Haemophilus influenzae type b vaccine formulation and risk of childhood leukaemia

Intranasal coinfection model allows for assessment of protein vaccines against nontypeable Haemophilus influenzae in mice

PURPOSE

Nontypeable Haemophilus influenzae (NTHi) is a commensal in the human nasopharynx and the cause of pneumonia, meningitis, sinusitis, acute exacerbations of chronic obstructive pulmonary disease and acute otitis media (AOM). AOM is the most common ailment for which antibiotics are prescribed in the United States. With the emergence of new strains of antibiotic-resistant bacteria, finding an effective and broad coverage vaccine to protect against AOM-causing pathogens has become a priority. Mouse models are a cost-effective and efficient way to help determine vaccine efficacy. Here, we describe an NTHi AOM model in C57BL/6J mice, which also utilizes a mouse-adapted H1N1 influenza virus to mimic human coinfection.

METHODOLOGY

We tested our coinfection model using a protein vaccine formulation containing protein D, a well-studied NTHi vaccine candidate that can be found in the 10-valent Streptococcus pneumoniae conjugate vaccine. We verified the usefulness of our mouse model by comparing bacterial loads in the nose and ear between protein D-vaccinated and control mice.

RESULTS

While there was no measurable difference in nasal bacterial loads, we did detect significant differences in the bacterial loads of ear washes and ear bullae between vaccinated and control mice.

CONCLUSION

The results from this study suggest that our NTHi AOM coinfection model is useful for assessing protein vaccines.

Associations between vaccination and childhood cancers in Texas regions

OBJECTIVES

To determine whether children born in Texas regions with higher vaccination coverage had reduced risk of childhood cancer.

STUDY DESIGN

The Texas Cancer Registry identified 2800 cases diagnosed from 1995 to 2006 who were (1) born in Texas and (2) diagnosed at ages 2 to 17 years. The state birth certificate data were used to identify 11 200 age- and sex-matched control subjects. A multilevel mixed-effects regression model compared vaccination rates among cases and control subjects at the public health region and county level.

RESULTS

Children born in counties with higher hepatitis B vaccine coverage had lower odds of all cancers combined (OR = 0.81, 95% CI: 0.67 to 0.98) and acute lymphoblastic leukemia (ALL) specifically (OR = 0.63, 95% CI: 0.46 to 0.88). A decreased odds for ALL also was associated at the county level with higher rates of the inactivated poliovirus vaccine (OR = 0.67, 95% CI: 0.49 to 0.92) and 4-3-1-3-3 vaccination series (OR = 0.62, 95% CI: 0.44 to 0.87). Children born in public health regions with higher coverage levels of the Haemophilus influenzae type b-conjugate vaccine had lower odds of ALL (OR: 0.58; 95% CI: 0.42 to 0.82).

CONCLUSIONS

Some common childhood vaccines appear to be protective against ALL at the population level.

Maternal sensitivity concerning aetiological research into childhood cancer: results of preliminary focus groups

We and others have postulated that modifications to epidemiological methods and tools could improve understanding of childhood cancer aetiology. We describe features of paediatric cancer that influence study design and data collection strategies, and examine determinants of the reproducibility and accuracy of mothers' responses to questionnaires, which are the primary source of risk factor information. Two focus group sessions with mothers of children with acute lymphoblastic leukaemia (ALL) and two with mothers of children with brain tumours were conducted to explore: the optimal time of day, method of administration, and location for the interview; the availability of alternative data sources; the interval between paediatric cancer diagnosis and epidemiological interview; and other features which may affect maternal interview responses. Mothers of children with both types of cancer preferred being interviewed at home during the evening and were willing to provide complete access to their offsprings' medical records. Emotional, socio-economic and perhaps cultural differences between the groups of mothers were exemplified by the willingness of mothers of children with ALL to participate in epidemiological interviews earlier in their child's treatment course and to provide greater access to maternal reproductive history records compared with mothers of children with brain tumours. Parental concerns about the difficult disease and treatment course of children with brain tumours were a key element in their decision to defer participating in epidemiological interviews for many months after their child's cancer diagnosis. We conclude that the focus group approach can contribute to a broad strategy for improving questionnaires and methods for conducting paediatric cancer epidemiological research.

Vaccination history and risk of childhood leukaemia

BACKGROUND

Previous studies on vaccination and childhood leukaemia generated inconsistent results.

METHODS

In the Northern California Childhood Leukaemia Study, a case-control study with incident cases and matched birth certificate controls, detailed written vaccination records were collected. A total of 323 cases aged 0-14 years at diagnosis and 409 controls were included in this analysis. All vaccinations were censored on the reference date (date of diagnosis for cases and the corresponding date for matched controls). Conditional logistic regression analysis was conducted, adjusting for potential confounding factors. A primary variable of interest is the number of administrations (doses) of various types of vaccines.

RESULTS

Vaccinations against diphtheria, pertussis, tetanus, poliomyelitis, measles, mumps, and rubella were not associated with the risk of leukaemia. The odds ratio for each dose of Haemophilus influenzae type b (Hib) vaccine was 0.81 (95% CI 0.68-0.96). Compared with children who received two or fewer doses of Hib vaccine, those who received three or more doses had a significantly reduced risk of childhood leukaemia (odds ratio = 0.55, 95% confidence interval 0.32-0.94). The number of doses of hepatitis B vaccine received was not associated with leukaemia risk.

CONCLUSIONS

Hib vaccination is associated with a reduced risk of childhood leukaemia. Future studies with detailed exposure assessment and large sample sizes are needed to further address the role of vaccinations in the etiology of childhood leukaemia.

Day care in infancy and risk of childhood acute lymphoblastic leukaemia: findings from UK case-control study

OBJECTIVE

To test the hypothesis that reduced exposure to common infections in the first year of life increases the risk of developing acute lymphoblastic leukaemia. Design and setting The United Kingdom childhood cancer study (UKCCS) is a large population based case-control study of childhood cancer across 10 regions of the UK.

PARTICIPANTS

6305 children (aged 2-14 years) without cancer; 3140 children with cancer (diagnosed 1991-6), of whom 1286 had acute lymphoblastic leukaemia (ALL).

MAIN OUTCOME MEASURE

Day care and social activity during the first year of life were used as proxies for potential exposure to infection in infancy.

RESULTS

Increasing levels of social activity were associated with consistent reductions in risk of ALL; a dose-response trend was seen. When children whose mothers reported no regular activity outside the family were used as the reference group, odds ratios for increasing levels of activity were 0.73 (95% confidence interval 0.62 to 0.87) for any social activity, 0.62 (0.51 to 0.75) for regular day care outside the home, and 0.48 (0.37 to 0.62) for formal day care (attendance at facility with at least four children at least twice a week) (P value for trend < 0.001). Although not as striking, results for non-ALL malignancies showed a similar pattern (P value for trend < 0.001). When children with non-ALL malignancies were taken as the reference group, a significant protective effect for ALL was seen only for formal day care (odds ratio = 0.69, 0.51 to 0.93; P = 0.02). Similar results were obtained for B cell precursor common ALL and other subgroups, as well as for cases diagnosed above and below age 5 years.

CONCLUSION

These results support the hypothesis that reduced exposure to infection in the first few months of life increases the risk of developing acute lymphoblastic leukaemia.

An infectious aetiology for childhood acute leukaemia: a review of the evidence

There are three current hypotheses concerning infectious mechanisms in the aetiology of childhood leukaemia: exposure in utero or around the time of birth, delayed exposure beyond the first year of life to common infections and unusual population mixing. No specific virus has been definitively linked with childhood leukaemia and there is no evidence to date of viral genomic inclusions within leukaemic cells. The case-control and cohort studies have revealed equivocal results. Maternal infection during pregnancy has been linked with increased risk whilst breast feeding and day care attendance in the first year of life appear to be protective. There is inconclusive evidence from studies on early childhood infectious exposures, vaccination and social mixing. Some supportive evidence for an infectious aetiology is provided by the findings of space-time clustering and seasonal variation. Spatial clustering suggests that higher incidence is confined to specific areas with increased levels of population mixing, particularly in previously isolated populations. Ecological studies have also shown excess incidence with higher population mixing. The marked childhood peak in resource-rich countries and an increased incidence of the childhood peak in acute lymphoblastic leukaemia (ALL) (occurring at ages 2-6 years predominantly with precursor B-cell ALL) is supportive of the concept that reduced early infection may play a role. Genetically determined individual response to infection may be critical in the proliferation of preleukaemic clones as evidenced by the human leucocyte antigen class II polymorphic variant association with precursor B-cell and T-cell ALL.