaccine in infants

INTRODUCTION

The objectives of this study were to evaluate the safety and immunogenicity of a new combination vaccine (DTaP-HB-IPV) containing diphtheria, tetanus, acellular pertussis and hepatitis B (HB) and a new inactivated poliovirus vaccine (IPV) manufactured by GlaxoSmithKline (GSK). This vaccine was given in an all IPV or sequential IPV and oral polio vaccine (OPV) schedule. Another combination vaccine, DTaP-HB (GSK), was similarly evaluated given with OPV or IPV.

METHODS

Four hundred infants were randomized into one of four study groups and immunized at 2, 4 and 6 months of age. Group A received three doses of DTaP-HB-IPV; Group B received DTaP-HB-IPV at 2 and 4 months and DTaP-HB with OPV (Orimune) at 6 months; Group C received three doses of DTaP-HB with licensed IPV (IPOL) administered separately; Group D received separate doses of OPV, DTaP (Infanrix; GSK) and HB (Engerix; GSK). All subjects received conjugate Haemophilus influenzae type b vaccine (Hib) (OmniHIB) at 2, 4 and 6 months of age given at a separate injection site. Subjects who returned at 12 to 18 months of age (229) received booster immunization with DTaP and Hib. Safety was evaluated after each vaccine dose. Blood was drawn before the first dose and one month after the third dose as well as before and after the booster dose.

RESULTS

There were no vaccine-related serious adverse events in any group after any vaccine dose. Minor systemic and local adverse events were also not significantly different among the four groups after any dose. There were no differences in the immune response rates for Hib, HB, polio (types 1, 2 and 3), diphtheria, tetanus or pertussis antigens (pertussis toxin, filamentous hemagglutinin, pertactin) among groups, although there were some quantitative differences in specific antibody titers among groups. DTaP-HB-IPV and DTaP-HB combination vaccines had safety and immunogenicity equivalent to those of standard individually administered vaccines. The new IPV was not inferior to IPOL.

CONCLUSION

Use of the pentavalent combination vaccine would greatly reduce the number of required injections during the first 2 years of life, thereby simplifying the immunization schedule, enhancing compliance and facilitating acceptance of additional injections engendered by introduction of newer vaccines.

Antibody responses to bovine parainfluenza virus type 3 (PIV3) vaccination and human PIV3 infection in young infants

A phase 2 clinical trial was conducted to evaluate the antibody responses to bovine parainfluenza virus type 3 (bPIV3) vaccination in young infants. Three groups were tested as follows: placebo (n=66) and 10(5) (n=64) or 10(6) (n=62) TCID(50) of bPIV3. The vaccine or placebo was administered intranasally at ages 2, 4, 6, and 12-15 months, and serum specimens were collected at ages 2, 6, 7, 12-15, and 13-16 months. Serum hemagglutination inhibition (HI) and IgA antibody titers against bPIV3 and human PIV3 (hPIV3) were measured. The results indicate that antibody responses to bPIV3 vaccination are more likely to be detected by the bPIV3 IgA and HI assays than by the hPIV3 IgA and HI assays, that bPIV3-induced antibody response can be differentiated from hPIV3-induced antibody response most reliably by comparing bPIV3 and hPIV3 HI titers, and that bPIV3 vaccine prevents vaccine recipients from developing antibody profiles of hPIV3 primary infection.

The risk of seizures after receipt of whole-cell pertussis or measles, mumps, and rubella vaccine

BACKGROUND

The administration of the diphtheria and tetanus toxoids and whole-cell pertussis (DTP) vaccine and measles, mumps, and rubella (MMR) vaccine has been associated with adverse neurologic events, including seizures. We studied the relation between these vaccinations and the risk of a first seizure, subsequent seizures, and neurodevelopmental disability in children.

METHODS

This cohort study was conducted at four large health maintenance organizations and included reviews of the medical records of children with seizures. We calculated the relative risks of febrile and nonfebrile seizures among 679,942 children after 340,386 vaccinations with DTP vaccine, 137,457 vaccinations with MMR vaccine, or no recent vaccination. Children who had febrile seizures after vaccination were followed to identify the risk of subsequent seizures and other neurologic disabilities.

RESULTS

Receipt of DTP vaccine was associated with an increased risk of febrile seizures only on the day of vaccination (adjusted relative risk, 5.70; 95 percent confidence interval, 1.98 to 16.42). Receipt of MMR vaccine was associated with an increased risk of febrile seizures 8 to 14 days after vaccination (relative risk, 2.83; 95 percent confidence interval, 1.44 to 5.55). Neither vaccination was associated with an increased risk of nonfebrile seizures. Analyses of automated data alone gave results similar to the analyses of the data from medical-record reviews. The number of febrile seizures attributable to the administration of DTP and MMR vaccines was estimated to be 6 to 9 and 25 to 34 per 100,000 children, respectively. As compared with other children with febrile seizures that were not associated with vaccination, the children who had febrile seizures after vaccination were not found to be at higher risk for subsequent seizures or neurodevelopmental disabilities.

CONCLUSIONS

There are significantly elevated risks of febrile seizures on the day of receipt of DTP vaccine and 8 to 14 days after the receipt of MMR vaccine, but these risks do not appear to be associated with any long-term, adverse consequences.

Prospective, randomized, placebo-controlled evaluation of the safety and immunogenicity of three lots of intranasal trivalent influenza vaccine among young children

BACKGROUND

Trivalent formulations of an experimental, cold-adapted, intranasal influenza (CAIV) vaccine have been shown to be safe, immunogenic and efficacious in young children.

METHODS

We evaluated the safety and immunogenicity of three consistency lots of CAIV in children 12 to 36 months of age randomized to one of five groups: Groups 1, 2 and 3 received separate lots containing A/Shenzhen/227/95 (H1N1), A/Wuhan/359/95(H3N2) and B/Harbin/7/94-like viral strains. Group 4 received an earlier efficacy trial lot which included a different H1N1 strain (A/Texas/36/91-like); and Group 5 received placebo. We performed strain-specific serum hemagglutination inhibition antibody levels against type A (H3N2 or H1N1) or type B as appropriate.

RESULTS

Overall 474 children received 2 doses, 2 months apart. Each lot was well-tolerated, and there were no significant group differences between consistency lots in the proportion of children with fever and local or systemic reactions after vaccination. The 3 consistency lots were not statistically different with regard to immunogenicity as measured by seroconversion or absolute geometric mean titer. Immune responses were more robust among initially seronegative children and for H3N2 and B strains than for H1N1 strains. After 2 doses of vaccine 97, 84 and 62% had hemagglutination inhibition titers > or = 1/32 against A/H3N2, B and H1N1 strains, respectively. For A/H3N2 only, immune responses after 1 dose of vaccine are similar to those seen after 2 doses.

CONCLUSIONS

Each consistency lot of CAIV is as or more immunogenic than a lot used in a large efficacy trial.

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.

Does influenza vaccination prevent asthma exacerbations in children?

OBJECTIVE

Influenza can exacerbate asthma, particularly in children. The effectiveness of influenza vaccine in preventing influenza-related asthma exacerbations, however, is not known. We evaluated influenza vaccine effectiveness in protecting children against influenza-related asthma exacerbations.

STUDY DESIGN

We conducted a population-based retrospective cohort study with medical and vaccination records in 4 large health maintenance organizations in the United States during the 1993-1994, 1994-1995, and 1995-1996 influenza seasons. We studied children with asthma who were 1 through 6 years of age and who were identified by search of computerized databases of medical encounters and pharmacy dispensings. Main outcome measures were exacerbations of asthma evaluated in the emergency department or hospital.

RESULTS

Unadjusted rates of asthma exacerbations were higher after influenza vaccination than before vaccination. After adjustment was done for asthma severity by means of a self-control method, however, the incidence rate ratios of asthma exacerbations after vaccination were 0.78 (95% CI: 0.55 to 1.10), 0.59 (0.43 to 0.81), and 0.65 (0.52 to 0.80) compared with the period before vaccination during the 3 influenza seasons.

CONCLUSIONS

After controlling for asthma severity, we found that influenza vaccination protects against acute asthma exacerbations in children.

Immunogenicity of a Haemophilus influenzae type b-tetanus toxoid conjugate vaccine when mixed with a diphtheria-tetanus-acellular pertussis-hepatitis B combination vaccine

BACKGROUND

Combination vaccines are urgently needed to reduce the number of injections given to young children. The aim of the study was to evaluate the safety and immunogenicity of a combination vaccine that contains diphtheria and tetanus toxoids and acellular pertussis antigens (DTaP), recombinant hepatitis B surface antigen (HepB) and Haemophilus influenzae type b (Hib) polysaccharide conjugated to tetanus toxoid (PRP-T).

METHODS

Four hundred five infants were randomized equally to three groups and immunized at 2, 4 and 6 months of age with: (1) DTaP/HepB vaccine used to reconstitute lyophilized PRP-T vaccine and administered as a single injection; (2) DTaP/HepB vaccine and PRP-T vaccine administered as two separate injections; or (3) DTaP, HepB and PRP-T vaccines administered as three separate injections. Safety was closely monitored, and blood specimens were obtained to assess antibody responses to each vaccine antigen.

RESULTS

All study vaccines were well-tolerated, and the rates of systemic and injection site reactions were similar between groups. After the third dose the geometric mean antibody concentrations to Hib were significantly lower in subjects in Group 1 (1.63 microg/ml) compared with subjects in Groups 2 and 3 (6.26 and 6.15 microg/ml, respectively; P < 0.0001). Subjects with antibody concentrations <1.0 microg/ml after the third dose responded well to a booster dose of Hib conjugate vaccine given at 11 to 15 months of age (41 of 44 with anti-PRP > or = 1.0 microg/ml). Differences between groups for antibody responses to the other vaccine components were not clinically significant.

CONCLUSIONS

Infants given a combined DTaP/ HepB/PRP-T vaccine experienced a significantly lower antibody response to the PRP-T component than infants given PRP-T vaccine as a separate injection. However, the immune response to a booster dose of Hib conjugate vaccine indicated the presence of immunologic memory.

The incidence of Kawasaki syndrome in West Coast health maintenance organizations

BACKGROUND

Kawasaki syndrome (KS) causes an acute vasculitis of unknown etiology. It is a leading cause of acquired heart disease of children in Japan and the United States.

METHODS

We examined the incidence of KS in a well-defined population group of children < or =6 years of age, using data collected through the Vaccine Safety Datalink (VSD) project. The VSD database contains information on >1 million children enrolled in four West Coast health maintenance organizations (HMOs).

RESULTS

During 1993 through 1996 a total of 234 physician-diagnosed KS patients were reported in the 4 HMOs; 152 (65.0%) were boys and 195 (83.3%) were <5 years of age. The incidence of KS among children <5 years of age in the HMOs ranged from 9.0 to 19.1 per 100,000 person years. KS incidence was higher among boys in 3 of the sites. In the 2 sites with the highest number of KS patients, a seasonal occurrence of KS in winter and early spring was observed. Overall 226 (96.6%) of the KS patients were reported to have been hospitalized; hospitalization rates for children <5 years of age ranged from 9.0 to 16.8 per 100,000 person years.

CONCLUSIONS

The incidence of KS in the HMOs was similar to that reported in other population-based studies in the United States and higher than estimates for Australia and several European countries.

Does influenza vaccination exacerbate asthma? Analysis of a large cohort of children with asthma. Vaccine Safety Datalink Team

CONTEXT

Although influenza vaccination is recommended for children with asthma, only a minority are vaccinated. One reason for low influenza vaccine coverage among children with asthma may be concern that influenza vaccination may induce an exacerbation of asthma.

OBJECTIVE

To evaluate the safety of influenza vaccination in children with asthma, we studied the incidence of hospitalizations and emergency department visits for asthma following influenza vaccination.

DESIGN

Retrospective cohort study-analysis of population-based computerized medical and vaccination records.

SETTING

: Four large health maintenance organizations on the West Coast of the United States.

SUBJECTS

Children with asthma 1 through 6 years of age, identified by search of computerized databases of medical encounters and pharmacy prescriptions.

MAIN OUTCOME MEASURES

Exacerbations of asthma.

RESULTS

In unadjusted analyses vaccination was associated with high rates of asthma exacerbations. However, after adjusting for asthma severity using a self-control method, the incidence rate ratios of asthma exacerbations after vaccination were 0.58 (95% confidence interval, 0.36-0.95), 0.74 (95% confidence interval, 0.47-1.17), and 0.98 (95% confidence interval, 0.76-1.27) during the 3 influenza seasons.

CONCLUSIONS

After controlling for asthma severity, we found that influenza vaccination does not result in acute asthma exacerbations in children. Concern about possible exacerbation of asthma is not a valid reason to not vaccinate children with asthma against influenza.

Immunogenicity of a heptavalent pneumococcal conjugate vaccine in Apache and Navajo Indian, Alaska native, and non-native American children aged <2 years

High rates of invasive pneumococcal disease have been described among infants living in various Native American communities. In this study, we evaluated the immunogenicity of a 7-valent pneumococcal vaccine consisting of serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F covalently linked to the outer membrane protein complex of Neisseria meningitidis in Apache and Navajo Indian, Alaska Native, and non-Native American children. The vaccine was administered at ages 2, 4, and 6 months; a booster dose was given at age 15 months. Levels of serotype-specific immunoglobulin G (IgG) were measured by a standardized enzyme-linked immunosorbent assay. The responses after 3 primary doses of vaccine were similar in all 3 groups of children, except for those to serotypes 14 and 23F. One month after the booster dose, geometric mean concentrations (GMCs) of serotype-specific IgG antibodies increased significantly in all 3 groups of children, compared with GMCs of IgG antibodies to pneumococcal serotypes before the booster dose.

Influenza vaccination in children with asthma in health maintenance organizations. Vaccine Safety Datalink Team

We assessed vaccination coverage and predictors of influenza vaccination in asthmatic children in four large Health Maintenance Organizations. We studied 68,839 children with asthma at four Health Maintenance Organizations (HMOs) in the 1995-1996 influenza season and 34,032 children at two HMOs in the 1996-1997 influenza season. In both seasons only 9-10% were vaccinated against influenza. Children who were hospitalized, had an emergency department visit for asthma or a prescription for a beta-agonist prior to the influenza season, were more likely to be vaccinated. Overall, 61% of the unvaccinated asthmatic children had made an outpatient clinic visit during months when influenza vaccination would have been appropriate. Vaccination coverage could be increased by taking advantage of all opportunities to vaccinate children with asthma whenever they make clinic visits in the fall and early winter.

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.

Immunity to cross-reactive serotypes induced by pneumococcal conjugate vaccines in infants

Infants were immunized with 1 of the 3 experimental pneumococcal conjugate vaccines that contain 6B and 19F but not 6A or 19A serotypes. Their sera were studied for the capacity to opsonize Streptococcus pneumoniae 6A, 6B, 19A, and 19F serotypes and the level of IgG antibody to the 4 serotypes. Significant increases were observed in the number of infants with detectable opsonophagocytic titers with 3 conjugate vaccines for 6B (vaccine) serotype but with only 2 vaccines for 6A (cross-reactive) serotype. Significant increases were observed with 2 conjugate vaccines for 19F serotype but with only 1 vaccine for 19A serotype. Thus, some conjugate vaccines may elicit cross-protection better than others. In addition, correlations between opsonophagocytic titers and IgG antibody levels by ELISA were high for 6B and 19F serotypes but low for 6A and 19A serotypes. Thus, ELISA may be an inadequate surrogate assay of vaccine response for cross-reactive serotypes.

Epidemiology of diarrheal disease among children enrolled in four West Coast health maintenance organizations. Vaccine Safety Datalink Team

BACKGROUND

We used information from the Vaccine Safety Datalink (VSD) about approximately 1 million children enrolled in four health maintenance organizations to assess the morbidity from diarrhea and estimate the disease burden of rotavirus.

METHODS

We examined trends of diarrhea-associated hospitalizations and emergency room (ER) visits among VSD children ages 1 month through 4 years during October, 1992, through September, 1994 (two rotavirus seasons) and estimated the morbidity from rotavirus on the basis of characteristic patterns of age and seasonality.

RESULTS

Overall diarrhea was associated with 6.3% of hospitalizations and 4% of ER visits. During a child's first 5 years of life, we estimated that 1 in 57 was hospitalized and 1 in 21 required an ER visit because of diarrhea. Each year the number of diarrhea-associated hospitalizations and ER visits was greatest in winter among children ages 4 to 23 months and peaked in November in California and during February in Oregon and Washington. The winter seasonality of diarrhea-associated hospitalizations reflected the trends for diarrhea of presumed noninfectious and viral etiologies, which together accounted for most (92.9%) hospitalizations.

CONCLUSIONS

Diarrhea is an important cause of morbidity among VSD children. The epidemiologic patterns of diarrhea-associated hospitalizations and ER visits resembled those reported previously for rotavirus diarrhea, suggesting that rotavirus may be a major contributor to the overall morbidity from diarrhea. Enhanced surveillance by screening for rotavirus in a sample of children with diarrhea will permit a more accurate assessment of the disease burden of this pathogen and the cost effectiveness of a rotavirus immunization program.

Chlorhexidine gluconate (CHG) activity against clinical isolates of vancomycin-resistant Enterococcus faecium (VREF) and the effects of moisturizing agents on CHG residue accumulation on the skin

The effectiveness of skin decontamination by chlorhexidine gluconate (CHG) in the presence of commonly-used skin moisturizing lotions was evaluated using vancomycin-resistant Enterococcus faecium (VREF) as a representative nosocomial pathogen. Anti-bacterial efficacy was determined in vitro using pigskin preparations inoculated with five VREF clinical isolates to evaluate Calgon Vestal 2 and 4% (by weight) CHG solutions in comparison with Hibiclens Antiseptic Antimicrobial Cleaner (4% CHG solution). Control inocula were determined for each experiment from recovery of VREF harvested directly from the surface of each control piece of skin. These CHG formulations were evaluated in the presence and absence of Calgon Vestal 'Lotion Soft Skin Conditioner' (LSSC) to determine potential interactions of CHG with LSSC, and also with ¿Vaseline Intensive Care' lotion as a CHG-deactivating agent. The 2% Calgon Vestal CHG alone reduced VREF 10(2)-10(3)-fold, as well as 10(3)-10(4)-fold when LSSC was present, and was as efficacious as either 4% CHG solution when these were tested in the presence of LSSC. Four percent Calgon Vestal CHG produced reductions of 10(3)-10(5)-fold with or without LSSC present. Conversely, ¿Hibiclens' showed similar reductions in the presence of LSSC to that for the Calgon Vestal 4% CHG, but only a 10(1)-10(3)-fold reduction without LSSC. ¿Vaseline Intensive Care' lotion completely inactivated the VREF-killing effects for all of the CHG formulations tested, while LSSC and ¿Vaseline Intensive Care' lotion both showed minimal activity alone against these VREF isolates. These results indicate that the Calgon Vestal 2% CHG solution is as effective against VREF, even in the presence of LSSC, as either the 4% Calgon Vestal or Hibiclens 4% CHG formulations; the use of this lower concentration of CHG may be associated with less irritation, particularly with concomitant use of LSSC.

Vaccine Safety Datalink project: a new tool for improving vaccine safety monitoring in the United States. The Vaccine Safety Datalink Team

OBJECTIVE

To fill the large "gaps and limitations" in current scientific knowledge of rare vaccine adverse events identified in recent reviews of the Institute of Medicine.

METHODS

Computerized information on immunization, medical outcomes, and potential confounders on more than 500 000 children 0 to 6 years of age is linked annually at several health maintenance organizations to create a large cohort for multiple epidemiologic studies of vaccine safety.

RESULTS

Analysis of 3 years of follow-up data shows that 549 488 doses of diphtheria-tetanus-pertussis (DTP) and 310 618 doses of measles-mumps-rubella (MMR) vaccines have been administered to children in the study cohort. Analyses for associations between vaccines and 34 medical outcomes are underway. Screening of automated data shows that seizures are associated with receipt of DTP on the same day (relative risk [RR], 2.1; 95% confidence interval [CI], 1.1 to 4.0) and 8 to 14 days after receipt of MMR (RR, 3.0; 95% CI, 2.1 to 4.2). The diversity of vaccination exposures in this large cohort permits us to show that an apparent association of seizures 8 to 14 days after Haemophilus influenzae type b vaccine (RR, 1.6; 95% CI, 1.2 to 2.1) was attributable to confounding by simultaneous MMR vaccination; the association disappears with appropriate adjustment (RR, 1.0; 95% CI, 0.7 to 1.4).

CONCLUSION

Preliminary design, data collection, and analytic capability of the Vaccine Safety Datalink project has been validated by replication of previous known associations between seizures and DTP and MMR vaccines. The diversity in vaccine administration schedules permits potential disentangling of effects of simultaneous and combined vaccinations. The project provides a model of public health-managed care collaborations in addition to an excellent infrastructure for safety and other studies of vaccines.

Epidemiology of invasive pneumococcal disease in southern California: implications for the design and conduct of a pneumococcal conjugate vaccine efficacy trial

Population-based prospective surveillance of invasive pneumococcal disease was done in Southern California from 31 March 1992 to 1 April 1995; 814 cases were identified, for an incidence of 12.5/100,000 persons/year. The incidence among persons < or = 2, < or = 5, and > or = 65 years of age was 145, 72, and 32/100,000, respectively. More than 95% of cases included bacteremia; incidence of meningitis was 0.8/100,000. Among children < or = 2 years of age, 79% of isolates were obtained in the outpatient setting, compared with 16% of isolates among persons > or = 15 years of age. Eighty percent of isolates were serotypes included in heptavalent pneumococcal conjugate vaccines currently being evaluated. Children < or = 2 years of age were at highest risk of having an isolate resistant to penicillin. Among resistant isolates, high-level resistance increased from 4% to 21% over a 3-year period. Prospective epidemiologic data are needed to perform a protective efficacy trail of pneumococcal conjugate vaccines in infants, among whom most invasive pneumococcal disease is vaccine-preventable.

Comparative safety and immunogenicity of two recombinant hepatitis B vaccines given to infants at two, four and six months of age

OBJECTIVES

To evaluate the relative safety and immunogenicity of the two recombinant hepatitis B vaccines licensed in the United States with doses recommended for routine immunization of low risk infants and a schedule that corresponds with routine pediatric visits.

METHODS

Healthy infants were immunized at 2, 4 and 6 months of age with hepatitis B vaccine manufactured by either SmithKline Beecham (Engerix-B, 10 micrograms/dose, n = 228) or Merck and Co. (Recombivax HB, 2.5 micrograms/dose, n = 200). Adverse reactions were ascertained by parental reports and interviews and by review of medical records. Antibody concentrations to hepatitis B surface antigen (anti-HBs) were measured in sequential serum specimens by enzyme immunoassay.

RESULTS

Adverse reactions were mild and the rates were not significantly different between the two groups. After the first and second doses the rates of seropositivity (> or = 10 mIU/ml) and seroprotection (> or = 10 mIU/ml) were significantly higher in infants given SmithKline Beecham vaccine (P < 0.01). After the second and third doses infants given SmithKline Beecham vaccine also had significantly higher geometric mean anti-HBs concentrations compared with those given Merck vaccine (348.0 mIU/ml vs. 66.9 and 1914.8 mIU/ml vs. 514.8 mIU/ml, respectively, P < 0.001). Nevertheless after the third dose 99% of infants in both vaccine groups achieved seroprotective antibody concentrations.

CONCLUSIONS

Both recombinant hepatitis B vaccines were safe and immunogenic when administered concurrently with other pediatric vaccines at 2, 4 and 6 months of age, but earlier protective responses were observed with the SmithKline Beecham vaccine than with the Merck vaccine.

The use of Haemophilus influenzae type b-tetanus toxoid conjugate vaccine mixed with diphtheria-tetanus-pertussis vaccine in Gambian infants

In preparation for an efficacy trial of PRP-T Haemophilus influenzae type b conjugate vaccine, 251 Gambian infants were randomized to receive three doses of PRP-T and diphtheria-tetanus-pertussis (DTP) vaccines at 2, 3 and 4 months of age, either by separate injections, or combined in the same syringe. One month after the third dose, there was no difference between anti-PRP levels in those infants who received the vaccines separately (GMT 5.83 micrograms ml-1), and those who received the vaccines combined (GMT 5.57 micrograms ml-1). The proportions achieving levels of 1.0 microgram ml-1 were 89% and 92% in the "separate" and "combined" vaccine groups, respectively. There were no significant differences between groups in levels of antibody to diphtheria or tetanus. Geometric mean titres of antibody directed against pertussis antigens in the "separate" and "combined" groups were as follows: pertussis toxin 14.2 and 13.1 ELISA units (EU) ml-1; filamentous haemagglutinin 12.2 and 9.7 EU ml-1; pertactin 17.2 and 9.0 EU ml-1 (P < 0.05), fimbrial 2/3 antigens 449 and 364 EU ml-1. The combination of PRP-T and DTP in the syringe prior to administration is safe and immunogenic. The lower levels of anti-pertussis antibody are of unknown clinical significance.

Safety and immunogenicity of a recombinant hepatitis B vaccine administered to infants at 2, 4 and 6 months of age. The Kaiser-UCLA Vaccine Study Group

A recombinant hepatitis B vaccine was administered to over 5000 infants in a prospective, randomized and blinded study. Infants were given either recombinant hepatitis B vaccine (Engerix-B, SmithKline Beecham Pharmaceuticals, 10 micrograms dose-1) or a Haemophilus influenzae type b (Hib) conjugate vaccine at 2, 4 and 6 months of age simultaneously with diphtheria-tetanus-pertussis and oral polio vaccines. Adverse reactions were ascertained by parental reports and interviews, and review of medical records. Blood specimens collected from 269 infants given hepatitis B vaccine were assayed for antibody to hepatitis B surface antigen (anti-HBs) by enzyme immunoassay. Infants given hepatitis B vaccine experienced low rates of adverse reactions that were similar or lower than the rates in infants given Hib conjugate vaccine. The geometric mean anti-HBs concentrations were 9.6 mIU ml-1 after one dose, 333 mIU ml-1 after two doses and 1812 mIU ml-1 after three doses (99% had levels > or = 10 mIU ml-1). Antibody responses to diphtheria and tetanus toxoids were unaffected by simultaneous administration of hepatitis B or Hib conjugate vaccine. Engerix-B vaccine was safe and immunogenic when given with other routine childhood immunizations at 2, 4 and 6 months of age, and should provide long-term protection against hepatitis B virus infection.

Safety and immunogenicity of a serogroups A/C Neisseria meningitidis oligosaccharide-protein conjugate vaccine in young children. A randomized controlled trial

OBJECTIVE

To assess the safety and immunogenicity of a bivalent serogroups A/C meningococcal oligosaccharide-protein conjugate vaccine compared with the licensed meningococcal polysaccharide vaccine.

DESIGN

Randomized controlled trial.

STUDY POPULATION

Ninety healthy 18- to 24-month-old children who were seen at a southern California Kaiser Permanente clinic.

INTERVENTIONS

Vaccination with either the meningococcal conjugate vaccine (at 1 of 2 dosages) or the polysaccharide vaccine, with 2 doses given 2 months apart.

MAIN OUTCOME MEASUREMENTS

Immune response to each vaccine dose as determined by measurement of serogroup-specific total antibodies by enzyme-linked immunosorbent assay (ELISA) and by assessment of serum bactericidal activity.

RESULTS

Both vaccines appeared to be safe, and nearly all children responded with greater than 4-fold increases in antibody levels. The 2 dosages of the conjugate vaccine induced similar antibody responses; therefore, the data for the 2 conjugate vaccine groups were combined. Following 2 doses, ELISA antibody levels against group C meningococcus were significantly higher in conjugate vaccine recipients than in polysaccharide vaccine recipients (16.66 microg/mL vs. 8.31 microgm/mL; P<.001), but antibody levels against group A were not significantly different 22.75 microg/mL vs 21.24 microg/mL; P=.70). The serum bactericidal assays showed striking differences between the conjugate and polysaccharide vaccine groups. Geometric mean serum bactericidal titers were significantly higher in conjugate vaccine recipients (755.6 vs 37.6 for group A, P<.001; 3197.9 vs 11.4 for group C, P<.001).

CONCLUSIONS

The immune response induced by this meningococcal oligosaccharide-protein conjugate vaccine was qualitatively different from that induced by the polysaccharide vaccine, and the antibodies it elicited provided greater functional activity.