MMR Vaccination and Autism

Assessing the impact of the 2018 Changchun Changsheng vaccine incident on childhood vaccination in China

BACKGROUND

The 2018 Changchun Changsheng vaccine incident is an emergent public health event in China with reports of DTaP vaccines with compromised efficacy. This study aimed to estimate the impact of the vaccine incident on real-world vaccination behaviors in China.

METHODS

A cross-sectional survey was conducted in ten provinces in 2019. Vaccination records were collected from 5294 children aged 6-59 months, with information on 75,579 vaccine doses for seven National Immunization Program (NIP) vaccines and two non-NIP vaccines received from 2014 to 2019. Chi-square test, interrupted time series, and logistic regression were used to evaluate the impacts of vaccine incident on vaccination delay, measured as the proportion of delayed doses out of total doses in schedule.

RESULTS

Here we show significant increases in doses delayed ≤ 3 months (19.12% to 22.51%, p = 0.000) and > 3 months (7.17% to 11.82%, p = 0.000) for DTaP vaccine after the incident. By scaling nationally, there will be extra 2.1 million doses delayed ≤ 3 months and 2.8 million doses delayed > 3 months in the year following this incident. More guardians choose expensive private-market substitutes containing DTaP elements over government-funded DTaP vaccines. Controlling for socio-demographic factors, doses scheduled after the incident have higher odds of delays for DTaP vaccine (OR: 3.49, 95% CI: 3.08-3.96) and other NIP vaccines (OR: 2.76, 95% CI: 2.55-2.99), but not for non-NIP vaccines.

CONCLUSIONS

The observed delays in the incident-involved DTaP vaccine immunization reflect the negative effects of the vaccine incident on vaccination behaviors under the NIP. However, its effects seem minimal for non-NIP vaccines.

Secondary Risk Theory: Validation of a Novel Model of Protection Motivation

Protection motivation theory states individuals conduct threat and coping appraisals when deciding how to respond to perceived risks. However, that model does not adequately explain today's risk culture, where engaging in recommended behaviors may create a separate set of real or perceived secondary risks. We argue for and then demonstrate the need for a new model accounting for a secondary threat appraisal, which we call secondary risk theory. In an online experiment, 1,246 participants indicated their intention to take a vaccine after reading about the likelihood and severity of side effects. We manipulated likelihood and severity in a 2 × 2 between-subjects design and examined how well secondary risk theory predicts vaccination intention compared to protection motivation theory. Protection motivation theory performed better when the likelihood and severity of side effects were both low (R² = 0.30) versus high (R² = 0.15). In contrast, secondary risk theory performed similarly when the likelihood and severity of side effects were both low (R² = 0.42) or high (R² = 0.45). But the latter figure is a large improvement over protection motivation theory, suggesting the usefulness of secondary risk theory when individuals perceive a high secondary threat.

Assessment of a new instrument for detecting preventable adverse drug reactions

BACKGROUND

Pharmacovigilance centres (PVCs) in the World Health Organization (WHO) Programme for International Drug Monitoring have demonstrated their ability to detect preventable adverse drug reactions (ADRs) in their databases. In this field, there is no gold-standard method for detecting medication errors and evaluating ADR preventability. Therefore, we developed, from existing tools, a preventability assessment method: the 'P Method' (PM).

OBJECTIVE

To present the PM and to evaluate its inter-rater reliability.

METHODS

The PM includes 20 explicit criteria for assessing ADR preventability. This approach is based on identification of any potentially preventable risk factor that increases the likelihood of ADR occurrence. The outcome of the preventability assessment results in one of three possible scores: 'preventable', 'non-preventable' or 'not assessable'. The PM was tested in a multicentre study involving nine national PVCs. Two experienced reviewers at each participating PVC independently analysed the preventability of 183 ADRs, applying the PM.

RESULTS

The overall agreement between all reviewers for assessment of ADR preventability was 'fair', with a kappa value of 0.27 [95 % confidence interval (CI) 0.21-0.40]. The level of agreement between reviewer pairs ranged from 'slight', with a kappa value of 0.12 (95 % CI -0.03 to 0.27), to 'substantial', with a kappa value of 0.69 (95 % CI 0.48-0.89).

CONCLUSION

The analysis of the agreements and disagreements between reviewers highlighted where improvements might be made. Given that no standard assessment tool exists in the WHO Programme, the transparency of the assessment process in this method provides a substantial basis for further development and for support in signalling possible preventability.

Proposed toxic and hypoxic impairment of a brainstem locus in autism

Electrophysiological findings implicate site-specific impairment of the nucleus tractus solitarius (NTS) in autism. This invites hypothetical consideration of a large role for this small brainstem structure as the basis for seemingly disjointed behavioral and somatic features of autism. The NTS is the brain's point of entry for visceral afference, its relay for vagal reflexes, and its integration center for autonomic control of circulatory, immunological, gastrointestinal, and laryngeal function. The NTS facilitates normal cerebrovascular perfusion, and is the seminal point for an ascending noradrenergic system that modulates many complex behaviors. Microvascular configuration predisposes the NTS to focal hypoxia. A subregion--the "pNTS"--permits exposure to all blood-borne neurotoxins, including those that do not readily transit the blood-brain barrier. Impairment of acetylcholinesterase (mercury and cadmium cations, nitrates/nitrites, organophosphates, monosodium glutamate), competition for hemoglobin (carbon monoxide, nitrates/nitrites), and higher blood viscosity (net systemic oxidative stress) are suggested to potentiate microcirculatory insufficiency of the NTS, and thus autism.

Influencing factors in MMR immunisation decision making

Immunisation decision making is not a straightforward process for parents. Many factors influence parental decision making on whether they immunise their child with the measles, mumps and rubella (MMR) vaccine. The feasibility study described in this article provides insight into influencing factors associated with decisions regarding the immunisation of children by parents. The study findings suggest that the practice nurse is a credible source of information for parents seeking informed decision making. At a time when the incidence of measles and mumps is rising in the UK, the provision of appropriate information by the practice nurse has the potential to increase uptake of the MMR vaccine.

Use of population based background rates of disease to assess vaccine safety in childhood and mass immunisation in Denmark: nationwide population based cohort study

OBJECTIVES

To predict the number of selected outcomes temporally associated but not caused by vaccination, to aid causality assessment of adverse events arising after mass immunisation in a paediatric population.

DESIGN

Nationwide population based cohort study.

SETTING

Denmark.

PARTICIPANTS

All liveborn infants delivered after 1 January 1980. Study population was followed from date of birth until hospital admission for selected outcome diagnoses, death, first emigration, age 18 years, or 31 December 2009. The study population was subject to vaccines used in standard childhood immunisation in Denmark, with 82-93% vaccine coverage.

MAIN OUTCOME MEASURES

Incidence of acute infectious and post-infectious polyneuritis (Guillain-Barré syndrome), acute transverse myelitis, optic polyneuritis, facial nerve palsy, anaphylactic shock, seizure, multiple sclerosis, autoimmune thrombocytopenia, type 1 diabetes mellitus, juvenile and rheumatoid arthritis, narcolepsy, and death of unknown cause stratified by sex, age, and season. We predicted the number of events for a hypothetical vaccine cohort of 1,000,000 people for follow-up periods of up to 182 days.

RESULTS

The study included 2,300,227 liveborn infants, yielding 37,262,404 person years of follow-up; median follow-up was 16.8 person years. Incidence of outcome diagnoses spanned from 0.32 per 100,000 patient years for autoimmune thrombocytopenia to 189.82 per 100,000 patient years for seizure. Seasonal differences were most pronounced for anaphylactic shock, seizure, and multiple sclerosis. Even for rare outcomes, numerous events were predicted in the hypothetical vaccine cohort. We predicted that 20 cases of type 1 diabetes mellitus, 19 of juvenile or rheumatoid arthritis, eight of facial nerve palsy, and five of multiple sclerosis per 1,000,000 children would occur within 42 days after vaccination.

CONCLUSIONS

Incorporating exact background rates of disease based on age, sex, and seasonal distribution could strengthen vaccine safety assessment, and provides an evidence based focus for discussing the incremental risk of newly introduced vaccines.

Expanding the Grading of Recommendations Assessment, Development, and Evaluation (Ex-GRADE) for Evidence-Based Clinical Recommendations: Validation Study

Clinicians use general practice guidelines as a source of support for their intervention, but how much confidence should they place on these recommendations? How much confidence should patients place on these recommendations? Various instruments are available to assess the quality of evidence of research, such as the revised Wong scale (R-Wong) which examines the quality of research design, methodology and data analysis, and the revision of the assessment of multiple systematic reviews (R-AMSTAR), which examines the quality of systematic reviews.

The Grading of Recommendation Assessment, Development, and Evaluation (GRADE) Working Group developed an instrument called the GRADE system in order to grade the quality of the evidence in studies and to evaluate the strength of recommendation of the intervention that is proposed in the published article. The GRADE looks at four factors to determine the quality of the evidence: study design, study quality, consistency, and directness. After combining the four components and assessing the grade of the evidence, the strength of recommendation of the intervention is established. The GRADE, however, only makes a qualitative assessment of the evidence and does not generate quantifiable data.

In this study, we have quantified both the grading of the quality of evidence and also the strength of recommendation of the original GRADE, hence expanding the GRADE. This expansion of the GRADE (Ex-GRADE) permits the creation of a new instrument that can produce tangible data and possibly bridge the gap between evidence-based research and evidence-based clinical practice.

Multiple sclerosis incidence in the era of measles-mumps-rubella mass vaccinations

BACKGROUND

Viral childhood infections may be involved in the multiple sclerosis (MS) pathogenesis. Following national Swedish vaccination programs, measles sharply declined in the 1970s, and measles, mumps, and rubella were virtually eliminated in cohorts born from 1981.

OBJECTIVES

To examine whether the vaccination induced reduction in these infections influences the MS incidence. In addition, the public health aspect justified an early evaluation of beneficial as well as harmful effects of mass vaccinations.

MATERIALS AND METHODS

From an incidence material of 534 MS patients, born 1959-1990, we selected one unvaccinated cohort and four cohorts, each corresponding to a vaccination program (MS patients = 251).

RESULTS

With the ability to detect a decrease by 30-35%, and an increase by 37-48% in the MS incidence in the first three cohorts, we found no vaccination related MS incidence changes. The background MS incidence showed a significant gradual age dependent increase.

CONCLUSIONS

While the present follow-up provided limited power in the last cohort, there is no evidence as yet that the radical decline in three viral infections influenced the MS incidence. However, the increasing background MS incidence of unknown cause may have concealed a reduction in MS risk associated with mass vaccinations.

Childhood autism and associated comorbidities

Autism is a heterogeneous neurodevelopmental disorder with a variety of different etiologies, but with a heritability estimate of more than 90%. Although the strong correlation between autism and genetic factors has been long established, the exact genetic background of autism is still unclear. This review refers to all the genetic syndromes that have been described in children with pervasive developmental disorders (tuberous sclerosis, fragile X, Down, neurofibromatosis, Angelman, Prader-Willi, Gilles de la Tourette, Williams, etc.). Issues covered include prevalence and main characteristics of each syndrome, as well as the possible base of its association with autism in terms of contribution to the current knowledge on the etiology and genetic base of pervasive developmental disorders.

Autism and environmental influences: review and commentary

Progress has been slow in identifying pre- and post-natal environmental exposures that might trigger the features that characterize autism. During the past thirty years, research in the field of autism has been conducted in a setting in which diagnostic criteria for this condition have changed and broadened, and differences of opinion regarding diagnostic issues and diagnostic terminology continue. The documented prevalence of all forms of autism has increased steadily during this time, suggesting one or more environmental contributors. Not established, however, is whether an increasing incidence of autism is responsible for increasing prevalence. The increase in documented prevalence could result from expanding and changing case definitions and increased reporting due to increased awareness on the part of professionals who work with children and by the public. This review provides a background for the evolving story of autism and describes the research on the relation between autism and the environment, with a particular focus on some of the more recently proposed environmental triggers. Critical analysis of this body of scientific research in a historical framework helps to explain the often controversial nature of the proposed relations between autism and environmental factors, as well as to rationalize some of the pitfalls in research design and in the often questionable interpretation of data so obtained.

Data Mining in the US using the Vaccine Adverse Event Reporting System

The US Vaccine Adverse Event Reporting System (VAERS), which is charged with vigilance for detecting vaccine-related safety issues, faces an increasingly complex immunisation environment. Since 1990, steady increases in vaccine licensing and distribution have resulted in increasing numbers of reports to VAERS. Prominent features of current reports include more routine vaccine co-administration and frequent reports of new postvaccination clinical syndromes. Data-mining methods, based on disproportionality analyses, are one strategy being pursued by VAERS researchers to increase the utility of its complex database. The types of analyses used include proportional reporting ratios, association rule discovery, and various 'historic limits' methods that compare observed versus expected event counts. The use of such strategies in VAERS has been primarily supplemental and retrospective. Signals for inactivated influenza, typhoid and tetanus toxoid-containing vaccines have been successfully identified. Concerns flagged through data mining should always be subject to clinical case review as a first evaluation step. Persistent issues should be subject to formal hypothesis testing in large linked databases or other controlled-study settings. Automated data-mining techniques for prospective use are currently undergoing development and evaluation within VAERS. Their use (as one signal-detection tool among many) by trained medical evaluators who are aware of system limitations is one legitimate approach to improving the ability of VAERS to generate vaccine-safety hypotheses. Such approaches are needed as more new vaccines continue to be licensed.