Timely versus delayed early childhood vaccination and seizures

Association Between Aluminum Exposure From Vaccines Before Age 24 Months and Persistent Asthma at Age 24 to 59 Months

OBJECTIVE

To assess the association between cumulative aluminum exposure from vaccines before age 24 months and persistent asthma at age 24 to 59 months.

METHODS

A retrospective cohort study was conducted in the Vaccine Safety Datalink (VSD). Vaccination histories were used to calculate cumulative vaccine-associated aluminum in milligrams (mg). The persistent asthma definition required one inpatient or 2 outpatient asthma encounters, and ≥2 long-term asthma control medication dispenses. Cox proportional hazard models were used to evaluate the association between aluminum exposure and asthma incidence, stratified by eczema presence/absence. Adjusted hazard ratios (aHR) and 95% confidence intervals (CI) per 1 mg increase in aluminum exposure were calculated, adjusted for birth month/year, sex, race/ethnicity, VSD site, prematurity, medical complexity, food allergy, severe bronchiolitis, and health care utilization.

RESULTS

The cohort comprised 326,991 children, among whom 14,337 (4.4%) had eczema. For children with and without eczema, the mean (standard deviation [SD]) vaccine-associated aluminum exposure was 4.07 mg (SD 0.60) and 3.98 mg (SD 0.72), respectively. Among children with and without eczema, 6.0% and 2.1%, respectively, developed persistent asthma. Among children with eczema, vaccine-associated aluminum was positively associated with persistent asthma (aHR 1.26 per 1 mg increase in aluminum, 95% CI 1.07, 1.49); a positive association was also detected among children without eczema (aHR 1.19, 95% CI 1.14, 1.25).

CONCLUSION

In a large observational study, a positive association was found between vaccine-related aluminum exposure and persistent asthma. While recognizing the small effect sizes identified and the potential for residual confounding, additional investigation of this hypothesis appears warranted.

Vaccination and childhood epilepsies

INTRODUCTION

The evidence relating vaccination to febrile seizures and epilepsy is evaluated with an emphasis on febrile seizures (FS), Dravet syndrome (DS), West syndrome, and other developmental and epileptic encephalopathies.

METHODS

A systematic literature review using search words vaccination/immunization AND febrile seizures/epilepsy/Dravet/epileptic encephalopathy/developmental encephalopathy was performed. The role of vaccination as the cause/trigger/aggravation factor for FS or epilepsies and preventive measures were analyzed.

RESULTS

From 1428 results, 846 duplicates and 447 irrelevant articles were eliminated; 120 were analyzed.

CONCLUSIONS

There is no evidence that vaccinations cause epilepsy in healthy populations. Vaccinations do not cause epileptic encephalopathies but may be non-specific triggers to seizures in underlying structural or genetic etiologies. The first seizure in DS may be earlier in vaccinated versus non-vaccinated patients, but developmental outcome is similar in both groups. Children with a personal or family history of FS or epilepsy should receive all routine vaccinations. This recommendation includes DS. The known risks of the infectious diseases prevented by immunization are well established. Vaccination should be deferred in case of acute illness. Acellular pertussis DTaP (diphtheria-tetanus-pertussis) is recommended. The combination of certain vaccine types may increase the risk of febrile seizures however the public health benefit of separating immunizations has not been proven. Measles-containing vaccine should be administered at age 12-15 months. Routine prophylactic antipyretics are not indicated, as there is no evidence of decreased FS risk and they can attenuate the antibody response following vaccination. Prophylactic measures (preventive antipyretic medication) are recommended in DS due to the increased risk of prolonged seizures with fever.

Vaccination deferral among children with seizures in Zhejiang: influence, recommendation, safety and implications

OBJECTIVES

Delayed vaccination in children with seizures was common in China. This study aims to describe the vaccination status, reasons for vaccination deferral, vaccination recommendations and the safety for these patients in Zhejiang.

METHODS

1539 children included were divided into febrile seizure (FS) group, epilepsy (EP) group, unclassified seizure group and other symptomatic seizure group. Medical records and reasons for the vaccination deferral were collected by questionnaire. Vaccination data and Adverse Event Following Immunization were retrieved from vaccination booklets.

RESULTS

The main diseases of children enrolled were FS (756, 49.1%) and EP (443, 28.8%). Most of them (95.6%) were vaccinated on time before the onset of seizure, but their vaccination was delayed after seizure occurred. 76.1% were recommended to receive vaccines normally, of which the FS group accounted for the highest proportion (90.3%). 88.73% of them were vaccinated as recommended, and no serious side effects or seizure occurred. The main reason for vaccination deferral was providers' and parents' hesitation to have them vaccinated.

CONCLUSION

Seizures were overestimated as a contraindication for vaccination in China. Routine vaccination was safe in most circumstances. It is essential to educate providers and parents about the benefits and contraindications of vaccination in children with seizures.

Safety of vaccines used for routine immunization in the United States: An updated systematic review and meta-analysis

BACKGROUND

Understanding the safety of vaccines is critical to inform decisions about vaccination. Our objective was to conduct a systematic review of the safety of vaccines recommended for children, adults, and pregnant women in the United States.

METHODS

We searched the literature in November 2020 to update a 2014 Agency for Healthcare Research and Quality review by integrating newly available data. Studies of vaccines that used a comparator and reported the presence or absence of key adverse events were eligible. Adhering to Evidence-based Practice Center methodology, we assessed the strength of evidence (SoE) for all evidence statements. The systematic review is registered in PROSPERO (CRD42020180089).

RESULTS

Of 56,603 reviewed citations, 338 studies reported in 518 publications met inclusion criteria. For children, SoE was high for no increased risk of autism following measles, mumps, and rubella (MMR) vaccine. SoE was high for increased risk of febrile seizures with MMR. There was no evidence of increased risk of  intussusception with rotavirus vaccine at the latest follow-up (moderate SoE), nor of diabetes (high SoE). There was no evidence of increased risk or insufficient evidence for key adverse events for newer vaccines such as 9-valent human papillomavirus and meningococcal B vaccines. For adults, there was no evidence of increased risk (varied SoE) or insufficient evidence for key adverse events for the new adjuvanted inactivated influenza vaccine and recombinant adjuvanted zoster vaccine. We found no evidence of increased risk (varied SoE) for key adverse events among pregnant women following tetanus, diphtheria, and acellular pertussis vaccine, including stillbirth (moderate SoE).

CONCLUSIONS

Across a large body of research we found few associations of vaccines and serious key adverse events; however, rare events are challenging to study. Any adverse events should be weighed against the protective benefits that vaccines provide.

Immunogenicity and Safety of an Early Measles Vaccination Schedule at 6 and 12 Months of Age in Human Immunodeficiency Virus (HIV)-Unexposed and HIV-Exposed, Uninfected South African Children

BACKGROUND

Measles morbidity and mortality rates are greatest in children <12 months old, with increased susceptibility in human immunodeficiency virus (HIV)-exposed children. We evaluated the immunogenicity and safety of an early 2-dose measles vaccine regimen administered at 6 and 12 months of age in South Africa.

METHODS

HIV-unexposed (HU) (n = 212) and HIV-exposed, uninfected (HEU) (n = 71) children received measles vaccination (CAM-70) at 6 and 12 months of age. Measles immunoglobulin G titers were measured by means of enzyme-linked immunosorbent assay before and 1 month after each vaccine dose.

RESULTS

The majority of children (88.2% HU and 95.8% HEU; P = .04) were seronegative (<150 mIU/mL) to measles at 4.2 months of age. This was particularly evident among infants of mothers born from 1992 onwards (year of public nationwide measles vaccine availability). One month after the first measles vaccine, 42.3% of HU and 46.4% of HEU children were seropositive (≥330 mIU/mL). After the second dose, the proportion seropositive increased to 99.0% in HU and 95.3% in HEU children. Safety profiles were similar between HU and HEU children.

CONCLUSIONS

Early 2-dose measles vaccination at 6 and 12 months of age was safe and induced antibody responses in HU and HEU children, which could partly offset the early loss of maternally derived antibodies in infants born to predominantly measles-vaccinated mothers.

CLINICAL TRIALS REGISTRATION

NCT03330171.

Vaccine safety in infants and children

Immunization is crucial to maintaining public health. This article addresses the benefits of childhood vaccinations and educates parents on the myths surrounding possible adverse reactions.

Similar relative risks of seizures following measles containing vaccination in children born preterm compared to full-term without previous seizures or seizure-related disorders

BACKGROUND

Febrile seizures are associated with the first dose of measles-containing vaccines and the risk increases with chronologic age during the second year of life. We used the Vaccine Safety Datalink (VSD) to determine if the relative increase in risk of seizures following receipt of measles-containing vaccine differs by gestational age at birth.

METHODS

Children were eligible if they received their first dose of measles-containing vaccine at age 12 through 23 months from January 2003 through September 2015. Children were excluded if they had a history of seizure or conditions strongly related to seizure prior to 12 months of age. Seizures were identified by diagnostic codes in the inpatient or emergency department settings. Using risk-interval analysis, we estimated the incidence rate ratio (IRR) for seizures in the 7 through 10 days (risk period) vs 15 through 42 days (control period) following receipt of measles-containing vaccines in children born preterm (<37 weeks gestation age) and those born full-term (≥37 weeks).

RESULTS

There were 532,375 children (45,343 preterm and 487,032 full-term) who received their first dose of measles-containing vaccine at age 12 through 23 months. The IRRs of febrile seizures 7 through 10 days compared with 15 through 42 days after receipt of measles-containing vaccine were 3.9 (95% CI: 2.5-6.0) in preterm children and 3.2 (2.7-3.7) in full-term children; the ratio of IRRs: was 1.2 (0.76-1.9), p = 0.41. IRRs were also similar across gestational age groups, by vaccine type received (measles-mumps-rubella [MMR] or measles-mumps-rubella-varicella [MMRV]) and age at vaccination (12-15 or 16-23 months).

CONCLUSION

Vaccination with a measles-containing vaccine in the second year of life is associated with a similar relative risk of a first seizure in children born preterm as in those who were born full-term.

Spontanuous Demand For Meningococcal B Vaccination: Effects On Appropriateness And Timing

When the meningococcus B vaccine was introduced into Italy in 2017, it was recommended for newborns based on national epidemiological data indicating that they were at greater risk. However, the vaccination service of the local health authority of L'Aquila had already been receiving spontaneous parental requests to provide vaccination for children in lower-risk age groups from the beginning of 2016. We therefore decided to use a self-administered questionnaire in order to investigate the parents’ socio-demographic data; their children's history of other recommended vaccinations (against measles, mumps and rubella, varicella, meningococcus C and, for females, human papilloma virus); the information sources concerning meningococcal vaccination; and the timing of its administration.

The questionnaire was completed by 565 parents, and the results showed that the requests mainly came from the parents of children aged 5–11 years. The children whose mothers had received a high school education and were >35 years old were more likely to have received the first dose after the age of one year and to have perceived pain at the inoculation site, and less likely to have experienced mild general reactions. The requests were mainly trigged by the recommendations of healthcare professionals, and the overloading of the vaccination service led to delays in the administration of the doses after the first. The delays (reported by 74.07% of the parents) were mainly due to organisational problems in the service itself, which led 61.52% of the doses being more appropriately administered by staff working as private physicians inside public health facilities, albeit at extra cost.

These findings indicate that organisational factors and excessive demand had a considerable impact on both the efficacy of the immunisation and its appropriateness.

Post-immunisation fever and the antibody response to measles-containing vaccines

Fever is a common adverse event following measles vaccination, more frequent among older children and those receiving Measles-Mumps-Rubella-Varicella vaccine vs. Measles-Mumps-Rubella vaccine, two factors associated with a better antibody response. However, the role of fever in the immunogenicity of measles-containing vaccines (MCV) is unclear. We performed a post-hoc pooled analysis of data of 5 216 11 to 22 month-old children receiving MCV from 2004 to 2012 in Europe and USA to evaluate the association between post-immunisation fever and antibody response, measured by geometric mean concentrations (GMCs). We further evaluated fever as an effect modifier or a mediator in the associations between the type of MCV or the age at first vaccination and vaccine immunogenicity. After the first dose, fever was associated with 60% higher GMCs (95% CI 1.51–1.68). For children vaccinated at ⩾12 months, the fever did not modify and minimally mediated (2% to 3%) the association between age and antibody response. Fever mediated 18% of the association between type of MCV and GMCs. In a model including fever, age and type of vaccine, fever was the strongest predictor of GMCs. These results suggest that fever is associated with a stronger measles antibody response independently of age and type of MCV.

Analyzing self-controlled case series data when case confirmation rates are estimated from an internal validation sample

Vaccine safety studies are often electronic health record (EHR)-based observational studies. These studies often face significant methodological challenges, including confounding and misclassification of adverse event. Vaccine safety researchers use self-controlled case series (SCCS) study design to handle confounding effect and employ medical chart review to ascertain cases that are identified using EHR data. However, for common adverse events, limited resources often make it impossible to adjudicate all adverse events observed in electronic data. In this paper, we considered four approaches for analyzing SCCS data with confirmation rates estimated from an internal validation sample: (1) observed cases, (2) confirmed cases only, (3) known confirmation rate, and (4) multiple imputation (MI). We conducted a simulation study to evaluate these four approaches using type I error rates, percent bias, and empirical power. Our simulation results suggest that when misclassification of adverse events is present, approaches such as observed cases, confirmed case only, and known confirmation rate may inflate the type I error, yield biased point estimates, and affect statistical power. The multiple imputation approach considers the uncertainty of estimated confirmation rates from an internal validation sample, yields a proper type I error rate, largely unbiased point estimate, proper variance estimate, and statistical power.

Methods for addressing "innocent bystanders" when evaluating safety of concomitant vaccines

PURPOSE

The need to develop methods for studying the safety of childhood immunization schedules has been recognized by the Institute of Medicine and Department of Health and Human Services. The recommended childhood immunization schedule includes multiple vaccines in a visit. A key concern is safety of concomitant (same day) versus separate day vaccination. This paper addresses a methodological challenge for observational studies using a self-controlled design to investigate the safety of concomitant vaccination.

METHODS

We propose a process for distinguishing which of several concomitantly administered vaccines is responsible for increased risk of an adverse event while adjusting for confounding due to relationships between effect modifying risk factors and concomitant vaccine combinations. We illustrate the approach by re-examining the known increase in risk of seizure 7 to 10 days after measles-mumps-rubella (MMR) vaccination and evaluating potential independent or modifying effects of other vaccines.

RESULTS

Initial analyses suggested that DTaP had both an independent and potentiating effect on seizure. After accounting for the relationship between age at vaccination and vaccine combination, there was little evidence for increased risk of seizure with same day administration of DTaP and MMR; incidence rate ratio, 95% confidence interval 1.2 (0.9-1.6), P value = θ.226.

CONCLUSION

We have shown that when using a self-controlled design to investigate safety of concomitant vaccination, it can be critically important to adjust for time-invariant effect modifying risk factors, such as age at time of vaccination, which are structurally related to vaccination patterns due to recommended immunization schedules.

Immunization Coverage in Migrant School Children Along the Thailand-Myanmar Border

The objective of this project was to document and increase vaccine coverage in migrant school children on the Thailand-Myanmar border. Migrant school children (n = 12,277) were enrolled in a school-based immunization program in four Thai border districts. The children were evaluated for vaccination completion and timing, for six different vaccines: Bacille Calmette-Guerin (BCG); Oral Polio vaccine (OPV); Hepatitis B vaccine (HepB); Diphtheria, Pertussis and Tetanus vaccine (DTP); Measles Containing Vaccine or Measles, Mumps and Rubella vaccine (MMR); Tetanus and Diphtheria containing vaccine (Td). Vaccine coverage proportions for BCG, OPV3, DTP3, HepB3 and measles containing vaccine were 92.3, 85.3, 63.8, 72.2, and 90.9 % respectively. Most children were able to receive vaccines in a time appropriate manner. School-based immunization programs offer a suitable vaccine delivery mechanism for hard-to-reach populations. However, these data suggest overall low vaccine coverage in migrant populations. Further efforts toward improving appropriate vaccine coverage and methods of retaining documentation of vaccination in mobile migrant populations are necessary for improved health.

The Influence of Vaccine on Febrile Seizure

BACKGROUND

The protective value of vaccines to the public has made vaccines among the major public health prophylactic measures through the entire history. However, there has been some controversy about their safety; particularly concerns have been rising about febrile seizures (FS). Vaccination was found to be the second most common cause of FS.

METHODS

We research and collect relative online content for reviewing the effects of vaccine in FS.

RESULTS

there is no causal relationship between FS and vaccination. This relationship is complex by other factors, such as age, genetic inheritance, type of vaccine, combination of different types of vaccines and the timing of vaccination.

CONCLUSION

In order to reduce FS after vaccination, it is important to understand the mechanism of epilepsy and relationship between specific vaccines and FS. Parents should be informed that some vaccines could be associated with an increased risk of FS, particularly, in children with personal and family history of FS. Children with genetic epilepsy syndrome are prone to seizures and certain vaccinations should be avoided in these children. It is highly recommended to choose vaccines with lower risk of developing FS and to administer these vaccines during the low risk window of immunizations schedule.

Timeliness of childhood vaccination in the Federated States of Micronesia

BACKGROUND

Vaccination coverage is typically measured as the proportion of individuals who have received recommended vaccine doses by the date of assessment. This approach does not provide information about receipt of vaccines by the recommended age, which is critical for ensuring optimal protection from vaccine-preventable diseases (VPDs).

OBJECTIVE

To assess vaccination timeliness in the Federated States of Micronesia (FSM), and the projected impact of suboptimal vaccination in the event of an outbreak.

METHODS

Timeliness of the 4th dose of diphtheria, tetanus, and acellular pertussis vaccine (DTaP) and 1st dose of measles, mumps, and rubella vaccine (MMR) among children 24-35 months was assessed in FSM. Both doses are defined as on time if administered from 361 through 395 days in age. Timeliness was calculated by one-way frequency analysis, and dose delays, measured in months after recommended age, were described using inverse Kaplan-Meier analysis. A time-series susceptible-exposed-infected-recovery (TSEIR) model simulated measles outbreaks in populations with on time and late vaccination.

RESULTS

Total coverage for the 4th dose of DTaP ranged from 36.6% to 98.8%, and for the 1st dose of MMR ranged from 80.9% to 100.0% across FSM states. On time coverage for the 4th dose of DTaP ranged from 3.2% to 52.3%, and for the 1st dose of MMR ranged from 21.1% to 66.9%. Maximum and median dose delays beyond the recommended age varied by state. TSEIR models predicted 10.8-13.7% increases in measles cases during an outbreak based on these delays.

CONCLUSIONS

In each of the FSM states, a substantial proportion of children received DTaP and MMR doses outside the recommended timeframe. Children who receive vaccinations later than recommended remain susceptible to VPDs during the period they remain unvaccinated, which may have a substantial impact on health systems during an outbreak. Immunization programs should consider vaccination timeliness in addition to coverage as a measure of susceptibility to VPDs in young children.

Evaluation of Combination Measles-Mumps-Rubella-Varicella Vaccine Introduction in Australia

IMPORTANCE

Incorporating combination vaccines, such as the measles-mumps-rubella-varicella (MMRV) vaccine, into immunization schedules should be evaluated from a benefit-risk perspective. Use of MMRV vaccine poses challenges due to a recognized increased risk of febrile seizures (FSs) when used as the first dose in the second year of life. Conversely, completion by age 2 years of measles, mumps, rubella, and varicella immunization may offer improved disease control.

OBJECTIVE

To evaluate the effect on safety and coverage of earlier (age 18 months) scheduling of MMRV vaccine as the second dose of measles-containing vaccine (MCV) in Australia.

DESIGN, SETTING, AND PARTICIPANTS

Prospective active sentinel safety surveillance comparing the relative incidence (RI) of FSs in toddlers given MMRV and measles-mumps-rubella (MMR) and a national cohort study of vaccine coverage rates and timeliness before and after MMRV vaccine introduction were conducted. All Australian children aged 11 to 72 months were included in the coverage analysis, and 1471 Australian children aged 11 to 59 months were included in the FS analysis, with a focus on those aged 11 to 23 months.

MAIN OUTCOMES AND MEASURES

MMRV vaccine safety, specifically, the RI of FSs after MMRV vaccine at age 18 months, compared with risk following MMR vaccine and vaccine uptake for 2-dose MCV and single-dose varicella vaccine, focusing on timeliness.

RESULTS

Of the 1471 children, the median age at first FS was 21 months (interquartile range [IQR], 14-31 months). Three hundred ninety-one children were aged 11 to 23 months and had at least 1 FS included in the analysis; of these, 207 (52.9%) were male. A total of 278 children (71.1%) had received MMR followed by MMRV vaccine, 97 (24.8%) had received MMR vaccine only, and 16 (4.1%) had received neither vaccine. There was no increased risk of FSs (RI, 1.08; 95% CI, 0.55-2.13) in the 5 to 12 days following MMRV vaccine given as the second MCV to toddlers. Febrile seizures occurred after dose 1 of MMR vaccine at a known low increased risk (RI, 2.71; 95% CI, 1.71- 4.29). Following program implementation, 2-dose MCV coverage at age 36 months exceeded that obtained at age 60 months in historical cohorts recommended to receive MMR vaccine before school entry, and on-time vaccination increased by 13.5% (from 58.9% to 72.4%). Despite no change in the scheduled age of varicella vaccine, use of MMRV vaccine was associated with a 4.0% increase in 1-dose varicella vaccine coverage.

CONCLUSIONS AND RELEVANCE

To our knowledge, this is the first study to provide evidence of the absence of an association between use of MMRV vaccine as the second dose of MCV in toddlers and an increased risk of FSs. Incorporation of MMRV vaccine has facilitated improvements in vaccine coverage that will potentially improve disease control.

MMR and MMRV vaccines

Measles, mumps, rubella and varicella are viral infections which can implicate seriously long-term sequelae of infected individuals or even the unborn child. Vaccines against the individual diseases have long been available. Global measles vaccination is estimated to have prevented more than 20million deaths during 2000-2015. During the same time period, measles incidence decreased from 146 to 36 cases per million populations. Today vaccinations against measles, mumps, rubella and varicella are now carried out mainly with combination vaccines. These are today known as immunogenic and safe. MMRV had similar immunogenicity and overall safety profiles to MMR administered with or without varicella vaccine. This issue provides a review of the different vaccines, mode of administration, catch up immunization and postexposure prophylaxis as well as contraindications and adverse effects of the immunization against measles, mumps, rubella, and varicella. The article presents an overview of important information of preventing these diseases with a focus on the existing combination vaccines.

Immunological considerations regarding parental concerns on pediatric immunizations

Despite the fundamental role of vaccines in the decline of infant mortality, parents may decide to decline vaccination for their own children. Many factors may influence this decision, such as the belief that the infant immune system is weakened by vaccines, and concerns have been raised about the number of vaccines and the early age at which they are administered. Studies focused on the infant immune system and its reaction to immunizations, summarized in this review, show that vaccines can overcome those suboptimal features of infant immune system that render them more at risk of infections and of their severe manifestations. In addition, many vaccines have been shown to improve heterologous innate and adaptive immunity resulting in lower mortality rates for fully vaccinated children. Thus, multiple vaccinations are necessary and not dangerous, as infants can respond to several antigens as well as when responding to single stimuli. Current immunization schedules have been developed and tested to avoid vaccine interference, improve benefits and reduce side effects compared to single administrations. The infant immune system is therefore capable, early after birth, of managing several antigenic challenges and exploits them to prompt its development.

Employment and Socioeconomic Factors Associated With Children's Up-to-Date Vaccination Status

This study examined whether additional information on parents' employment and household characteristics would help explain the differences in children's up-to-date (UTD) vaccination status using the 2008 National Immunization Survey and its associated Socioeconomic Status Module. After controlling for basic sociodemographic factors in multivariable analyses, parent's work schedules and ease of taking time off from work were not associated with UTD vaccination status among 19- to 35-month-old children. We also conducted a stratified analysis to test the heterogeneous effects of the factors among children at 3 age-restricted maternal education levels and found the benefit of paid sick leave had a significant association only among families where the mother had a college degree. Families who had moved since the child's birth, especially if the mother had high school or lower education, were less likely to have children UTD on the vaccine series.

Risk factors and familial clustering for fever 7-10days after the first dose of measles vaccines

BACKGROUND

Seven to ten days after a first dose of a measles-containing vaccine (MCV; i.e., MMR or MMRV), children have elevated fever risk which can be associated with febrile seizures. This study investigated individual and familial factors associated with fever 7-10days after MCV.

METHODS

Retrospective cohort study among children who were <36months of age at receipt of MCV in six sites of the Vaccine Safety Datalink from 1/1/2000 to 12/31/2012. We evaluated medically-attended clinic or emergency department visits with a code for fever 7-10days after any MCV ("MCV- associated"). We evaluated factors associated with MCV-associated fever using χ² and multivariable logistic regression analyses.

RESULTS

Among 946,806 children vaccinated with MCV, we identified 7480 (0.8%) MCV-associated fever visits. Compared with children without fever after MCV, children with MCV-associated fever were more likely to have received MMRV than MMR (OR 1.3 95% CI 1.2, 1.5), have had medically attended fever both following previous vaccines (OR 1.3 95% CI 1.1, 1.6) and at any other previous time (OR 1.7 95% CI 1.6, 1.8), have had at least 1 prior seizure (OR 2.2 95% CI 1.7, 2.7), and have had >3 medical visits within the 6months before MCV (OR 1.7 95% CI 1.6, 1.8). In families with multiple MCV-immunized children, after adjusting for healthcare seeking behavior care for fever, those whose siblings had MCV-associated fever were more likely to also have MCV-associated fever (OR 3.5 95% CI 2.5, 4.8).

DISCUSSION

Children who received MMRV vaccine or who had prior medically-attended fevers and seizures during the first year of life had increased risk of fever after a first dose of measles vaccine. After adjusting for familial propensity to seek care, MCV-associated fever still clustered within families, suggesting a possible genetic basis for susceptibility to developing fever due to measles vaccines.

Vaccine adverse events in a safety net healthcare system and a managed care organization

BACKGROUND

The Institute of Medicine, in a 2013 report, recommended that the Vaccine Safety Datalink (VSD) expand collaborations to include more diversity in the study population. Kaiser Permanente Colorado (KPCO), an established VSD site, partnered with Denver Health (DH), an integrated safety net healthcare system, to demonstrate the feasibility of integrating DH data within the VSD. Prior to incorporating the data, we examined the identification of specific vaccine associated adverse events (VAEs) in these two distinct healthcare systems.

METHODS

We conducted retrospective cohort analyses within KPCO and DH to compare select VAEs between the two populations. We examined the following associations between January 1, 2004 and December 31, 2013: Measles, Mumps, and Rubella (MMR) vaccine and febrile seizures in children 2years and younger, intussusception after rotavirus vaccine in infants 4-34weeks, syncope after adolescent vaccines (Tetanus, Diphtheria, acellular Pertussis; Meningococcal and Human Papillomavirus) in adolescents 13-17years and medically attended local reactions after pneumococcal polysaccharide (PPSV23) vaccine in adults 65years and older. Both sites used similar data procurement methods and chart review processes.

RESULTS

For seizures after MMR vaccine (KPCO - 3.15vs. DH - 2.97/10,000 doses) and syncope after all adolescent vaccines (KPCO - 3.0vs. DH - 2.37/10,000 doses), the chart confirmed rates were comparable at the two sites. However, for medically attended local reactions after PPSV23, there were differences in chart confirmed rates between the sites (KPCO - 31.65vs. DH - 14.90/10,000 doses). For intussusception after rotavirus vaccine, the number of cases was too low to make a valid comparison (KPCO - 0vs. DH - 0.13/10,000 doses).

CONCLUSION

We demonstrated that data on important targeted VAEs can be captured at DH and rates appear similar to those at KPCO. Work is ongoing on the optimal approach to assimilate DH data as a potential safety net healthcare system in the VSD.

An observational study of febrile seizures: the importance of viral infection and immunization

Background

Febrile seizures are common in young children. Annual peaks in incidence mirror increased respiratory virus activity during winter. Limited virological data are available using modern diagnostic techniques for children with febrile seizures. We aimed to determine the frequency of detection of specific viral pathogens in children with febrile seizures, to describe risk factors including recent vaccination and clinical features associated with specific etiologies.

Methods

An observational study was performed. Children aged 6 months to 5 years presenting to the Emergency Department of a tertiary children’s hospital in Western Australia with febrile seizures were enrolled between March 2012 and October 2013. Demographic, clinical data and vaccination history were collected, and virological testing was performed on per-nasal and per-rectal samples.

Results

One hundred fifty one patients (72 female; median age 1.7y; range 6 m-4y9m) were enrolled. Virological testing was completed for 143/151 (95%). At least one virus was detected in 102/143 patients (71%). The most commonly identified were rhinoviruses (31/143, 22%), adenovirus (30/151, 21%), enteroviruses, (28/143, 20%), influenza (19/143, 13%) and HHV6 (17/143, 12%). More than one virus was found in 48/143 (34%). No significant clinical differences were observed when children with a pathogen identified were compared with those with no pathogen detected. Febrile seizures occurred within 14 days of vaccine administration in 16/151 (11%).

Conclusion

At least one virus was detected in over two thirds of cases tested (commonly picornaviruses, adenovirus and influenza). Viral co-infections were frequently identified. Febrile seizures occurred infrequently following immunization.

HOW DO WE EVALUATE AND MANAGE MANY DIFFERENT VACCINATION SCHEDULES IN THE EU?

BACKGROUND

Vaccines are biologic medical products, the biological activity and characteristics of which are significantly different from common drugs and other medical products. The process of determining the dosing (vaccination) schedule for a particular vaccine is based on different principles and rules than other drugs. The dosing schedule for drugs is based on the essential pharmacological properties: pharmacokinetics and pharmacodynamics. When determining the schedule for vaccines, the pharmacokinetic and pharmacodynamic principles cannot be applied: sero-conversion and sero-protectivity of the biologically active component of the vaccine need to be applied. As opposed to drugs and medical products the dosing (vaccination) schedule in the Summary of Product Characteristics (SPC) is often provided in several versions, sometimes with a supplement referring to official (national) recommendations. In relation to the large variability vaccination schedules in the European Union (EU), it is not realistic to test each vaccination schedule in clinical studies. Requiring clinical trials for each vaccination schedule used only for the needs of regulators is more of an ethical issue than a scientific one. The European Centre for Disease Prevention and Control (ECDC), which is the Scientific Panel on Childhood Immunisation Schedule (SPACIS), accepts all the schedules used in EU countries as valid.

METHODS AND RESULTS

A review of the literature on immunisation schedules for primary series and booster doses choosing the following key words: immunisation, vaccination schedule, primary, booster, timing, vaccination delay.

Monitoring of timely and delayed vaccinations: a nation-wide registry-based study of Norwegian children aged < 2 years

BACKGROUND

Delayed vaccinations increase the risk for vaccine preventable diseases (VPDs). Monitoring of delayed vaccinations by using a national immunisation registry has not been studied in countries recommending a two-dose (3 and 5 months of age) primary series of e.g., pertussis vaccine. Surveillance/monitoring of all vaccinations may improve vaccination programmes functioning.

METHODS

We obtained information from the Norwegian immunisation registry (SYSVAK) on all programme vaccinations received at age up to 730 days in children born in 2010 (n = 63,382). Timely vaccinations were received up to 7 days after the recommended age. Vaccinations were considered delayed if they were received more than one month after the recommended age in the schedule.

RESULTS

In vaccinated children, timely administration of the subsequent three doses of pertussis and one dose of measles occurred in 73.8, 47.6, 53.6 and 43.5 % respectively. Delay for one or more programme vaccinations (diphtheria, tetanus, pertussis, polio, Haemophilus influenza type B, invasive pneumococcal disease, measles, mumps or rubella) was present in 28,336 (44.7 %) children. Among those who were delayed the mean duration was 139 days. The proportion of children that had vaccinations delayed differed among counties (range 37.4 %-57.8 %). Immigrant children were more frequently delayed 52.3 % vs. 43.1 %, RR 1.21 (95 % CI 1.19, 1.24). Children scheduled for vaccines in the summer holiday month (July) were more frequently delayed than others (1(st) dose pertussis vaccine 6.5 % vs. 3.9 % RR 1.65 (95 % CI 1.48, 1.85). Priming against pertussis (2(nd) dose), pneumococcal (2(nd) dose) and measles (1(st) dose) was delayed in 16.8, 18.6 and 29.3 % respectively.

CONCLUSION

Vaccinations were frequently delayed. Delayed vaccinations differed among counties and occurred more frequently during the summer vacation (July) and in the immigrant population. Monitoring improves programme surveillance and may be used on an annual basis.

Risk Communication, Values Clarification, and Vaccination Decisions

Many health-related decisions require choosing between two options, each with risks and benefits. When presented with such tradeoffs, people often make choices that fail to align with scientific evidence or with their own values. This study tested whether risk communication and values clarification methods could help parents and guardians make evidence-based, values-congruent decisions about children's influenza vaccinations. In 2013-2014 we conducted an online 2×2 factorial experiment in which a diverse sample of U.S. parents and guardians (n = 407) were randomly assigned to view either standard information about influenza vaccines or risk communication using absolute and incremental risk formats. Participants were then either presented or not presented with an interactive values clarification interface with constrained sliders and dynamic visual feedback. Participants randomized to the risk communication condition combined with the values clarification interface were more likely to indicate intentions to vaccinate (β = 2.10, t(399) = 2.63, p < 0.01). The effect was particularly notable among participants who had previously demonstrated less interest in having their children vaccinated against influenza (β = -2.14, t(399) = -2.06, p < 0.05). When assessing vaccination status reported by participants who agreed to participate in a follow-up study six months later (n = 116), vaccination intentions significantly predicted vaccination status (OR = 1.66, 95%CI (1.13, 2.44), p < 0.05) and rates of informed choice (OR = 1.51, 95%CI (1.07, 2.13), p < 0.012), although there were no direct effects of experimental factors on vaccination rates. Qualitative analysis suggested that logistical barriers impeded immunization rates. Risk communication and values clarification methods may contribute to increased vaccination intentions, which may, in turn, predict vaccination status if logistical barriers are also addressed.

Vaccination uptake by vaccine-hesitant parents attending a specialist immunization clinic in Australia

Vaccine hesitancy (VH) is an issue of global concern. The quality of communication between healthcare providers and parents can influence parental immunization acceptance. We aimed to describe immunization uptake following specialist immunization clinic (SIC) consultation for Australian children of VH parents as a cohort, and according to pre-clinic parental position on immunization. At a single tertiary pediatric SIC (RCH, Melbourne) a retrospective descriptive study classified VH families according to 3 proposed parental positions on immunization at initial clinic attendance. Immunization status at follow up was ascertained via the Australian Children's Immunization Register and National HPV Program Register and compared between groups. Of the VH cohort, 13/38 (34%) families were classified as hesitant, 21 (55%) as late/selective vaccinators and 4 (11%) as vaccine refusers. Mean follow up post-SIC attendance was 14.5 months. For the overall VH cohort, the majority chose selective immunization (42%) following SIC consultation. When analyzed by pre-clinic parental position on immunization, there was a trend for hesitant families to proceed with full immunization, selective families to continue selective immunization and refusing families to remain unimmunised (p < 0.0001). The most commonly omitted vaccines were hepatitis B (66%) and Haemophilus influenzae type B (55%), followed by the meningococcal C conjugate vaccine (53%) and measles, mumps and rubella vaccine (53%). Immunization outcome appears to correlate with pre-clinic parental position on immunization for the majority of families attending a SIC in Australia, with selective immunization the most common outcome. Tailored communication approaches based on parental position on immunization may optimise clinic resources and engagement of families, but require prospective research evaluation.

Risk factors for delay in age-appropriate vaccinations among Gambian children

BACKGROUND

Vaccination has been shown to reduce mortality and morbidity due to vaccine-preventable diseases. However, these diseases are still responsible for majority of childhood deaths worldwide especially in the developing countries. This may be due to low vaccine coverage or delay in receipt of age-appropriate vaccines. We studied the timeliness of routine vaccinations among children aged 12-59 months attending infant welfare clinics in semi-urban areas of The Gambia, a country with high vaccine coverage.

METHODS

A cross-sectional survey was conducted in four health centres in the Western Region of the Gambia. Vaccination dates were obtained from health cards and timeliness assessed based on the recommended age ranges for BCG (birth-8 weeks), Diphtheria-Pertussis-Tetanus (6 weeks-4 months; 10 weeks-5 months; 14 weeks-6 months) and measles vaccines (38 weeks-12 months). Risk factors for delay in age-appropriate vaccinations were determined using logistic regression. Analysis was limited to BCG, third dose of Diphtheria-Pertussis -Tetanus (DPT3) and measles vaccines.

RESULTS

Vaccination records of 1154 children were studied. Overall, 63.3% (95 % CI 60.6-66.1%) of the children had a delay in the recommended time to receiving at least one of the studied vaccines. The proportion of children with delayed vaccinations increased from BCG [5.8% (95 % CI 4.5-7.0%)] to DPT3 [60.4% (95 % CI 57.9%-63.0%)] but was comparatively low for the measles vaccine [10.8% (95 % CI 9.1%-12.5%)]. Mothers of affected children gave reasons for the delay, and their profile correlated with type of occupation, place of birth and mode of transportation to the health facilities.

CONCLUSION

Despite high vaccination coverage reported in The Gambia, a significant proportion of the children's vaccines were delayed for reasons related to health services as well as profile of mothers. These findings are likely to obtain in several countries and should be addressed by programme managers in order to improve and optimize the impact of the immunization coverage rates.

Effect of vaccinations on seizure risk and disease course in Dravet syndrome

OBJECTIVE

To study the effect of vaccination-associated seizure onset on disease course and estimate the risk of subsequent seizures after infant pertussis combination and measles, mumps, and rubella (MMR) vaccinations in Dravet syndrome (DS).

METHODS

We retrospectively analyzed data from hospital medical files, child health clinics, and the vaccination register for children with DS and pathogenic SCN1A mutations. Seizures within 24 hours after infant whole-cell, acellular, or nonpertussis combination vaccination or within 5 to 12 days after MMR vaccination were defined as "vaccination-associated." Risks of vaccination-associated seizures for the different vaccines were analyzed in univariable and in multivariable logistic regression for pertussis combination vaccines and by a self-controlled case series analysis using parental seizure registries for MMR vaccines. Disease courses of children with and without vaccination-associated seizure onset were compared.

RESULTS

Children who had DS (n = 77) with and without vaccination-associated seizure onset (21% and 79%, respectively) differed in age at first seizure (median 3.7 vs 6.1 months, p < 0.001) but not in age at first nonvaccination-associated seizure, age at first report of developmental delay, or cognitive outcome. The risk of subsequent vaccination-associated seizures was significantly lower for acellular pertussis (9%; odds ratio 0.18, 95% confidence interval [CI] 0.05-0.71) and nonpertussis (8%; odds ratio 0.11, 95% CI 0.02-0.59) than whole-cell pertussis (37%; reference) vaccines. Self-controlled case series analysis showed an increased incidence rate ratio of seizures of 2.3 (95% CI 1.5-3.4) within the risk period of 5 to 12 days following MMR vaccination.

CONCLUSIONS

Our results suggest that vaccination-associated earlier seizure onset does not alter disease course in DS, while the risk of subsequent vaccination-associated seizures is probably vaccine-specific.

Three randomized trials of maternal influenza immunization in Mali, Nepal, and South Africa: Methods and expectations

Influenza infection in pregnancy can have adverse impacts on maternal, fetal, and infant outcomes. Influenza vaccination in pregnancy is an appealing strategy to protect pregnant women and their infants. The Bill & Melinda Gates Foundation is supporting three large, randomized trials in Nepal, Mali, and South Africa evaluating the efficacy and safety of maternal immunization to prevent influenza disease in pregnant women and their infants <6 months of age. Results from these individual studies are expected in 2014 and 2015. While the results from the three maternal immunization trials are likely to strengthen the evidence base regarding the impact of influenza immunization in pregnancy, expectations for these results should be realistic. For example, evidence from previous influenza vaccine studies - conducted in general, non-pregnant populations - suggests substantial geographic and year-to-year variability in influenza incidence and vaccine efficacy/effectiveness. Since the evidence generated from the three maternal influenza immunization trials will be complementary, in this paper we present a side-by-side description of the three studies as well as the similarities and differences between these trials in terms of study location, design, outcome evaluation, and laboratory and epidemiological methods. We also describe the likely remaining knowledge gap after the results from these trials become available along with a description of the analyses that will be conducted when the results from these individual data are pooled. Moreover, we highlight that additional research on logistics of seasonal influenza vaccine supply, surveillance and strain matching, and optimal delivery strategies for pregnant women will be important for informing global policy related to maternal influenza immunization.

Risk of febrile seizure after measles-mumps-rubella-varicella vaccine: A systematic review and meta-analysis

BACKGROUND

Considering the febrile seizure rate, there is no longer a clear preference for use of measles-mumps-rubella-varicella (MMRV) vaccine over separate measles-mumps-rubella (MMR) and varicella (V) vaccine. This work was undertaken to assess the risk of febrile seizure after MMRV vaccine in children.

METHODS

We searched PubMed, Embase, BIOSIS Previews, Scopus, Web of Science, Cochrane Library and other databases through 12 December 2014. Meta-analysis was conducted using R version 3.1.2 and Stata version 12.0.

RESULTS

A total of thirty-nine studies were included. Thirty-one published or unpublished clinical trials involving about 40,000 subjects did not show significant differences in incidence of febrile seizure or vaccine related febrile seizure between MMRV and MMR with or without varicella vaccine after any doses, in the risk windows of 0-28, 0-42 or 0-56 days and 7-10 days. In addition, these studies showed that the receipt of concomitant use of MMRV and other pediatric vaccines was not a significant predictor of febrile seizure. Eight post-marketing observations involving more than 3,200,000 subjects were included. No evidence suggested elevated risk of febrile seizure associated with MMRV vaccine among children aged 4-6 years old during 7-10 days or 0-42 days after vaccination. However, an approximately 2-fold increase in risk of seizure or febrile seizure during 7-10 days or 5-12 days after MMRV vaccination was found among children aged 10-24 months, although the highest incidence of seizure was still lower than 2.95‰.

CONCLUSIONS

First MMRV vaccine dose in children aged 10-24 months was associated with an elevated risk of seizure or febrile seizure. Further post-marketing restudies based on more rigorous study design are needed to confirm the findings.

Spatial patterns of epilepsy-related emergency department visits in california

Background

Socio-demographic factors are associated with increased emergency department (ED) use among patients with epilepsy. However, there has been limited spatial analysis of such visits.

Design and methods

California ED visit at the patient ZIP Code level were examined using Kulldorf’s spatial scan statistic to identify clusters of increased risk for epilepsy-related visits. Logistic regression was used to examine the relative importance of patient socio-demographics, Census-based and hospital measures.

Results

During 2009-2011 there were 29,715,009 ED visits at 330 hospitals, of which 139,235 (0.5%) had epilepsy (International Classification of Disease-9 345.xx) as the primary diagnosis. Three large urban clusters of high epilepsy-related ED visits were centred in the cities of Los Angeles, Oakland and Stockton and a large rural cluster centred in Kern County. No consistent pattern by age, race/ethnicity, household structure, and income was observed among all clusters. Regression found only the Los Angeles cluster significant after adjusting for other measures.

Conclusions

Geospatial analysis within a large and geographically diverse region identified a cluster within its most populous city having an increased risk of ED visits for epilepsy independent of selected socio-demographic and hospital measures. Additional research is necessary to determine whether elevated rates of ED visits represent increased prevalence of epilepsy or an inequitable system of epilepsy care.

Physician response to parental requests to spread out the recommended vaccine schedule

OBJECTIVES

To assess among US physicians (1) frequency of requests to spread out recommended vaccination schedule for children <2 years, (2) attitudes regarding such requests, and (3) strategies used and perceived effectiveness in response to such requests.

METHODS

An e-mail and mail survey of a nationally representative sample of pediatricians and family physicians from June 2012 through October 2012.

RESULTS

The response rate was 66% (534 of 815). In a typical month, 93% reported some parents of children <2 years requested to spread out vaccines; 21% reported ≥ 10% of parents made this request. Most respondents thought these parents were putting their children at risk for disease (87%) and that it was more painful for children (84%), but if they agreed to requests, it would build trust with families (82%); further, they believed that if they did not agree, families might leave their practice (80%). Forty percent reported this issue had decreased their job satisfaction. Most agreed to spread out vaccines when requested, either often/always (37%) or sometimes (37%); 2% would often/always, 4% would sometimes, and 12% would rarely dismiss families from their practice if they wanted to spread out the primary series. Physicians reported using a variety of strategies in response to requests but did not think they were effective.

CONCLUSIONS

Virtually all providers encounter requests to spread out vaccines in a typical month and, despite concerns, most are agreeing to do so. Providers are using many strategies in response but think few are effective. Evidence-based interventions to increase timely immunization are needed to guide primary care and public health practice.

Safety of measles-containing vaccines in 1-year-old children

BACKGROUND AND OBJECTIVES

All measles-containing vaccines are associated with several types of adverse events, including seizure, fever, and immune thrombocytopenia purpura (ITP). Because the measles-mumps-rubella-varicella (MMRV) vaccine compared with the separate measles-mumps-rubella (MMR) and varicella (MMR + V) vaccine increases a toddler's risk for febrile seizures, we investigated whether MMRV is riskier than MMR + V and whether either vaccine elevates the risk for additional safety outcomes.

METHODS

Study children were aged 12 to 23 months in the Vaccine Safety Datalink from 2000 to 2012. Nine study outcomes were investigated: 7 main outcomes (anaphylaxis, ITP, ataxia, arthritis, meningitis/encephalitis, acute disseminated encephalomyelitis, and Kawasaki disease), seizure, and fever. Comparing MMRV with MMR + V, relative risk was estimated by using stratified exact binomial tests. Secondary analyses examined post-MMRV or MMR + V risk versus comparison intervals; risk and comparison intervals were then contrasted for MMRV versus MMR+V.

RESULTS

We evaluated 123,200 MMRV and 584,987 MMR + V doses. Comparing MMRV with MMR + V, risks for the 7 main outcomes were not significantly different. Several outcomes had few or zero postvaccination events. Comparing risk versus comparison intervals, ITP risk was higher after MMRV (odds ratio [OR]: 11.3 [95% confidence interval (CI): 1.9 to 68.2]) and MMR + V (OR: 10 [95% CI: 4.5 to 22.5]) and ataxia risk was lower after both vaccines (MMRV OR: 0.8 [95% CI: 0.5 to 1]; MMR + V OR: 0.8 [95% CI: 0.7 to 0.9]). Compared with MMR + V, MMRV increased risk of seizure and fever 7 to 10 days after vaccination.

CONCLUSIONS

This study did not identify any new safety concerns comparing MMRV with MMR + V or after either the MMRV or the MMR + V vaccine. This study provides reassurance that these outcomes are unlikely after either vaccine.

The Vaccine Safety Datalink: successes and challenges monitoring vaccine safety

The Vaccine Safety Datalink (VSD) is a collaborative project between the Centers for Disease Control and Prevention (CDC) and 9 health care organizations. Established in 1990, VSD is a vital resource informing policy makers and the public about the safety of vaccines used in the United States. Large linked databases are used to identify and evaluate adverse events in over 9 million individuals annually. VSD generates rapid, important safety assessments for both routine vaccinations and emergency vaccination campaigns. VSD monitors safety of seasonal influenza vaccines in near-real time, and provided essential information on the safety of influenza A (H1N1) 2009 monovalent vaccine during the recent pandemic. VSD investigators have published important studies demonstrating that childhood vaccines are not associated with autism or other developmental disabilities. VSD prioritizes evaluation of new vaccines; searches for possible unusual health events after vaccination; monitors vaccine safety in pregnant women; and has pioneered development of biostatistical research methods.