Natality Decline and Spatial Variation in Excess Death Rates During the 1918-1920 Influenza Pandemic in Arizona, United States

Comparative analysis of COVID-19 diagnoses and mortality among hospitalized indigenous and non-indigenous populations in Chile: 2020-2021

BACKGROUND

Current literature presents mixed effects of the COVID-19 pandemic on Indigenous communities. We aim to highlight potential disparities and temporal shifts in both the impact of COVID-19 and vaccine uptake among hospitalized Indigenous populations in Chile.

METHODS

We conducted an observational analysis utilizing 1,598,492 hospitalization records from 2020 to 2021 based on publicly accessible hospital discharge data spanning 65 healthcare facilities of medium and high complexity funded through the Diagnosis-Related Groups (DRG) mechanism in Chile, representing roughly 70% of the country's total hospitalizations. This was supplemented with publicly available municipal data on COVID-19 vaccinations and socio-demographic variables. We performed logistic regression analysis at 0.05 level of significance to assess the bivariate and multivariable association of Indigenous status with COVID-19 diagnosis and COVID-19 deaths among hospitalized populations. We also performed univariate and multiple linear regression to assess the association of COVID-19 vaccination rate and Indigenous status at the municipality level. In addition, we report the distribution of top 10 secondary diagnoses among hospitalized COVID-19 cases and deaths separately for Indigenous and non-Indigenous populations.

RESULTS

Indigenous populations displayed lower adjusted odds for both COVID-19 diagnosis (OR: 0.76, 95% CI: 0.74, 0.77) and death (OR: 0.91, 95% CI: 0.85, 0.97) when compared to non-Indigenous groups. Notably, the adjusted odds ratio for COVID-19 diagnosis in Indigenous populations rose from 0.59 (95% CI: 0.57, 0.61) in 2020 to 1.17 (95% CI: 1.13, 1.21) in 2021. Factors such as the significantly higher median age and greater number of comorbidities in the non-Indigenous hospitalized groups could account for their increased odds of COVID-19 diagnosis and mortality. Additionally, our data indicates a significantly negative adjusted association between COVID-19 vaccination rates and the proportion of Indigenous individuals.

CONCLUSION

Although Indigenous populations initially showed lower odds of COVID-19 diagnosis and mortality, a marked rise in diagnosis odds among these groups in 2021 underscores the urgency of targeted interventions. The observed negative association between the proportion of Indigenous populations and vaccination rates further underscores the necessity to tackle vaccine access barriers and work towards equitable distribution.

Did the 1918 influenza pandemic cause a 1920 baby boom? Demographic evidence from neutral Europe

In 1919-20, the European countries that were neutral in the First World War saw a small baby bust followed by a small baby boom. The sparse literature on this topic attributes the 1919 bust to individuals postponing conceptions during the peak of the 1918-20 influenza pandemic and the 1920 boom to recuperation of those conceptions. Using data from six large neutral countries of Europe, we present novel evidence contradicting that narrative. In fact, the subnational populations and maternal birth cohorts whose fertility was initially hit hardest by the pandemic were still experiencing below-average fertility in 1920. Demographic evidence, economic evidence, and a review of post-pandemic fertility trends outside Europe suggest that the 1920 baby boom in neutral Europe was caused by the end of the First World War, not by the end of the pandemic.

What can we learn from historical pandemics? A systematic review of the literature

What are the insights from historical pandemics for policymaking today? We carry out a systematic review of the literature on the impact of pandemics that occurred since the Industrial Revolution and prior to Covid-19. Our literature searches were conducted between June 2020 and September 2023, with the final review encompassing 169 research papers selected for their relevance to understanding either the demographic or economic impact of pandemics. We include literature from across disciplines to maximise our knowledge base, finding many relevant articles in journals which would not normally be on the radar of social scientists. Our review identifies two gaps in the literature: (1) the need to study pandemics and their effects more collectively rather than looking at them in isolation; and (2) the need for more study of pandemics besides 1918 Spanish Influenza, especially milder pandemic episodes. These gaps are a consequence of academics working in silos, failing to draw on the skills and knowledge offered by other disciplines. Synthesising existing knowledge on pandemics in one place provides a basis upon which to identify the lessons in preparing for future catastrophic disease events.

Human fertility after a disaster: a systematic literature review

Fertility is a key demographic parameter influenced by disaster. With the growing risk of disasters, interest in the fertility response to a disaster is increasing among the public, policy makers and researchers alike. However, a systematic literature review on how disaster affects live birth counts does not yet exist. We reviewed 50 studies retrieved from a systematic search based on a pre-registered protocol. We found an overall negative impact of disasters on fertility. If any, increases in fertility were mostly linked with weather-related physical disasters. We also identified 13 distinct mechanisms which researchers have considered as underlying the fertility effects of disaster. By contrast to the common belief that disasters are more likely to increase fertility in contexts with already high fertility, we found little evidence to suggest that the total fertility rate of the studied populations was an important predictor of the direction, timing or size of fertility impacts. While this may be because no relationship exists, it may also be due to biases we observed in the literature towards studying high-income countries or high-cost disasters. We summarize the methodological limitations identified from the reviewed studies into six practical recommendations for future research. Our findings inform both the theories behind the fertility effects of disasters and the methods for studying them.

Tropism and Infectivity of Pandemic Influenza A H1N1/09 Virus in the Human Placenta

Influenza virus infection in pregnant women may put the fetus at higher risk; however, to date, there has been no detailed research about the expression of influenza virus receptors in the human placenta. We employed the lectin staining technique, which is a classic influenza virus receptor research method for studying the distribution of viral receptors in the human placenta. In addition, we examined the susceptibility of the human placenta to H1N1/09, by detecting viral proteins and RNA at different time points post-infection. We found that the human placenta expressed both avian and human influenza A virus receptors (α-2, 3-linked sialic acid and α-2, 6-linked sialic acid). In addition, H1N1/09 did not only infect the human placenta, but also replicated and was released into the culture media. We concluded that the human placenta is susceptible to the 2009 influenza A virus (H1N1/09) infection, and that particular attention should be paid to shielding pregnant women from infection during influenza season.

Impact of the first wave of the COVID-19 pandemic on birth rates in Europe: a time series analysis in 24 countries

STUDY QUESTION

Did the first wave of the COVID-19 pandemic have an impact on monthly birth rates in Europe?

SUMMARY ANSWER

Using datasets on live births per month in Europe, collected from the Human Fertility Database, we found a -14.1% decline in live births in January 2021 (i.e. 9-10 months after the epidemic peaks and first lockdowns), compared to the average number of live births in January 2018 and 2019.

WHAT IS KNOWN ALREADY

Previous pandemics in the 20th and 21st centuries have been associated with a decline in birth rates 9 months after their peak, and a rebound in births over time. Lockdowns were necessary to control the first wave of the COVID-19 pandemic and may have had an impact on subsequent birth rates.

STUDY DESIGN, SIZE, DURATION

Monthly time series data on live births from January 2018 to March 2021 were extracted to provide a time-series analysis of birthrates during and after the first wave of the COVID-19 pandemic in 24 European countries.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We conducted a random-effect generalized least squares regression to assess the seasonality of births from January 2018 to March 2021, and to identify potential differences in monthly live births after the first wave of the COVID-19 pandemic, considering the seasonality of births. To quantify these potential differences, we estimated the variation rate between the monthly live births observed during 2020 and 2021 and the mean of the 2018-2019 monthly live births in Europe. Factors potentially associated with a variation in monthly birth rates were assessed using univariable and multivariable generalized linear regressions.

MAIN RESULTS AND THE ROLE OF CHANCE

When considering the seasonality of births, January 2021 was the only month with a significant difference in live births. A drop of -14.1% was observed compared to the average number of live births in January 2018 and 2019. At the national level, this drop was observed 9-10 months after the epidemic peaks in 13 countries. The duration of lockdowns was the variable that had the stronger association with this decrease, whereas higher incomes per capita could be a factor limiting this decline. A rebound in births compared to the previous years occurred in March 2021 in 13 countries.

LIMITATIONS, REASONS FOR CAUTION

Our data are based on national data, limiting the power in the multivariable models used and the identification of other potential factors contributing to a decrease or an increase in birth rates. In addition, we collected only live births up to April 2021, which precludes the identification of a difference in births seasonality in 2021.

WIDER IMPLICATIONS OF THE FINDINGS

As with previous pandemics, the COVID-19 outbreak was associated with a decline in births 9 months after its first wave. This trend may be associated with the duration of the lockdowns. Although there was a rebound in births in the following months, it does not seem to compensate for this decline.

STUDY FUNDING/COMPETING INTEREST(S)

The authors receive no external funding and have no conflict of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Investigating COVID-19 transmission and mortality differences between indigenous and non-indigenous populations in Mexico

OBJECTIVES

Indigenous populations have been disproportionately affected during pandemics. We investigated COVID-19 mortality estimates among indigenous and non-indigenous populations at national and sub-national levels in Mexico.

METHODS

We obtained data from the Ministry of Health, Mexico, on 2,173,036 laboratory-confirmed RT-PCR positive COVID-19 cases and 238,803 deaths. We estimated mortality per 1000 person-weeks, mortality rate ratio (RR) among indigenous vs. non-indigenous groups, and hazard ratio (HR) for COVID-19 deaths across four waves of the pandemic, from February 2020 to March 2022. We also assessed differences in the reproduction number (R_t).

RESULTS

The mortality rate among indigenous populations of Mexico was 68% higher than that of non-indigenous groups. Out of 32 federal entities, 23 exhibited higher mortality rates among indigenous groups (P < 0.05 in 13 entities). The fourth wave showed the highest RR (2.40). The crude HR was 1.67 (95% CI: 1.62, 1.72), which decreased to 1.08 (95% CI: 1.04, 1.11) after controlling for other covariates. During the intense fourth wave, the R_t among the two groups was comparable.

CONCLUSION

Indigenous status is a significant risk factor for COVID-19 mortality in Mexico. Our findings may reflect disparities in non-pharmaceutical (e.g., handwashing and using facemasks), and COVID-19 vaccination interventions among indigenous and non-indigenous populations in Mexico.

Geospatial Variability in Excess Death Rates during the COVID-19 Pandemic in Mexico: Examining Socio Demographic, Climate and Population Health Characteristics

Objectives

This study examined how socio-demographic, climate and population health characteristics shaped the geospatial variability in excess mortality patterns during the COVID-19 pandemic in Mexico.

Methods

We used Serfling regression models to estimate all-cause excess mortality rates for all 32 Mexican states. The association between socio-demographic, climate, health indicators and excess mortality rates were determined using multiple linear regression analyses. Functional data analysis characterized clusters of states with distinct excess mortality growth rate curves.

Results

The overall all-cause excess deaths rate during the COVID-19 pandemic in Mexico until April 10, 2021 was estimated at 39.66 per 10 000 population. The lowest excess death rates were observed in southeastern states including Chiapas (12.72) and Oaxaca (13.42), whereas Mexico City had the highest rate (106.17), followed by Tlaxcala (51.99). We found a positive association of excess mortality rates with aging index, marginalization index, and average household size (P < 0.001) in the final adjusted model (Model R²=77%). We identified four distinct clusters with qualitatively similar excess mortality curves.

Conclusion

Central states exhibited the highest excess mortality rates, whereas the distribution of aging index, marginalization index, and average household size explained the variability in excess mortality rates across Mexico.

Why the Navajo Nation was hit so hard by coronavirus: Understanding the disproportionate impact of the COVID-19 pandemic

The COVID-19 (SARS-CoV-2) pandemic of 2019-2020 has incurred astonishing social and economic costs in the United States (US) and worldwide. Native American reservations, representing a unique geography, have been hit much harder than other parts of the country. This study seeks to understand the reasons for the disproportionate impact of the pandemic on Native American communities by focusing on the Navajo Nation - the largest Native American reservation in the US. I first reviewed the historical pandemics experienced by Native Americans. Guided by the literature review, an institutional analysis focusing on the Navajo Nation suggests a lack of both institutional resilience and healthcare preparation. The analysis further identified four factors that could help explain the Navajo's slow response to the COVID-19 pandemic: prevalence of underlying chronic health conditions, lack of institutional resilience, the relationship between the federal government and tribal governments, and lack of social trust. Relevant policy implications are discussed. For instance, to better prepare Native American communities for shocking events like the COVID-19 pandemic in the future, policymaking should integrate informal institutions to build efficient formal institutions for self-governance. Promoting public health education and establishing collaborations between Native and non-Native communities are also necessary long-run strategies.

Temporary Fertility Decline after Large Rubella Outbreak, Japan

Japan experienced 2 large rubella epidemics in 2004 and 2012–2014. Because of suboptimal immunization levels, the country has been experiencing a third major outbreak during 2018–2020. We conducted time series analyses to evaluate the effect of the 2012–2014 nationwide rubella epidemic on prefecture-level natality in Japan. We identified a statistically significant decline in fertility rates associated with rubella epidemic activity and increased Google searches for the term “rubella.” We noted that the timing of fertility declines in 2014 occurred 9–13 months after peak rubella incidence months in 2013 in 4 prefectures with the highest rubella incidence. Public health interventions should focus on enhancing vaccination campaigns against rubella, not only to protect pregnant women from infection but also to mitigate declines in population size and birth rates.

The "saddest repudiation" redux: Structural racism and the unlearned lesson of 1918

The COVID-19 pandemic reveals how the systems and structures of racism devastate the health and well-being of people of color. The debate is an old one and the lesson we have yet to learn was tragically apparent a century ago during the 1918-1919 influenza pandemic. Any history of structural racism in America must begin with the chronicles of African Americans, Native Alaskans, and Indigenous North Americans as they were the originally enslaved and displaced people, subjected to overt and covert policies of oppression ever since. The experiences of Native Alaskans of Bristol Bay Alaska in 1918-1919 present a parallel, illuminating a wrenching example of structural racism that cost lives and impoverished society, then as now. Proven policy solutions exist to remove the structures that produce inequitable health outcomes, but implementing them will require public health officials and policymakers to take multidisciplinary policy actions, to find policy opportunities for change to be made, and, likely, a change in the political environment. The first exists now, the second is afforded because of the current pandemic and the urgent need for policy solutions, and the third is likely coming soon.

Stillbirth Risk during the 1918 Influenza Pandemic in Arizona, USA

The 1918 influenza pandemic, the deadliest pandemic on record, affected approximately 1/3rd of the population worldwide. The impact of this pandemic on stillbirth risk has not been studied in depth. In this study, we assessed the stillbirth risk during the 1918 influenza pandemic in Arizona, USA. We carried out a retrospective study using 21,334 birth records for Maricopa County, Arizona, for the period 1915-1925. We conducted logistic regression analyses to assess the effect of that pandemic on stillbirth risk. Though we did not find a statistically significant impact on stillbirth risk during the pandemic, there was a higher risk of stillbirth in July 1919 (42 stillbirths/1000 births), 9 months after the peak pandemic mortality, and a stillbirth risk of 1.42 (95% CI: 1.17, 1.72) in women ≥35 years compared to the women aged &lt;35 years. The risk of stillbirth was lowest if the mother's age was approximately 26 years at the time of birth. We also report peaks in stillbirth risk 9-10 months after the peak pandemic mortality. Our findings add to our current understanding of the link between pandemic influenza and stillbirth risk.

A Forgotten Danger: Burden of Influenza Mortality Among American Indians and Alaska Natives, 1999-2016

American Indians and Alaska Natives (AI/ANs) are the only racial group in the United States that is identified as having a higher risk for developing influenza-related complications. As such, influenza-related mortality has consistently been one of the leading causes of death among AI/ANs. In addition, estimating influenza-related mortality is hampered by significant degrees of racial misclassification and underreporting of both morbidity and mortality data in the AI/AN population. Using data available from the Centers for Disease Control and Prevention, we analyzed influenza mortality by geography, race, gender, and age group to improve our understanding of the influenza burden on AI/AN communities. We found that while mortality rates generally declined across the AI/AN population, significant disparities exist between AI/ANs and non-Hispanic whites (NHWs). The greatest disparities occurred at the earliest stages of life, with mortality rates for AI/AN children younger than 5 years being more than 2 times higher than for NHW children. Similarly, the burden of influenza-related mortality among AI/AN adults emerged much earlier in life compared with NHWs. Perhaps most important, though, we found significant disparities in the geographic distribution of influenza-related mortality among AI/ANs. Because these are largely vaccine-preventable deaths, these results identify an area for targeted intervention to reduce the overall deaths attributable to influenza.

The 1918 Influenza Pandemic: Looking Back, Looking Forward

In commemoration of the centennial of the 1918 influenza pandemic, the American Journal of Epidemiology has convened a collection of 12 articles that further illuminate the epidemiology of that pandemic and consider whether we would be more prepared if an equally deadly influenza virus were to emerge again. In the present commentary, we place these 12 articles in the context of a growing body of work on the archeo-epidemiology of past pandemics, the socioeconomic and geographic drivers of influenza mortality and natality impact, and renewed interest in immune imprinting mechanisms and the development of novel influenza vaccines. We also highlight persisting mysteries in the origins and severity of the 1918 pandemic and the need to preserve rapidly decaying information that may provide treasure troves for future generations.