2009 pandemic influenza A (H1N1) in pregnancy: a systematic review of the literature

Translating vaccine policy into action: a report from the Bill & Melinda Gates Foundation Consultation on the prevention of maternal and early infant influenza in resource-limited settings

Immunization of pregnant women against influenza is a promising strategy to protect the mother, fetus, and young infant from influenza-related diseases. The burden of influenza during pregnancy, the vaccine immunogenicity during this period, and the robust influenza vaccine safety database underpin recommendations that all pregnant women receive the vaccine to decrease complications of influenza disease during their pregnancies. Recent data also support maternal immunization for the additional purpose of preventing disease in the infant during the first six months of life. In April 2012, the WHO Strategic Advisory Group of Experts (SAGE) on Immunization recommended revisions to the WHO position paper on influenza vaccines. For the first time, SAGE recommended pregnant women should be made the highest priority for inactivated seasonal influenza vaccination. However, the variable maternal influenza vaccination coverage in countries with pre-existing maternal influenza vaccine recommendations underscores the need to understand and to address the discrepancy between recommendations and implementation success. We present the outcome of a multi-stakeholder expert consultation on inactivated influenza vaccination in pregnancy. The creation and implementation of vaccine policies and regulations require substantial resources and capacity. As with all public health interventions, the existence of perceived and real risks of vaccination will necessitate effective and transparent risk communication. Potential risk allocation and sharing mechanisms should be addressed by governments, vaccine manufacturers, and other stakeholders. In resource-limited settings, vaccine-related issues concerning supply, formulation, regulation, evidence evaluation, distribution, cost-utility, and post-marketing safety surveillance need to be addressed. Lessons can be learned from the Maternal and Neonatal Tetanus Elimination Initiative as well as efforts to increase vaccine coverage among pregnant women during the 2009 influenza pandemic. We conclude with an analysis of data gaps and necessary activities to facilitate implementation of maternal influenza immunization programs in resource-limited settings.

Benefits of influenza vaccination during pregnancy for pregnant women

Influenza vaccination is a cornerstone of influenza prevention efforts among pregnant women. Prior to 2005, data from studies conducted on pregnant women were limited, with much of the supporting evidence coming from influenza vaccine studies conducted among nonpregnant, age-matched populations. Since 2005, however, an increasing number of studies have demonstrated the safety and immunogenicity of influenza vaccine for pregnant women, including evidence of maternal transfer of antibody. In addition, the clinical benefit of influenza vaccination, both for the mother and infant, was demonstrated in a landmark randomized clinical trial conducted in Bangladesh. Additional randomized clinical trials with laboratory-confirmed influenza as the primary outcome are underway in countries without a current influenza vaccination program, but such trials are unlikely to be conducted in the United States or other countries that already recommend the vaccination of pregnant women. However, current evidence supports the safety and immunogenicity of inactivated influenza vaccine and its effectiveness in reducing the risk of influenza-related illness among pregnant women.

Effects of influenza on pregnant women and infants

Influenza vaccination during pregnancy has been shown to decrease the risk of influenza and its complications among pregnant women and their infants up to 6 months old. To adequately assess the benefits and potential risks that are associated with the use of influenza vaccine during pregnancy, it is necessary to examine the influenza-associated complications that occur among pregnant women and their children. Pregnant women have been shown to be at increased risk for morbidity and death with influenza illness during seasonal epidemics and pandemics. Newborn infants born to mothers with influenza during pregnancy, especially mothers with severe illness, are at increased risk of adverse outcomes, such as preterm birth and low birthweight. Infants <6 months old who experience influenza virus infection have the highest rates of hospitalization and death of all children. Here we review the risks for influenza-associated complications among pregnant women and infants <6 months old.

The comparative clinical course of pregnant and non-pregnant women hospitalised with influenza A(H1N1)pdm09 infection

INTRODUCTION

The Influenza Clinical Information Network (FLU-CIN) was established to gather detailed clinical and epidemiological information about patients with laboratory confirmed A(H1N1)pdm09 infection in UK hospitals. This report focuses on the clinical course and outcomes of infection in pregnancy.

METHODS

A standardised data extraction form was used to obtain detailed clinical information from hospital case notes and electronic records, for patients with PCR-confirmed A(H1N1)pdm09 infection admitted to 13 sentinel hospitals in five clinical 'hubs' and a further 62 non-sentinel hospitals, between 11th May 2009 and 31st January 2010.Outcomes were compared for pregnant and non-pregnant women aged 15-44 years, using univariate and multivariable techniques.

RESULTS

Of the 395 women aged 15-44 years, 82 (21%) were pregnant; 73 (89%) in the second or third trimester. Pregnant women were significantly less likely to exhibit severe respiratory distress at initial assessment (OR = 0.49 (95% CI: 0.30-0.82)), require supplemental oxygen on admission (OR = 0.40 (95% CI: 0.20-0.80)), or have underlying co-morbidities (p-trend <0.001). However, they were equally likely to be admitted to high dependency (Level 2) or intensive care (Level 3) and/or to die, after adjustment for potential confounders (adj. OR = 0.93 (95% CI: 0.46-1.92). Of 11 pregnant women needing Level 2/3 care, 10 required mechanical ventilation and three died.

CONCLUSIONS

Since the expected prevalence of pregnancy in the source population was 6%, our data suggest that pregnancy greatly increased the likelihood of hospital admission with A(H1N1)pdm09. Pregnant women were less likely than non-pregnant women to have respiratory distress on admission, but severe outcomes were equally likely in both groups.

Possible roles of proinflammatory and chemoattractive cytokines produced by human fetal membrane cells in the pathology of adverse pregnancy outcomes associated with influenza virus infection

Pregnant women are at an increased risk of influenza-associated adverse outcomes, such as premature delivery, based on data from the latest pandemic with a novel influenza A (H1N1) virus in 2009-2010. It has been suggested that the transplacental transmission of influenza viruses is rarely detected in humans. A series of our study has demonstrated that influenza virus infection induced apoptosis in primary cultured human fetal membrane chorion cells, from which a factor with monocyte differentiation-inducing (MDI) activity was secreted. Proinflammatory cytokines, such as interleukin (IL)-6, tumor necrosis factor (TNF)-α, and interferon (IFN)-β, were identified as a member of the MDI factor. Influenza virus infection induced the mRNA expression of not only the proinflammatory cytokines but also chemoattractive cytokines, such as monocyte chemoattractant protein (MCP)-1, regulated on activation, normal T-cell expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-1β, IL-8, growth-regulated oncogene (GRO)-α, GRO-β, epithelial cell-derived neutrophil-activating protein (ENA)-78, and interferon inducible protein (IP)-10 in cultured chorion cells. These cytokines are postulated to associate with human parturition. This paper, therefore, reviews (1) lessons from pandemic H1N1 2009 in pregnancy, (2) production of proinflammatory and chemoattractive cytokines by human fetal membranes and their functions in gestational tissues, and (3) possible roles of cytokines produced by human fetal membranes in the pathology of adverse pregnancy outcomes associated with influenza virus infection.

Immunogenicity of trivalent inactivated influenza vaccination received during pregnancy or postpartum

OBJECTIVE

To estimate the effects of gestational age and other maternal factors on immunologic responses to influenza vaccination.

METHODS

Antepartum and postpartum women receiving influenza vaccination as part of routine clinical care were enrolled through four consecutive vaccination seasons (starting October 2006 through January 2010). Immunologic responses to trivalent inactivated influenza vaccine and monovalent H1N1 were assessed as well as factors influencing vaccine responsiveness. Serum samples were obtained at baseline and 4-8 weeks postvaccination.

RESULTS

Two hundred thirty-nine participants were included in the current analysis. Seroconversion rates to trivalent inactivated influenza vaccine strains were lowest in the first trimester (54.8%) and immediately postpartum (54.8%) and were highest in the late third trimester (69.6%) and late postpartum (69.4%); these differences were not statistically significant (P=.23). In a multivariable model, higher baseline antibody levels (P<.001) and prior year flu vaccination (P=.03) were both significantly associated with reduced odds of seroconversion. Overall, results were consistent when comparing trivalent inactivated influenza vaccine and monovalent pandemic H1N1 responses. Although there was overall no significant association between gestational age at vaccination (P=.23) or prepregnancy body mass index (P=.16), we observed somewhat lower rates of seroconversion for women vaccinated in the first trimester and for obese women.

CONCLUSION

Adequate immunologic responses to inactivated influenza vaccines were demonstrated during pregnancy and the postpartum period. No diminution of immunogenicity was observed in the third trimester, a time of increased clinical vulnerability to influenza.

Review of the pandemic (H1N1) 2009 among pregnant Japanese women

Pregnant women are prone to serious complications when they contract influenza, and a considerable number of pregnant women died from the pandemic (H1N1) 2009 worldwide; however, no maternal mortality occurred in Japan during this pandemic. This review explores the reasons why maternal mortality did not occur in Japan. Two studies conducted during and soon after the pandemic (H1N1) 2009 in Japan suggested the following: 40,000-50,000 pregnant Japanese women took antiviral medicines for prophylaxis after close contact with an infected person; 40% of them (16,000-20,000) contracted the novel influenza and accounted for a half of all 30,000-40,000 pregnant patients with the novel influenza; at least 181 of them required hospitalization; and at least 17 of them developed pneumonitis. Hospitalized women had a 2.5 times higher risk of preterm delivery (at <37 weeks) compared with the general population. The two studies suggested that the following may have contributed to the lack of maternal mortality in Japan: (i) more than 60% of candidates were vaccinated within 1.5 months after the availability of a vaccine against the novel virus; (ii) vaccination reduced the infection rate by 89%; (iii) a large number of women took antiviral drugs before symptom onset after close contact with an infected person; and (iv) approximately 90% of hospitalized pregnant patients took antiviral drugs within 48 hours after symptom onset.

2009 H1N1 vaccination by pregnant women during the 2009-10 H1N1 influenza pandemic

OBJECTIVE

Pregnant women were identified at greater risk and given priority for 2009 H1N1 vaccination during the 2009 through 2010 H1N1 pandemic. We identified factors associated with acceptance or refusal of 2009 H1N1 vaccination during pregnancy.

STUDY DESIGN

We conducted an in-person survey of postpartum women on the labor and delivery service from June 17 through Aug. 13, 2010, at 4 New York hospitals.

RESULTS

Of 1325 survey respondents, 34.2% received 2009 H1N1 vaccination during pregnancy. A provider recommendation was most strongly associated with vaccine acceptance (odds ratio [OR], 19.4; 95% confidence interval [CI], 12.7-31.1). Also more likely to take vaccine were women indicating the vaccine was safe for the fetus (OR, 12.4; 95% CI, 8.3-19.0) and those who previously took seasonal flu vaccination (OR, 7.9; 95% CI, 5.8-10.7). Race, education, income, and age were less important in accepting vaccine.

CONCLUSION

Greater emphasis on vaccine safety and provider recommendation is needed to increase the number of women vaccinated during pregnancy.

Maternal deaths in women with lupus nephritis: a review of published evidence

BACKGROUND AND OBJECTIVES

Pregnancies in women with systemic lupus erythematosus (SLE) and lupus nephritis are considered high-risk due to high rates of maternal and fetal complications. However, there has not been a formal analysis addressing the issue of maternal deaths in these women. The aim of this study was to perform a literature review of the maternal deaths in women with SLE and lupus nephritis to: (1) identify the main causes of death and (2) discuss possible reasons for these causes, and strategies that may improve patient care and outcomes. DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENT: We performed an extensive electronic literature search from 1962 to 2009 using online databases (PubMed, Embase, Lilacs, Cochrane Controlled Trials Register, Medline, and Science Citation Index). Studies were included if they reported pregnancies in patients with SLE and lupus nephritis with at least one reported maternal death.

RESULTS

We identified 13 studies that reported a total of 17 deaths in the 6 week post-partum period that were attributable to SLE and lupus nephritis. In all cases, death occurred in the setting of active disease, and was attributed either to infection in 41.2% (n = 7), or disease activity in 29.4% (n = 5). The remaining deaths were due to pulmonary embolus in 11.8% (n = 2), pregnancy-associated cardiomyopathy in 5.9% (n = 1), adrenal failure due to abrupt steroid withdrawal in 5.9% (n = 1), and undefined in 5.9% (n = 1).

CONCLUSIONS

All maternal deaths in patients with SLE and lupus nephritis occurred in those with active disease, with disease activity/complications and infections (mainly opportunistic) being the two major causes. The presented evidence further supports timing of pregnancy relative to SLE activity, and the judicious use of immunosuppressive agents in pregnant patients.

H1N1 Influenza Viral Infection in a Postpartum Young Woman Causes Respiratory Failure: What the Care Providers Ought to Know?

Pregnant and postpartum women are considered a population at increased risk of hospitalization of H1N1 infection. We report the case of a young postpartum woman, who developed evidence of respiratory failure reaching the point of requiring intubation due to an H1N1 influenza virus infection two days after a caesarean delivery. We emphasize the diagnosis, management, and the outcome focusing on the question “what the care providers, including obstetric health care workers, ought to know?” Diagnostic and management strategy for pregnant or postpartum women with novel influenza A (H1N1) viral infection and increased awareness amongst patients and health care professionals may result in improved survival.

Complications of the 2009 influenza A/H1N1 pandemic in pregnant women in The Netherlands: a national cohort study

The 2009 influenza A/H1N1 pandemic caused an increase in complications in pregnant women. To be well prepared for a next pandemic, we investigated the obstetric and maternal complications of this pandemic. In our national cohort of 59 pregnant women who were admitted to the hospital, no major complications apart from preterm birth and admission to the neonatal intensive care unit were observed. Although the small size of this study precludes us drawing any definitive conclusions, comparing our results with those in other countries suggests that the influenza A/H1N1 pandemic had a relatively benign course in pregnant women in The Netherlands.

Immunogenicity of an inactivated monovalent 2009 H1N1 influenza vaccine in pregnant women

BACKGROUND

Although pregnant women are at increased risk of severe illness following influenza infection, there is relatively little information on the immunogenicity of influenza vaccines administered during pregnancy.

METHODS

We conducted a clinical trial that enrolled 120 pregnant women in which participants were randomly assigned to receive an inactivated 2009 H1N1 influenza vaccine containing either 25 μg or 49 μg of hemagglutinin (HA) in a 2-dose series with a 21-day period between administration of the first and second doses.

RESULTS

Following the first vaccination, HA inhibition (HAI) titers of ≥1:40 were detected in 93% (95% confidence interval [CI], 82%-98%) of subjects who received the 25-μg dose and 97% (95% CI, 88%-100%) of subjects receiving the 49-μg dose. In cord blood samples, HAI titers of ≥1:40 were found in 87% (95% CI, 73%-96%) of samples from the 25-μg dose group and in 89% (95% CI, 76%-96%) from the 49-μg dose group. Microneutralization titers tended to be higher than HAI titers, but the patterns of response were similar.

CONCLUSIONS

In pregnant women, 1 dose of an inactivated 2009 H1N1 influenza vaccine containing 25 μg of HA elicited an antibody response typically associated with protection against influenza infection. Efficient transplacental transfer of antibody was also documented.

Progress towards Millennium Development Goals 4 and 5 on maternal and child mortality: an updated systematic analysis

BACKGROUND

With 4 years until 2015, it is essential to monitor progress towards Millennium Development Goals (MDGs) 4 and 5. Although estimates of maternal and child mortality were published in 2010, an update of estimates is timely in view of additional data sources that have become available and new methods developed. Our aim was to update previous estimates of maternal and child mortality using better data and more robust methods to provide the best available evidence for tracking progress on MDGs 4 and 5.

METHODS

We update the analyses of the progress towards MDGs 4 and 5 from 2010 with additional surveys, censuses, vital registration, and verbal autopsy data. For children, we estimate early neonatal (0-6 days), late neonatal (7-28 days), postneonatal (29-364 days), childhood (ages 1-4 years), and under-5 mortality. We use an improved model for estimating mortality by age under 5 years. For maternal mortality, our updated analysis includes greater than 1000 additional site-years of data. We tested a large set of alternative models for maternal mortality; we used an ensemble model based on the models with the best out-of-sample predictive validity to generate new estimates from 1990 to 2011.

FINDINGS

Under-5 deaths have continued to decline, reaching 7·2 million in 2011 of which 2·2 million were early neonatal, 0·7 million late neonatal, 2·1 million postneonatal, and 2·2 million during childhood (ages 1-4 years). Comparing rates of decline from 1990 to 2000 with 2000 to 2011 shows that 106 countries have accelerated declines in the child mortality rate in the past decade. Maternal mortality has also continued to decline from 409,100 (uncertainty interval 382,900-437,900) in 1990 to 273,500 (256,300-291,700) deaths in 2011. We estimate that 56,100 maternal deaths in 2011 were HIV-related deaths during pregnancy. Based on recent trends in developing countries, 31 countries will achieve MDG 4, 13 countries MDG 5, and nine countries will achieve both.

INTERPRETATION

Even though progress on reducing maternal and child mortality in most countries is accelerating, most developing countries will take many years past 2015 to achieve the targets of the MDGs 4 and 5. Similarly, although there continues to be progress on maternal mortality the pace is slow, without any overall evidence of acceleration. Immediate concerted action is needed for a large number of countries to achieve MDG 4 and MDG 5.

FUNDING

Bill & Melinda Gates Foundation.

Influenza vaccine for pregnant women in resource-constrained countries: a review of the evidence to inform policy decisions

Seasonal influenza is responsible for three to five million severe cases of disease annually, and up to 500,000 deaths worldwide. Pregnant women and infants suffer disproportionately from severe outcomes of influenza. The excellent safety profile and reliable immunogenicity of inactivated influenza vaccine support WHO recommendations that pregnant women be vaccinated to decrease complications of influenza disease during pregnancy. Nevertheless, influenza vaccine is not routinely used in most low-and middle-income countries and is not widely used in pregnant women worldwide. Two recent prospective, controlled trials of maternal influenza vaccination in Bangladesh and US Native American reservations demonstrated that inactivated influenza vaccine given to pregnant women can decrease laboratory-confirmed influenza virus infection in their newborn children. These studies support consideration of the feasibility of targeted influenza vaccine programs in resource-constrained countries. Platforms exist for the delivery of influenza vaccine to pregnant women worldwide. Even in the least developed countries, an estimated 70% of women receive antenatal care, providing an opportunity for targeted influenza vaccination. Challenges to the introduction of maternal influenza vaccination in resource-constrained countries exist, including issues regarding vaccine formulation, availability, and cost. Nonetheless, maternal influenza vaccination remains an important and potentially cost-effective approach to decrease influenza morbidity in two high-risk groups - pregnant women and young infants.