Age distribution of infection and hospitalization among Canadian First Nations populations during the 2009 H1N1 pandemic

Influenza-associated hospitalisation and mortality rates among global Indigenous populations; a systematic review and meta-analysis

BACKGROUND

More than 50 million influenza infections and over 100,000 deaths from influenza occur annually. While Indigenous populations experience an inequitable influenza burden, the magnitude of this inequity has not previously been estimated on a global scale. This study compared rates of influenza-associated hospitalisation and mortality between Indigenous and non-Indigenous populations globally.

METHODS

A systematic review and meta-analysis was conducted including literature published prior to 13 July 2021. Eligible articles either reported a rate ratio (RR) comparing laboratory-confirmed influenza-associated hospitalisation and/or mortality between an Indigenous population and a corresponding benchmark population, or reported sufficient information for this to be calculated using publicly available data. Findings were reported by country/region and pooled by country and period (pandemic/seasonal) when multiple studies were available using a random-effects model. The I2 statistic assessed variability between studies.

RESULTS

Thirty-six studies (moderate/high quality) were included; all from high or high-middle income countries. The pooled influenza-associated hospitalisation RR (HRR) for indigenous compared to benchmark populations was 5·7 (95% CI: 2·7-12·0) for Canada, 5·2 (2.9-9.3) for New Zealand, and 5.2 (4.2-6.4) for Australia. Of the Australian studies, the pooled HRR for seasonal influenza was 3.1 (2·7-3·5) and for pandemic influenza was 6·2 (5·1-7·5). Heterogeneity was slightly higher among studies of pandemic influenza than seasonal influenza. The pooled mortality RR was 4.1 (3·0-5.7) in Australia and 3·3 (2.7-4.1) in the United States.

CONCLUSIONS

Ethnic inequities in severe influenza persist and must be addressed by reducing disparities in the underlying determinants of health. Influenza surveillance systems worldwide should include Indigenous status to determine the extent of the disease burden among Indigenous populations. Ethnic inequities in pandemic influenza illustrate the need to prioritise Indigenous populations in pandemic response plans.

Acute health care among Indigenous patients in Canada: a scoping review

A recent report by the Chief Public Health Officer of Canada demonstrates the inferior health status of Indigenous Peoples in Canada when compared to non-Indigenous populations. This scoping review maps out the available literature concerning acute health care for Indigenous Peoples in Canada in order to better understand the health care issues they face. All existing articles concerning health care provided to Indigenous Peoples in Canada in acute settings were included in this review. The targeted studied outcomes were access to care, health care satisfaction, hospital visit rates, mortality, quality of care, length of stay and cost per hospitalisation. 114 articles were identified. The most studied outcomes were hospitalisation rates (58.8%), length of stay (28.0%), mortality (25.4%) and quality of care (24.6%) Frequently studied topics included pulmonary disease, injuries, cardiovascular disease and mental illness. Indigenous Peoples presented lower levels of satisfaction and access to care although they tend to be over-represented in hospitalisation rates for acute care. Greater inclusion of Indigenous Peoples in the health care system and in the training of health care providers is necessary to ensure a better quality of care that is culturally safe for Indigenous Peoples.

Risk factors and mitigation of influenza among Indigenous children in Australia, Canada, United States, and New Zealand: a scoping review

AIM

This review considers prominent risk factors and mitigation strategies of influenza among Indigenous children.

METHODS

Seven electronic databases were searched from the period of 2004-2017 to locate articles discussing influenza among Indigenous children in the developed circumpolar nations of Australia, Canada, United States, and New Zealand. Articles selected for inclusion discussed influenza among Indigenous children as either individuals or as a part of a community. Ancestry searches of articles meeting the review criteria were also undertaken to discern seminal research in this topic area.

RESULTS

From the 39 primary research studies included, marked risk factors and mitigation strategies of influenza among Indigenous children were identified using inductive analysis. Notable risk factors included age under 2 years, cigarette smoke exposure, presence of a chronic illness, and crowded living conditions. Successful mitigation of influenza for Indigenous children included strategies to improve vaccine coverage, provision of health education, and policy change.

CONCLUSION

In the past, the impact of influenza upon Indigenous communities has been devastating for both children and their families. By utilizing existing public health infrastructure and collaborating with culturally unique Indigenous groups, preventive action for Indigenous children at significant risk of contracting influenza can be realized.

Review of seasonal influenza in Canada: Burden of disease and the cost-effectiveness of quadrivalent inactivated influenza vaccines

In the 2015/16 influenza season, the Canadian National Advisory Committee on Immunization (NACI) recommended vaccination with quadrivalent inactivated influenza vaccine (QIV) for infants aged 6-23 months and trivalent inactivated influenza vaccines (TIVs) or QIVs in adults. The objective of this review (GSK study identifier: HO-13-14054) is to examine the epidemiology and disease burden of influenza in Canada and the economic benefits of vaccination. To inform this review, we performed a systematic literature search of relevant Canadian literature and National surveillance data. Influenza B viruses from phylogenetically-distinct lineages (B/Yamagata and B/Victoria) co-circulate in Canada, and are an important cause of influenza complications. Modeling studies, including those postdating the search suggest that switching from TIV to QIV in Canada reduces the burden of influenza and would likely be cost-effective. However, more robust real-world outcomes data is required to inform health policy decision makers on appropriate influenza vaccination strategies for Canada.

Effectiveness of the 2013 and 2014 Southern Hemisphere Influenza Vaccines Against Laboratory-confirmed Influenza in Young Children Using a Test-negative Design, Bangkok, Thailand

BACKGROUND

The Thai Advisory Committee on Immunization Practices recommends annual influenza vaccination for children 6 months through 2 years of age, although older children may be vaccinated on request. We evaluated the effectiveness of the 2013 and 2014 inactivated influenza vaccines to reduce medically attended, laboratory-confirmed influenza illness among Thai children aged 7-60 months.

METHODS

From September 2013-May 2015, children with influenza-like illness were screened with a rapid influenza diagnostic test. Enrolled children had nasal and throat swabs tested for influenza viruses using polymerase chain reaction. Cases and controls were subjects testing positive and negative, respectively, for influenza viruses by polymerase chain reaction. Vaccination status was ascertained from vaccination cards. Vaccine effectiveness (VE) was calculated as 100% × (1 - odds ratio of vaccination among cases vs. controls).

RESULTS

Of the 1377 children enrolled, cases (n = 490) and controls (n = 887) were similar in demographic characteristics. Cases were less likely to receive influenza vaccine than controls in 2013 (6% vs. 14%; P = 0.02), but not in 2014 (6% vs. 7%; P = 0.57). Among cases, 126 (26%) were positive for influenza A(H1N1)pdm09 virus, 239 (49%) for influenza A(H3N2) and 124 (25%) for influenza B. One specimen was positive for both influenza A(H3N2) and B viruses. VE for full vaccination against all viruses was 64% (95% confidence interval: 21% to 84%) in 2013 and 26% (95% confidence interval: -47% to 63%) in 2014.

CONCLUSIONS

Influenza vaccination was low among Thai children in this study, and VE varied by year, highlighting the need for annual monitoring of VE to better understand vaccine program effectiveness.

Modelling the impact of vaccination on curtailing Haemophilus influenzae serotype 'a'

Haemophilus influenzae serotype a (Hia) is a human-restricted bacterial pathogen transmitted via direct contacts with an infectious individual. Currently, there is no vaccine available for prevention of Hia, and the disease is treated with antibiotics upon diagnosis. With ongoing efforts for the development of an anti-Hia protein-polysaccharide conjugated vaccine, we sought to investigate the effect of vaccination on curtailing Hia infection. We present the first stochastic model of Hia transmission and control dynamics, and parameterize it using available estimates in the literature. Since both naturally acquired and vaccine-induced immunity wane with time, model simulations show three important results. First, vaccination of only newborns cannot eliminate the pathogen from the population, even when a booster program is implemented with a high coverage. Second, achieving and maintaining a sufficiently high level of herd immunity for pathogen elimination requires vaccination of susceptible individuals in addition to a high vaccination coverage of newborns. Third, for a low vaccination rate of susceptible individuals, a high coverage of booster dose may be needed to raise the level of herd immunity for Hia eradication. Our findings highlight the importance of vaccination and timely boosting of the individual׳s immunity within the expected duration of vaccine-induced protection against Hia. When an anti-Hia vaccine becomes available, enhanced surveillance of Hia incidence and herd immunity could help determine vaccination rates and timelines for booster doses necessary to eliminate Hia from affected populations.

The impact of ethnicity and geographical location of residence on the 2009 influenza H1N1 pandemic vaccination

In Canada, vaccination policies against the 2009 influenza H1N1 pandemic (H1N1pdm09) were modified at different times during the autumn wave. We hypothesized that ethnicity and place of residence influenced the odds of vaccination. To test this hypothesis, we used vaccination databases for the entire province of Manitoba, and obtained the age distribution of vaccination for First Nations (FN) and non-First Nations (non-FN) populations. We used regression analysis to determine the effect of ethnicity and location of residence on odds of vaccination. We found that individuals with FN identity were over 2.8 times [95% confidence interval (CI) 2.79-2.87] more likely to receive vaccination compared to non-FN individuals. For the FN populations, on-reserve residency was associated with 5.15-fold (95% CI 5.00-5.30) higher odds of vaccination compared to off-reserve residency. Our study highlights the importance of demographic and geographical variables in developing strategies for vaccine prioritization.

An outbreak of influenza A (H1N1) virus in a remote Aboriginal community post-pandemic: implications for pandemic planning and health service policy

OBJECTIVE

To describe a 2013 outbreak of pandemic influenza A (H1N1) virus in a remote Western Australian Aboriginal community; inform outbreak prevention and control measures and discuss the community susceptibility to H1N1, three years after the A(H1N1)pdm09 pandemic.

METHODS

Records at the local clinic were used to classify cases as 'confirmed' (laboratory test positive for H1N1 or temperature >38°C with cough and/or sore throat) or 'probable' (self-reported fever with cough and/or sore throat). Additional data were collected from medical records and public health databases.

RESULTS

A total of 108 individuals met case definitions. Clinical attack rate was 23%. Children under five years of age had the highest age-specific attack rate (545 per 1,000 population). Thirty cases (28%) experienced complications with six (5.6%) requiring aero-evacuation. Only 7% of the community had received H1N1-containing vaccine during the previous year. No H1N1 cases from the community were previously reported.

CONCLUSIONS

This is the first description of the effects of a novel influenza strain on a remote Australian Aboriginal community. Isolation and low vaccination are likely explanations for the apparent naivety to H1N1.

IMPLICATIONS

There may be other remote communities at risk of H1N1. High attack and complication rates confirm that Aboriginal Australians should be prioritised in pandemic planning.

Antiviral strategies for emerging influenza viruses in remote communities

BACKGROUND

Due to the lack of timely access to resources for critical care, strategic use of antiviral drugs is crucial for mitigating the impact of novel influenza viruses with pandemic potential in remote and isolated communities. We sought to evaluate the effect of antiviral treatment and prophylaxis of close contacts in a Canadian remote northern community.

METHODS

We used an agent-based, discrete-time simulation model for disease spread in a remote community, which was developed as an in-silico population using population census data. Relative and cumulative age-specific attack rates, and the total number of infections in simulated model scenarios were obtained.

RESULTS

We found that early initiation of antiviral treatment is more critical for lowering attack rates in a remote setting with a low population-average age compared to an urban population. Our results show that a significant reduction in the relative, age-specific attack rates due to increasing treatment coverage does not necessarily translate to a significant reduction in the overall arrack rate. When treatment coverage varies from low to moderate, targeted prophylaxis has a very limited impact in reducing attack rates and should be offered at a low level (below 10%) to avoid excessive waste of drugs.

CONCLUSIONS

In contrast to previous work, for conservative treatment coverages, our results do not provide any convincing evidence for the implementation of targeted prophylaxis. The findings suggest that public health strategies in remote communities should focus on the wider availability (higher coverage) and timely distribution of antiviral drugs for treatment of clinically ill individuals.

The impact of geographical location of residence on disease outcomes among Canadian First Nations populations during the 2009 influenza A(H1N1) pandemic

We sought to evaluate the effect of geographical location of residence on disease burden in Canadian First Nations (FN) populations during the 2009 pandemic influenza A(H1N1). Descriptive statistics and regression analysis of data for cases of pandemic A(H1N1) infection and hospitalization in the province of Manitoba, Canada, were conducted to estimate the odds of hospitalization and delay in time-to-hospitalization for on-reserve and off-reserve FN populations, while considering their geographical proximity to urban centers. We found that on-reserve FN individuals experienced a longer delay between infection and hospitalization compared to off-reserve FN individuals (p<0.001). The average fraction of FN cases that experienced a delay longer than 4 days for hospitalization was 20% higher for on-reserve compared to off-reserve residence. The odds of hospitalization were twice as high for FN people living on-reserve as compared to off-reserve (odds ratio=2.34; 95% CI: 1.16-4.73). Given the independent effect of on-reserve residency, higher disease burden among FN people cannot be attributed entirely to limited healthcare access due to remoteness from urban centers.

Influenza H3N2 variant viruses with pandemic potential: preventing catastrophe in remote and isolated Canadian communities

OBJECTIVE

To evaluate the impact of age-specific cross-reactive antibody protection levels on the outcomes of a pandemic outbreak of new variants of H3N2 influenza A viruses (H3N2v).

METHODS

We calibrated a previously validated agent-based model of human-to-human transmission of influenza viruses to project the outcomes of various protection levels in a remote and isolated Canadian community, when demographics are drawn from the Statistics Canada census data. We then compared the outcomes with a scenario in which demographic variables were shifted to resemble an urban structure. This comparative evaluation was conducted using in-silico computer simulations, where the epidemiological data were drawn from relevant estimates in published literature.

RESULTS

Simulations, using estimates of transmissibility for the 2009 H1N1 pandemic strain in the study population, show that the epidemic size is primarily affected by the cross-reactive protection levels of young children. A lower number of secondary infections at the early stages of an outbreak does not necessarily correspond to a lower epidemic size.

CONCLUSIONS

Demographic variables could play a significant role in determining the outcomes of an outbreak. The findings strongly suggest that, when an H3N2v-specific vaccine becomes available, children below the age of 17 should be prioritized for vaccination. This prioritization is essential in population settings with a low average age, including aboriginal communities in northern latitudes.

Research priorities in modeling the transmission risks of H7N9 bird flu

The epidemic of H7N9 bird flu in eastern China in early 2013 has caused much attention from researchers as well as public health workers. The issue on modeling the transmission risks is very interesting topic. In this article, this issue is debated and discussed in order to promote further researches on prediction and prevention of avian influenza viruses supported by better interdisciplinary datasets from the surveillance and response system.

Indigenous populations health protection: a Canadian perspective

The disproportionate effects of the 2009 H1N1 pandemic on many Canadian Aboriginal communities have drawn attention to the vulnerability of these communities in terms of health outcomes in the face of emerging and reemerging infectious diseases. Exploring the particular challenges facing these communities is essential to improving public health planning. In alignment with the objectives of the Pandemic Influenza Outbreak Research Modelling (Pan-InfORM) team, a Canadian public health workshop was held at the Centre for Disease Modelling (CDM) to: (i) evaluate post-pandemic research findings; (ii) identify existing gaps in knowledge that have yet to be addressed through ongoing research and collaborative activities; and (iii) build upon existing partnerships within the research community to forge new collaborative links with Aboriginal health organizations. The workshop achieved its objectives in identifying main research findings and emerging information post pandemic, and highlighting key challenges that pose significant impediments to the health protection and promotion of Canadian Aboriginal populations. The health challenges faced by Canadian indigenous populations are unique and complex, and can only be addressed through active engagement with affected communities. The academic research community will need to develop a new interdisciplinary framework, building upon concepts from 'Communities of Practice', to ensure that the research priorities are identified and targeted, and the outcomes are translated into the context of community health to improve policy and practice.