Incidence of influenza during pregnancy and association with pregnancy and perinatal outcomes in three middle-income countries: a multisite prospective longitudinal cohort study

[Fetal death: Expert consensus from the College of French Gynecologists and Obstetricians]

Fetal death is defined as the spontaneous cessation of cardiac activity after fourteen weeks of amenorrhea. In France, the prevalence of fetal death after 22 weeks is between 3.2 and 4.4/1000 births. Regarding the prevention of fetal death in the general population, it is not recommended to counsel for rest and not to prescribe vitamin A, vitamin D nor micronutrient supplementation for the sole purpose of reducing the risk of fetal death (Weak recommendations; Low quality of evidence). It is not recommended to prescribe aspirin (Weak recommendation; Very low quality of evidence). It is recommended to offer vaccination against influenza in epidemic periods and against SARS-CoV-2 (Strong recommendations; Low quality of evidence). It is not recommended to systematically look for nuchal cord encirclements during prenatal screening ultrasounds (Strong Recommendation; Low Quality of Evidence) and not to perform systematic antepartum monitoring by cardiotocography (Weak Recommendation; Very Low Quality of Evidence). It is not recommended to ask women to perform an active fetal movement count to reduce the risk of fetal death (Strong Recommendation; High Quality of Evidence). Regarding evaluation in the event of fetal death, it is suggested that an external fetal examination be systematically offered (Expert opinion). It is recommended that a fetopathological and anatomopathological examination of the placenta be carried out to participate in cause identification (Strong Recommendation. Moderate quality of evidence). It is recommended that chromosomal analysis by microarray testing be performed rather than conventional karyotype, in order to be able to identify a potentially causal anomaly more frequently (Strong Recommendation, moderate quality of evidence); to this end, it is suggested that postnatal sampling of the placental fetal surface for genetic purposes be preferred (Expert Opinion). It is suggested to test for antiphospholipid antibodies and systematically perform a Kleihauer test and a test for irregular agglutinins (Expert opinion). It is suggested to offer a summary consultation, with the aim of assessing the physical and psychological status of the parents, reporting the results, discussing the cause and providing information on monitoring for a subsequent pregnancy (Expert opinion). Regarding announcement and support, it is suggested to announce fetal death without ambiguity, using simple words and adapting to each situation, and then to support couples with empathy in the various stages of their care (Expert opinion). Regarding management, it is suggested that, in the absence of a situation at risk of disseminated intravascular coagulation or maternal vitality, the patient's wishes should be taken into account when determining the time between the diagnosis of fetal death and induction of birth. Returning home is possible if it's the patient wish (Expert opinion). In all situations excluding maternal life-threatening emergencies, the preferred mode of delivery is vaginal delivery, regardless the history of cesarean section(s) history (Expert opinion). In the event of fetal death, it is recommended that mifepristone 200mg be prescribed at least 24hours before induction, to reduce the delay between induction and delivery (Low recommendation. Low quality of evidence). There are insufficient data in the literature to make a recommendation regarding the route of administration (vaginal or oral) of misoprostol, neither the type of prostaglandin to reduce induction-delivery time or maternal morbidity. It is suggested that perimedullary analgesia be introduced at the start of induction if the patient asks, regardless of gestational age. It is suggested to prescribe cabergoline immediately in the postpartum period in order to avoid lactation, whatever the gestational age, after discussing the side effects of the treatment with the patient (Expert opinion). The risk of recurrence of fetal death after unexplained fetal death does not appear to be increased in subsequent pregnancies, and data from the literature are insufficient to make a recommendation on the prescription of aspirin. In the event of a history of fetal death due to vascular issues, low-dose aspirin is recommended to reduce perinatal morbidity, and should not be combined with heparin therapy (Low recommendation, very low quality of evidence). It is suggested not to recommend an optimal delay before initiating another pregnancy just because of the history of fetal death. It is suggested that the woman and co-parent be informed of the possibility of psychological support. Fetal heart rate monitoring is not indicated solely because of a history of fetal death. It is suggested that delivery not be systematically induced. However, induction can be considered depending on the context and parental request. The gestational age will be discussed, taking into account the benefits and risks, especially before 39 weeks. If a cause of fetal death is identified, management will be adapted on a case-by-case basis (expert opinion). In the event of fetal death occurring in a twin pregnancy, it is suggested that the surviving twin be evaluated as soon as the diagnosis of fetal death is made. In the case of dichorionic pregnancy, it is suggested to offer ultrasound monitoring on a monthly basis. It is suggested not to deliver prematurely following fetal death of a twin. If fetal death occurs in a monochorionic twin pregnancy, it is suggested to contact the referral competence center, in order to urgently look for signs of acute fetal anemia on ultrasound in the surviving twin, and to carry out weekly ultrasound monitoring for the first month. It is suggested not to induce birth immediately.

Pregnancy enhances antiviral immunity independent of type I IFN but dependent on IL-17-producing γδ+ T cells in the nasal mucosa

Pregnancy is associated with profound changes in immunity. However, pregnancy-related respiratory immune adaptations in response to influenza infection and their impact on disease severity remain unclear. Here, we describe, in a preclinical model of mid-gestation pregnancy, a mechanism of enhanced host defense against influenza A virus (IAV) localized to the nasal cavity that limits viral replication and reduces the magnitude of intrapulmonary immune responses. Consequently, the pregnant mice show reduced pulmonary pathology and preserved airway function after IAV infection. The early restriction of viral replication is independent of type I interferon (IFN) but dependent on increased antimicrobial peptides (AMPs) driven by interleukin-17+ (IL-17+) γδ+ T cells within the nasal passages. This pathway of host defense against IAV infection in the upper airways during pregnancy restricts early viral infection and prevents virus dissemination into the lung supporting maternal fitness.

Acceptance and uptake of vaccines against tetanus, influenza, pertussis, and COVID-19 among pregnant and postpartum women in low- and middle-income countries: a systematic review and meta-analysis protocol

BACKGROUND

Pregnant women, fetuses, and neonates are particularly vulnerable to vaccine-preventable diseases (VPDs). These VPDs are associated with high morbidity and mortality among expectant mothers and their fetuses and neonates. Vaccination during pregnancy can protect the expectant mother from VPDs to which she may be especially vulnerable while pregnant. In addition, the passive transfer of maternal neutralizing immunoglobulin G (IgG) and secretory immunoglobulin A (IgA) also protects the fetus against congenital infections and may further protect the neonate from infection during the first few months of life. Despite this, coverage of recommended maternal vaccines remains suboptimal globally, especially in resource-constrained settings. Determinants of vaccine acceptance and uptake are frequently understudied in low- and middle-income countries (LMICs) and among specific groups such as pregnant and postpartum women. This proposed systematic review will assess the acceptance and uptake of vaccines against tetanus, influenza, pertussis, and COVID-19 among pregnant and postpartum women in LMICs.

METHODS

A Boolean search strategy employing common and medical subject heading (MeSH) terms for tetanus, influenza, pertussis, and COVID-19 vaccines, as well as vaccine acceptance, hesitancy, together with uptake, pregnancy, and postpartum, will be used to search electronic databases for relevant literature published between 2009 and 2024. Only studies conducted in LMICs that investigated determinants of acceptance, hesitancy, and uptake of tetanus, influenza, pertussis, and COVID-19 vaccines among pregnant and postpartum women will be eligible for inclusion in the review. The quality and the risk of bias of all eligible full-text articles will be assessed using the Joanna Briggs Institute's (JBI) critical appraisal tools.

DISCUSSION

This protocol proposes a systematic review and meta-analysis that aims to assess the uptake of maternal vaccines and to systematically appraise and quantify determinants of the acceptance and uptake of recommended vaccines during pregnancy and postpartum in LMICs. A better understanding of these factors and how they influence maternal vaccine decision-making will enable public health practitioners as well as global and national policymakers to design more effective interventions as we look towards expanding the scope and reach of maternal immunization programs.

Influenza Infection During Pregnancy and Risk of Seizures in Offspring

Importance

Seizure is a common neurological problem among infants and children up to age 6 years. Prenatal exposure to maternal influenza infection has been reported to be associated with childhood seizures.

Objective

To evaluate the association between maternal influenza infection and risk of childhood seizures.

Designs, Setting, and Participants

This cohort study identified mother-offspring pairs from January 1, 2004, to December 31, 2013, using records in Taiwan's Maternal and Child Health Database. Mothers who had influenza infection during pregnancy and their first offspring were identified and assigned to the influenza group. Mothers in the control group were those without influenza during pregnancy and were matched 1:4 with mothers in the influenza group by maternal age, offspring sex, and date of delivery. Offspring were followed up until December 31, 2020. Data were analyzed between March 2023 and July 2024.

Exposure

Diagnosis of influenza infection during pregnancy defined using International Classification of Diseases, Ninth Revision, Clinical Modification codes 487.0, 487.1, and 487.8, or International Statistical Classification of Diseases, Tenth Revision, Clinical Modification codes J09, J10, and J11.

Main Outcomes and Measures

The primary outcome was the association between maternal influenza infection during pregnancy and risk of any type of seizures during childhood, including both epilepsy and febrile seizures. Adjusted hazard ratios (AHRs) and 95% CIs were estimated using Cox proportional hazards regression models. Pregnancy-related complications were collected as covariates.

Results

A total of 1 316 107 mother-offspring pairs were enrolled, of whom 75 835 mothers (predominant maternal age, 25-29 years; 39 324 male offspring [51.9%]) were assigned to the influenza group and 1 240 272 were matched and assigned to the control group (n = 303 340; predominant maternal age, 30-34 years; 157 296 male offspring [51.9%]). In the influenza group, there was a slightly higher prevalence of placenta previa or abruption compared with the control group (1.6% [1241] vs 1.4% [4350]; P < .001). The cumulative risk of seizures was higher among offspring whose mothers had influenza infection. After controlling for potential confounders, the AHRs were 1.09 (95% CI, 1.05-1.14) for seizures, 1.11 (95% CI, 1.06-1.17) for febrile convulsions, and 1.04 (95% CI, 0.97-1.13) for epilepsy. In the subgroup analysis, no statistically significant differences were observed between the trimesters regarding the timing of influenza infection.

Conclusions and Relevance

Results of this cohort study suggest that maternal influenza infection during pregnancy was associated with an increased risk of childhood seizures, especially febrile seizures, but not epilepsy. Further studies are needed to elucidate the mechanisms underlying childhood neurological development.

Brain region-specific alterations in gene expression trajectories in the offspring born from influenza A virus infected mice

Influenza A virus (IAV) infection during pregnancy can increase the risk for neurodevelopmental disorders in the offspring, however, the underlying neurobiological mechanisms are largely unknown. To recapitulate viral infection, preclinical studies have traditionally focused on using synthetic viral mimetics, rather than live IAV, to examine consequences of maternal immune activation (MIA)-dependent processes on offspring. In contrast, few studies have used live IAV to assess effects on global gene expression, and none to date have addressed whether moderate IAV, mimicking seasonal influenza disease, alters normal gene expression trajectories in different brain regions across different stages of development. Herein, we show that moderate IAV infection during pregnancy, which causes mild maternal disease and no overt foetal complications in utero, induces lasting effects on the offspring into adulthood. We observed behavioural changes in adult offspring, including disrupted prepulse inhibition, dopaminergic hyper-responsiveness, and spatial recognition memory deficits. Gene profiling in the offspring brain from neonate to adolescence revealed persistent alterations to normal gene expression trajectories in the prefronal cortex, hippocampus, hypothalamus and cerebellum. Alterations were found in genes involved in inflammation and neurogenesis, which were predominately dysregulated in neonatal and early adolescent offspring. Notably, late adolescent offspring born from IAV infected mice displayed altered microglial morphology in the hippocampus. In conclusion, we show that moderate IAV during pregnancy perturbs neurodevelopmental trajectories in the offspring, including alterations in the neuroinflammatory gene expression profile and microglial number and morphology in the hippocampus, resulting in behavioural changes in adult offspring. Such early perturbations may underlie the vulnerability in human offspring for the later development of neurodevelopmental disorders, including schizophrenia. Our work highlights the importance of using live IAV in developing novel preclinical models that better recapitulate the real-world impact of inflammatory insults during pregnancy on offspring neurodevelopmental trajectories and disease susceptibility later in life.

Evaluating Factors That Influence Influenza Vaccination Uptake among Pregnant People in a Medically Underserved Area in Washington State

INTRODUCTION

Despite substantial evidence demonstrating the effectiveness of influenza vaccines, only 38.6% of the adult United States population received an influenza vaccine during the 2023-2024 flu season. Vaccination rates are typically lower among U.S. minority groups, and in 2022, pregnant persons from U.S. minority racial and ethnic groups showed a decrease in influenza vaccine coverage.

METHODS

A survey was conducted with residents of Yakima County, Washington, which is home to one of the state's largest percentages of people who identify as Hispanic or Latino/a. The objective was to evaluate the uptake of influenza vaccine among pregnant persons. Surveys were sent to a random sample of 3000 residential mailing addresses. Of the 500 respondents, 244 (52.1%) reported that they had been pregnant, with those identifying as Hispanic or Latino/a constituting 23.8% of this total. Only 62 (26.2%) reported being immunized against influenza during pregnancy. Respondents who were immunized against influenza chose to be vaccinated to protect themselves from the flu (85.5%, n = 53); because a healthcare provider recommended getting vaccinated (85.5%, n = 53); to protect the baby from the flu (82.3%, n = 51); because it was available for free or low cost (62.9%, n = 39); and because vaccination was convenient (54.8%, n = 34). Qualitative evaluation identified that participants who were not vaccinated against influenza during pregnancy believed the vaccination was not needed, was not recommended by a healthcare provider, was difficult to access, they were against vaccination in general, or they were concerned about the safety and ingredients of the vaccine.

CONCLUSION

Barriers to vaccination identified in this study included vaccine distrust, lack of awareness, and concerns about vaccine efficacy and safety. Healthcare providers can help address these concerns by providing education and recommendations about the importance of influenza vaccination during pregnancy.

Influenza A virus during pregnancy disrupts maternal intestinal immunity and fetal cortical development in a dose- and time-dependent manner

Epidemiological studies link exposure to viral infection during pregnancy, including influenza A virus (IAV) infection, with increased incidence of neurodevelopmental disorders (NDDs) in offspring. Models of maternal immune activation (MIA) using viral mimetics demonstrate that activation of maternal intestinal T helper 17 (TH17) cells, which produce effector cytokine interleukin (IL)-17, leads to aberrant fetal brain development, such as neocortical malformations. Fetal microglia and border-associated macrophages (BAMs) also serve as potential cellular mediators of MIA-induced cortical abnormalities. However, neither the inflammation-induced TH17 cell pathway nor fetal brain-resident macrophages have been thoroughly examined in models of live viral infection during pregnancy. Here, we inoculated pregnant mice with two infectious doses of IAV and evaluated peak innate and adaptive immune responses in the dam and fetus. While respiratory IAV infection led to dose-dependent maternal colonic shortening and microbial dysregulation, there was no elevation in intestinal TH17 cells nor IL-17. Systemically, IAV resulted in consistent dose- and time-dependent increases in IL-6 and IFN-γ. Fetal cortical abnormalities and global changes in fetal brain transcripts were observable in the high-but not the moderate-dose IAV group. Profiling of fetal microglia and BAMs revealed dose- and time-dependent differences in the numbers of meningeal but not choroid plexus BAMs, while microglial numbers and proliferative capacity of Iba1+ cells remained constant. Fetal brain-resident macrophages increased phagocytic CD68 expression, also in a dose- and time-dependent fashion. Taken together, our findings indicate that certain features of MIA are conserved between mimetic and live virus models, while others are not. Overall, we provide consistent evidence of an infection severity threshold for downstream maternal inflammation and fetal cortical abnormalities, which recapitulates a key feature of the epidemiological data and further underscores the importance of using live pathogens in NDD modeling to better evaluate the complete immune response and to improve translation to the clinic.

Pathogenesis of viral infections during pregnancy

SUMMARYViral infections during pregnancy are associated with significant adverse perinatal and fetal outcomes. Pregnancy is a unique immunologic and physiologic state, which can influence control of virus replication, severity of disease, and vertical transmission. The placenta is the organ of the maternal-fetal interface and provides defense against microbial infection while supporting the semi-allogeneic fetus via tolerogenic immune responses. Some viruses, such as cytomegalovirus, Zika virus, and rubella virus, can breach these defenses, directly infecting the fetus and having long-lasting consequences. Even without direct placental infection, other viruses, including respiratory viruses like influenza viruses and severe acute respiratory syndrome coronavirus 2, still cause placental damage and inflammation. Concentrations of progesterone and estrogens rise during pregnancy and contribute to immunological adaptations, placentation, and placental development and play a pivotal role in creating a tolerogenic environment at the maternal-fetal interface. Animal models, including mice, nonhuman primates, rabbits, and guinea pigs, are instrumental for mechanistic insights into the pathogenesis of viral infections during pregnancy and identification of targetable treatments to improve health outcomes of pregnant individuals and offspring.

Mathematical Modeling Suggests That Monocyte Activity May Drive Sex Disparities during Influenza Infection

In humans, females of reproductive age often experience a more severe disease during influenza A virus infection, which may be due to differences in their innate immune response. Sex-specific outcomes to influenza infection have been recapitulated in mice, enabling researchers to study viral and immune dynamics in vivo in order to identify immune mechanisms that are differently regulated between the sexes. This study is based on the hypothesis that sex-specific outcomes emerge due to differences in the rates/speeds that select immune components respond. Using publicly available sex-specific murine data, we utilized dynamic mathematical models of the innate immune response to identify candidate mechanisms that may lead to increased disease severity in female mice. We implemented a large computational screen using the Bayesian information criterion (BIC), wherein the goodness of fit of the competing model scenarios is balanced against complexity (i.e., the number of parameters). Our results suggest that having sex-specific rates for proinflammatory monocyte induction by interferon and monocyte inhibition of virus replication provides the simplest (lowest BIC) explanation for the difference observed in the male and female immune responses. Markov-chain Monte Carlo (MCMC) analysis and global sensitivity analysis of the top performing scenario were performed to provide rigorous estimates of the sex-specific parameter distributions and to provide insight into which parameters most affect innate immune responses. Simulations using the top-performing model suggest that monocyte activity could be a key target to reduce influenza disease severity in females. Overall, our Bayesian statistical and dynamic modeling approach suggests that monocyte activity and induction parameters are sex-specific and may explain sex-differences in influenza disease immune dynamics.

COVID-19 Vaccination Strategies in the Endemic Period: Lessons from Influenza

Coronavirus disease 2019 (COVID-19) is a highly contagious zoonotic respiratory disease with many similarities to influenza. Effective vaccines are available for both; however, rapid viral evolution and waning immunity make them virtually impossible to eradicate with vaccines. Thus, the practical goal of vaccination is to reduce the incidence of serious illnesses and death. Three years after the introduction of COVID-19 vaccines, the optimal vaccination strategy in the endemic period remains elusive, and health authorities worldwide have begun to adopt various approaches. Herein, we propose a COVID-19 vaccination strategy based on the data available until early 2024 and discuss aspects that require further clarification for better decision making. Drawing from comparisons between COVID-19 and influenza vaccination strategies, our proposed COVID-19 vaccination strategy prioritizes high-risk groups, emphasizes seasonal administration aligned with influenza vaccination campaigns, and advocates the co-administration with influenza vaccines to increase coverage.

Estimating averted illnesses from influenza vaccination for children and pregnant women - El Salvador, Panama, and Peru, 2011-2018

BACKGROUND

Estimating the burden of disease averted by vaccination can assist policymakers to implement, adjust, and communicate the value of vaccination programs. Demonstrating the use of a newly available modeling tool, we estimated the burden of influenza illnesses averted by seasonal influenza vaccination in El Salvador, Panama, and Peru during 2011-2017 among two influenza vaccine target populations: children aged 6-23 months and pregnant women.

METHODS

We derived model inputs, including incidence, vaccine coverage, vaccine effectiveness, and multipliers from publicly available country-level influenza surveillance data and cohort studies. We also estimated changes in illnesses averted when countries' vaccine coverage was achieved using four different vaccine deployment strategies.

RESULTS

Among children aged 6-23 months, influenza vaccination averted an estimated cumulative 2,161 hospitalizations, 81,907 medically-attended illnesses, and 126,987 overall illnesses during the study period, with a prevented fraction ranging from 0.3 % to 12.5 %. Among pregnant women, influenza vaccination averted an estimated cumulative 173 hospitalizations, 6,122 medically attended illnesses, and 16,412 overall illnesses, with a prevented fraction ranging from 0.2 % to 10.9 %. Compared to an influenza vaccine campaign with equal vaccine distribution during March-June, scenarios in which total cumulative coverage was achieved in March and April consistently resulted in the greatest increase in averted illness (23 %-3,129 % increase among young children and 22 %-3,260 % increase among pregnant women).

DISCUSSION

Influenza vaccination campaigns in El Salvador, Panama, and Peru conducted between 2011 and 2018 prevented hundreds to thousands of influenza-associated hospitalizations and illnesses in young children and pregnant women. Existing vaccination programs could prevent additional illnesses, using the same number of vaccines, by achieving the highest possible coverage within the first two months of an influenza vaccine campaign.

COVID-19 in pregnant women: a systematic review and meta-analysis on the risk and prevalence of pregnancy loss

BACKGROUND

Pregnant women infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are more likely to experience preterm birth and their neonates are more likely to be stillborn or admitted to a neonatal unit. The World Health Organization declared in May 2023 an end to the coronavirus disease 2019 (COVID-19) pandemic as a global health emergency. However, pregnant women are still becoming infected with SARS-CoV-2 and there is limited information available regarding the effect of SARS-CoV-2 infection in early pregnancy on pregnancy outcomes.

OBJECTIVE AND RATIONALE

We conducted this systematic review to determine the prevalence of early pregnancy loss in women with SARS-Cov-2 infection and compare the risk to pregnant women without SARS-CoV-2 infection.

SEARCH METHODS

Our systematic review is based on a prospectively registered protocol. The search of PregCov19 consortium was supplemented with an extra electronic search specifically on pregnancy loss in pregnant women infected with SARS-CoV-2 up to 10 March 2023 in PubMed, Google Scholar, and LitCovid. We included retrospective and prospective studies of pregnant women with SARS-CoV-2 infection, provided that they contained information on pregnancy losses in the first and/or second trimester. Primary outcome was miscarriage defined as a pregnancy loss before 20 weeks of gestation, however, studies that reported loss up to 22 or 24 weeks were also included. Additionally, we report on studies that defined the pregnancy loss to occur at the first and/or second trimester of pregnancy without specifying gestational age, and for second trimester miscarriage only when the study presented stillbirths and/or foetal losses separately from miscarriages. Data were stratified into first and second trimester. Secondary outcomes were ectopic pregnancy (any extra-uterine pregnancy), and termination of pregnancy. At least three researchers independently extracted the data and assessed study quality. We calculated odds ratios (OR) and risk differences (RDs) with corresponding 95% CI and pooled the data using random effects meta-analysis. To estimate risk prevalence, we performed meta-analysis on proportions. Heterogeneity was assessed by I2.

OUTCOMES

We included 120 studies comprising a total of 168 444 pregnant women with SARS-CoV-2 infection; of which 18 233 women were in their first or second trimester of pregnancy. Evidence level was considered to be of low to moderate certainty, mostly owing to selection bias. We did not find evidence of an association between SARS-CoV-2 infection and miscarriage (OR 1.10, 95% CI 0.81-1.48; I2 = 0.0%; RD 0.0012, 95% CI -0.0103 to 0.0127; I2 = 0%; 9 studies, 4439 women). Miscarriage occurred in 9.9% (95% CI 6.2-14.0%; I2 = 68%; 46 studies, 1797 women) of the women with SARS CoV-2 infection in their first trimester and in 1.2% (95% CI 0.3-2.4%; I2 = 34%; 33 studies; 3159 women) in the second trimester. The proportion of ectopic pregnancies in women with SARS-CoV-2 infection was 1.4% (95% CI 0.02-4.2%; I2 = 66%; 14 studies, 950 women). Termination of pregnancy occurred in 0.6% of the women (95% CI 0.01-1.6%; I2 = 79%; 39 studies; 1166 women).

WIDER IMPLICATIONS

Our study found no indication that SARS-CoV-2 infection in the first or second trimester increases the risk of miscarriages. To provide better risk estimates, well-designed studies are needed that include pregnant women with and without SARS-CoV-2 infection at conception and early pregnancy and consider the association of clinical manifestation and severity of SARS-CoV-2 infection with pregnancy loss, as well as potential confounding factors such as previous pregnancy loss. For clinical practice, pregnant women should still be advised to take precautions to avoid risk of SARS-CoV-2 exposure and receive SARS-CoV-2 vaccination.

Prenatal Maternal Immunization for Infant Protection: A Review of the Vaccines Recommended, Infant Immunity and Future Research Directions

Prenatal maternal immunization is an effective tool to protect mothers and infants from poor health outcomes due to infectious diseases. We provide an overview of the rationale for the use of prenatal vaccines, discuss the immunologic environment of the maternal-fetal interface including the impact of maternal vaccines prenatally and subsequently on the infant's immune response, and review vaccines currently recommended in pregnancy and landscape for the future of maternal vaccination. This review aims to provide an understanding of the recent history and progress made in the field and highlight the importance of continued research and development into new vaccines for pregnant populations.

Evaluation of cesarean delivery rates and factors associated with cesarean delivery among women enrolled in a pregnancy cohort study at two tertiary hospitals in Thailand

BACKGROUND

Cesarean delivery rates have increased globally resulting in a public health concern. We estimate rates of cesarean deliveries among Thai women using the World Health Organization (WHO) Robson Classification system and compare rates by Robson group to the Robson guideline for acceptable rates to identify groups that might benefit most from interventions for rate reduction.

METHODS

In 2017 and 2018, we established cohorts of pregnant women aged ≥ 18 years seeking prenatal care at two tertiary Thai hospitals and followed them until 6-8 weeks postpartum. Three in-person interviews (enrollment, end of pregnancy, and postpartum) were conducted using structured questionnaires to obtain demographic characteristics, health history, and delivery information. Cesarean delivery indication was classified based on core obstetric variables (parity, previous cesarean delivery, number of fetuses, fetal presentation, gestational week, and onset of labor) assigned to 10 groups according to the Robson Classification. Logistic regression was used to identify factors associated with cesarean delivery among nulliparous women with singleton, cephalic, term pregnancies.

RESULTS

Of 2,137 participants, 970 (45%) had cesarean deliveries. The median maternal age at delivery was 29 years (interquartile range, 25-35); 271 (13%) participants had existing medical conditions; and 446 (21%) had pregnancy complications. The cesarean delivery rate varied by Robson group. Multiparous women with > 1 previous uterine scar, with a single cephalic pregnancy, ≥ 37 weeks gestation (group 5) contributed the most (14%) to the overall cesarean rate, whereas those with a single pregnancy with a transverse or oblique lie, including women with previous uterine scars (group 9) contributed the least (< 1%). Factors independently associated with cesarean delivery included age ≥ 25 years, pre-pregnancy obesity, new/worsen medical condition during pregnancy, fetal distress, abnormal labor, infant size for gestational age ≥ 50th percentiles, and self-pay for delivery fees. Women with existing blood conditions were less likely to have cesarean delivery.

CONCLUSIONS

Almost one in two pregnancies among women in our cohorts resulted in cesarean deliveries. Compared to WHO guidelines, cesarean delivery rates were elevated in selected Robson groups indicating that tailored interventions to minimize non-clinically indicated cesarean delivery for specific groups of pregnancies may be warranted.

Racial and ethnic disparities in influenza vaccination coverage among pregnant women in the United States: The contribution of vaccine-related attitudes

OBJECTIVE

Racial and ethnic disparities in influenza vaccination coverage among pregnant women in the United States have been documented. This study assessed the contribution of vaccine-related attitudes to coverage disparities.

METHODS

Surveys were conducted following the 2019-2020 and 2020-2021 influenza seasons in a US research network. Using electronic health record data to identify pregnant women, random samples were selected for surveying; non-Hispanic Black women and influenza-unvaccinated women were oversampled. Regression-based decomposition analyses were used to assess the contribution of vaccine-related attitudes to racial and ethnic differences in influenza vaccination. Data were combined across survey years, and analyses were weighted and accounted for survey design.

RESULTS

Survey response rate was 41.2% (721 of 1748) for 2019-2020 and 39.3% (706 of 1798) for 2020-2021. Self-reported influenza vaccination was higher among non-Hispanic White respondents (79.4% coverage, 95% CI 73.1%-85.7%) than Hispanic (66.2% coverage, 95% CI 52.5%-79.9%) and non-Hispanic Black (55.8% coverage, 95% CI 50.2%-61.4%) respondents. For all racial and ethnic groups, a high proportion (generally >80%) reported being seen for care, recommended for influenza vaccination, and offered vaccination. In decomposition analyses, vaccine-related attitudes (e.g., worry about vaccination causing influenza; concern about vaccine safety and effectiveness) explained a statistically significant portion of the observed racial and ethnic disparities in vaccination. Maternal age, education, and health status were not significant contributors after controlling for vaccine-related attitudes.

CONCLUSIONS

In a setting with relatively high influenza vaccination coverage among pregnant women, racial and ethnic disparities in coverage were identified. Vaccine-related attitudes were associated with the disparities observed.

Gender inequity and COVID-19 vaccination policies for pregnant women in the Americas

The region of the Americas has been the epicenter of the COVID-19 pandemic’s worst outcome in terms of number of deaths due to COVID-19. SARS-CoV-2 infection during pregnancy and the postpartum period has been found to be associated with increased risk of mortality and severe disease. Several Latin American and Caribbean countries have disproportionally high maternal mortality rates due to COVID-19. Although this region achieved relatively high vaccination rates among the general adult population, there were differing restrictions regarding the vaccination of those who were pregnant. In a pandemic, policies reflect political priorities in responses to the threats posed to populations and play an important role in promoting gender equity. This paper reports the results of an ethical analysis of 45 national COVID-19 vaccination public policies from seven countries – Argentina, Brazil, Canada, Colombia, Mexico, Peru, and United States. The analysis drew on reproductive justice and feminist bioethics frameworks, paying close attention to whether and how gender and social and economic inequities were addressed. It found that exclusionary approaches in immunization policies which restricted access to vaccination during pregnancy were often justified on the basis of a lack of evidence about the effects of immunization of pregnant persons, and on the grounds of medical expertise, to the detriment of women’s autonomy and agency. As such these policies reiterate patriarchal moral understandings of women, pregnancy and motherhood. In practice, they counter human rights gender equity and equality principles, and became lethal, particularly to racialized women in Latin America. During an emerging lethal disease, policies and policy development must consider the intersection of oppressive structures to protect and guarantee rights of women, girls, and pregnant persons.

Effectiveness of Maternal Influenza Vaccination in Peru PRIME Cohort

Background

Few studies have examined influenza vaccine effectiveness (VE) among women during pregnancy in middle-income countries. We used data from a prospective cohort of women who were pregnant in Peru to estimate effectiveness of the 2018 Southern Hemisphere influenza vaccine.

Methods

Women at <28 weeks gestation were enrolled from 4 tertiary level hospitals in Lima, Peru at the start of the 2018 influenza season and followed until the end of their pregnancies. Participants had mid-turbinate nasal swabs collected and tested for influenza by reverse-transcription polymerase chain reaction (RT-PCR) with onset of ≥1 of myalgia, cough, runny nose or nasal congestion, sore throat, or difficulty breathing. Time-varying Cox proportional hazard regression models were used to estimate the risk of RT-PCR-confirmed influenza infection after adjusting for inverse probability treatment weight.

Results

We followed 1896 women for a median of 127 days (interquartile range [IQR], 86-174). Participants had a median age of 29 years (IQR, 24-34). Among the 1896 women, 49% were vaccinated with the 2018 influenza vaccine and 1039 (55%) developed influenza-like illness, 76 (7%) of whom had RT-PCR-confirmed influenza. Incidence rates of RT-PCR-confirmed influenza were 36.6 and 15.3 per 100 000 person-days among women who were unvaccinated and vaccinated, respectively. Adjusted influenza VE was 22% (95% confidence interval, -64.1% to 62.9%).

Conclusions

Participants vaccinated against influenza had more than 50% lower incidence of RT-PCR-confirmed influenza illness. Although the VE estimated through propensity weight-adjusted time-varying Cox regression did not reach statistical significance, our findings provide additional evidence about the value of maternal influenza vaccination in middle-income countries.

Biological Sex and Pregnancy Affect Influenza Pathogenesis and Vaccination

Males and females differ in the outcome of influenza A virus (IAV) infections, which depends significantly on age. During seasonal influenza epidemics, young children (< 5 years of age) and aged adults (65+ years of age) are at greatest risk for severe disease, and among these age groups, males tend to suffer a worse outcome from IAV infection than females. Following infection with pandemic strains of IAVs, females of reproductive ages (i.e., 15-49 years of age) experience a worse outcome than their male counterparts. Although females of reproductive ages experience worse outcomes from IAV infection, females typically have greater immune responses to influenza vaccination as compared with males. Among females of reproductive ages, pregnancy is one factor linked to an increased risk of severe outcome of influenza. Small animal models of influenza virus infection and vaccination illustrate that immune responses and repair of damaged tissue following IAV infection also differ between the sexes and impact the outcome of infection. There is growing evidence that sex steroid hormones, including estrogens, progesterone, and testosterone, directly impact immune responses during IAV infection and vaccination. Greater consideration of the combined effects of sex and age as biological variables in epidemiological, clinical, and animal studies of influenza pathogenesis is needed.

Romiplostim use in pregnant women with immune thrombocytopenia

Treatment for immune thrombocytopenia (ITP) in pregnancy is hampered by the lack of fetal safety evidence of maternally-administered medications. The Pregnancy Surveillance Program (PSP) collected patient information from 2017-2020 for pregnancy, birth outcomes, and adverse events (AEs) for 186 women exposed to romiplostim from 20 days before pregnancy to the end of pregnancy. Timing of exposure was available in 128 women. Seventy-one mothers (38%) had prepregnancy exposure to romiplostim; intrapartum exposure was known for the first (for many mothers when they discovered their pregnancy), second, and third trimesters for 74 (40%), 22 (12%), and 44 (24%) mothers, respectively, with 15 mothers exposed during >1 trimester. Among the 86 mothers with known pregnancy outcomes, 46 (53%) had at least one pregnancy-related serious AE (SAE); approximately 2/3 of SAEs were due to underlying ITP. Of 92 mothers with known birth outcomes, 60 (65%) had a normal pregnancy and 16 (17%) had complications, with both categories including term and preterm births; there were 12 (14%) spontaneous miscarriages/stillbirths, 3 (3%) ectopic pregnancies, and 1 (1%) molar pregnancy. Most abnormal births resulted from abnormal pregnancies. There were five neonatal/postnatal AEs of note: inguinal hernia, cytomegalovirus infection, trisomy 8 (third trimester single-dose romiplostim exposure), single umbilical artery without known anomalies, and development of autism at age 2 years. Seven of 12 infants with neonatal thrombocytopenia had resolution of thrombocytopenia before discharge; all 12 were discharged. Review of pregnancies in women exposed to romiplostim did not reveal any specific safety concerns for mothers, fetuses, or infants.

Protecting pregnant people & infants against influenza: A landscape review of influenza vaccine hesitancy during pregnancy and strategies for vaccine promotion

Before COVID-19, influenza vaccines were the most widely recommended vaccine during pregnancy worldwide. In response to immunization during pregnancy, maternal antibodies offer protection against potentially life-threatening disease in both pregnant people and their infants up to six months of age. Despite this, influenza vaccine hesitancy is common, with few countries reporting immunization rates in pregnant people above 50%. In this review, we highlight individual, institutional, and social factors associated with influenza vaccine hesitancy during pregnancy. In addition, we present an overview of the evidence evaluating interventions to address influenza vaccine hesitancy during pregnancy. While some studies have indicated promising results, no single intervention has consistently effectively increased influenza vaccine uptake during pregnancy. Using a social-ecological model of health framework, future strategies addressing multiple levels of vaccine hesitancy will be needed to realize the potential health benefits of prenatal immunization programs.

Multisite surveillance for influenza and other respiratory viruses in India: 2016-2018

There is limited surveillance and laboratory capacity for non-influenza respiratory viruses in India. We leveraged the influenza sentinel surveillance of India to detect other respiratory viruses among patients with acute respiratory infection. Six centers representing different geographic areas of India weekly enrolled a convenience sample of 5-10 patients with acute respiratory infection (ARI) and severe acute respiratory infection (SARI) between September 2016-December 2018. Staff collected nasal and throat specimens in viral transport medium and tested for influenza virus, respiratory syncytial virus (RSV), parainfluenza virus (PIV), human meta-pneumovirus (HMPV), adenovirus (AdV) and human rhinovirus (HRV) by reverse transcription polymerase chain reaction (RT-PCR). Phylogenetic analysis of influenza and RSV was done. We enrolled 16,338 including 8,947 ARI and 7,391 SARI cases during the study period. Median age was 14.6 years (IQR:4-32) in ARI cases and 13 years (IQR:1.3-55) in SARI cases. We detected respiratory viruses in 33.3% (2,981) of ARI and 33.4% (2,468) of SARI cases. Multiple viruses were co-detected in 2.8% (458/16,338) specimens. Among ARI cases influenza (15.4%) were the most frequently detected viruses followed by HRV (6.2%), RSV (5%), HMPV (3.4%), PIV (3.3%) and AdV (3.1%),. Similarly among SARI cases, influenza (12.7%) were most frequently detected followed by RSV (8.2%), HRV (6.1%), PIV (4%), HMPV (2.6%) and AdV (2.1%). Our study demonstrated the feasibility of expanding influenza surveillance systems for surveillance of other respiratory viruses in India. Influenza was the most detected virus among ARI and SARI cases.

Maternal vaccination: A narrative review

Background

Vaccinations in general are considered to be one of the greatest achievements in medicine, saving millions of lives globally.

Aim

This narrative review highlights issues related to vaccination in pregnancy and provides information on those vaccines registered for use in pregnancy.

Method

Published articles on vaccinations in pregnancy are included in this review. The search engines used included PubMed, Medline, Google Scholar, and ScienceDirect.

Results

Vaccinations during pregnancy are more likely to be administered in high income countries (HICs) compared to low-income countries (LICs) due to easier access to healthcare services and better communicable disease awareness. Maternal and perinatal morbidity and mortality rates associated with infectious diseases are higher in LICs with access to maternal care services, infrastructure and hospital equipment lacking in these settings.

Conclusion

Suitable vaccinations are recommended for use in pregnancy to prevent harm to women, their foetuses and newborns from some communicable diseases, and they have resulted in declines in maternal and infant morbidity and mortality. Furthermore, this review has shown that vaccination during pregnancy is not only safe for both the woman and her foetus but also effective. Therefore, health professionals and national governments should strongly consider approved vaccinations prior to or during pregnancy.

Contribution

This review provides insight on the necessity of vaccination during pregnancy. In addition, it urges health professionals to inform patients of the importance of regular antenatal visits, and to receive the required vaccinations for a better health outcome.

Obstetric risk in pregnancy interacts with hair cortisone levels to reduce gestational length

Background

Maternal psychological stress has been linked to preterm birth. However, the differential contribution of psychological stress versus stress hormones is not clear. Studies focus primarily on perceived stress and cortisol, with few assessing its inter-convertible hormone cortisone. Furthermore, little is known about the potential moderating roles of obstetric risk and fetal sex in the relationship between maternal stress and gestational length. This gap in knowledge is particularly evident for rural women who typically experience chronic multiple stressors during pregnancy. We explored the relationship of hormonal and psychological stress to gestational length and the effects of obstetric risks and fetal sex on this relationship among Kenyan pregnant women.

Methods

The sample included 130 women recruited between 22 to 28 weeks gestation. They completed a clinical and sociodemographic questionnaire together with the Perceived Stress Scale and provided a hair sample for cortisol and cortisone assay. Women underwent an ultrasound to assess weeks of gestation. At delivery, their pregnancy-related health problems were identified using information extracted from medical records to compile each woman's number of pregnancy risks on the Obstetric Medical Risk Index (OMRI).

Results

Perceived stress and hair cortisol were not significant predictors of gestational length. However, a greater number of obstetric risks on the OMRI was associated with shorter gestational length. This effect was further explained by the interaction between obstetric risk and hair cortisone (B = 0.709, p = 0.02). Hair cortisone levels of mothers who had a shorter gestation were significantly higher in mothers with 2 or more risks on the OMRI but not among mothers with only one or no risks (t = 2.39, p = 0.02). Fetal sex had no relationship to gestational length and also had no moderating effect on the relationship between any stress-related metric and gestational length.

Conclusion

Cortisone levels may increase in anticipation of shorter gestation as a compensatory response to increased obstetric risk. Elevated cortisone may be a more sensitive marker of risk for early delivery than cortisol or psychological stress, with salience for both the male and female fetus.

Nonrespiratory sites of influenza-associated disease: mechanisms and experimental systems for continued study

The productive replication of human influenza viruses is almost exclusively restricted to cells in the respiratory tract. However, a key aspect of the host response to viral infection is the production of inflammatory cytokines and chemokines that are not similarly tissue restricted. As such, circulating inflammatory mediators, as well as the resulting activated immune cells, can induce damage throughout the body, particularly in individuals with underlying conditions. As a result, more holistic experimental approaches are required to fully understand the pathogenesis and scope of influenza virus-induced disease. This review summarizes what is known about some of the most well-appreciated nonrespiratory tract sites of influenza virus-induced disease, including neurological, cardiovascular, gastrointestinal, muscular and fetal developmental phenotypes. In the context of this discussion, we describe the in vivo experimental systems currently being used to study nonrespiratory symptoms. Finally, we highlight important future questions and potential models that can be used for a more complete understanding of influenza virus-induced disease.

Respiratory Syncytial Virus in Pregnant Women: Systematic Review and Meta-Analysis

Human Respiratory Syncytial Virus (RSV) is a highly contagious viral pathogen. In infants, it is usually listed among the main causes of medical referrals and hospitalizations, particularly among newborns. While waiting for the results of early randomized controlled trials on maternal vaccination against RSV, the present systematic review and meta-analysis aimed to collect available evidence on maternal RSV infections. According to the PRISMA statement, Pubmed, Embase, and pre-print archive medRxiv.og were searched for eligible studies published up to 1 April 2022. Raw data included the incidence of RSV infection among sampled pregnant women, and the occurrence of complications. Data were then pooled in a random-effects model. Heterogeneity was assessed using the I2 measure, while reporting bias was assessed by means of funnel plots and regression analysis. A total of 5 studies for 282,918 pregnancies were retrieved, with a pooled prevalence of 0.2 per 100 pregnancies and 2.5 per 100 pregnancies with respiratory tract infections. Neither maternal deaths nor miscarriages were reported. Even though detailed data were available only for 6309 pregnancies and 33 RSV cases, infant outcomes such as low birth weight and preterm delivery were rare (in both cases 0.04%), but up to 9.1% in cases where RSV diagnosis was confirmed. No substantially increased risk for preterm delivery (RR 1.395; 95%CI 0.566 to 3.434) and giving birth to a low-birth-weight infant (RR 0.509; 95%CI 0.134 to 1.924) was eventually identified. Conclusions. Although RSV is uncommonly detected among pregnant women, incident cases were associated with a relatively high share of complications. However, heterogeneous design and the quality of retrieved reports stress the need for specifically designed studies.

Recent Progress in Recombinant Influenza Vaccine Development Toward Heterosubtypic Immune Response

Flu, a viral infection caused by the influenza virus, is still a global public health concern with potential to cause seasonal epidemics and pandemics. Vaccination is considered the most effective protective strategy against the infection. However, given the high plasticity of the virus and the suboptimal immunogenicity of existing influenza vaccines, scientists are moving toward the development of universal vaccines. An important property of universal vaccines is their ability to induce heterosubtypic immunity, i.e., a wide immune response coverage toward different influenza subtypes. With the increasing number of studies and mounting evidence on the safety and efficacy of recombinant influenza vaccines (RIVs), they have been proposed as promising platforms for the development of universal vaccines. This review highlights the current progress and advances in the development of RIVs in the context of heterosubtypic immunity induction toward universal vaccine production. In particular, this review discussed existing knowledge on influenza and vaccine development, current hemagglutinin-based RIVs in the market and in the pipeline, other potential vaccine targets for RIVs (neuraminidase, matrix 1 and 2, nucleoprotein, polymerase acidic, and basic 1 and 2 antigens), and deantigenization process. This review also provided discussion points and future perspectives in looking at RIVs as potential universal vaccine candidates for influenza.

Trends of influenza vaccination coverage in pregnant women: a ten-year analysis from a French healthcare database

Pregnant women have a high risk of severe influenza, associated with obstetrical complications. The World Health Organization (WHO) has recommended influenza vaccination for all pregnant women since 2012. The vaccination coverage remains low worldwide, and in Europe, due to a lack of proposition from the health care providers, and a high refusal rate from the women. The primary aim of this study was to estimate the influenza vaccination coverage (IVC) in a population of pregnant women in France, and to analyse its evolution from 2009 to 2018. The secondary objective was to describe the vaccinated population and to find determinants associated with the vaccination. This retrospective cohort study is based on the EGB French health care database, a representative sample of the French population containing data from the health insurance system. All pregnant women who delivered medically or spontaneously over the 2009–2018 period were included. In the 2009–2018 period, only 1.2% pregnant women were vaccinated against influenza (n = 875/72,207; 95% CI 1.14–1.30). The IVC slightly increased after the 2012 WHO recommendation, from 0.33 to 1.79% (p < 0.001) but remained extremely low (4.1% in 2018). Women younger than 25 years old had a low coverage (0.6%) whereas women over 35 years old were more likely to get the influenza vaccine (1.7%; OR: 2.82, 95% CI 2.14–3.71). The vaccination behavior was not influenced by multifetal pregnancy or parity, but socio-economically deprived women were less likely to be vaccinated (OR: 0.81, 95% CI: 0.67–0.98). Women with pre-existing medical conditions had an overall higher vaccination rate (2.5%; OR: 2.32, 95% CI: 1.94–2.77). The vaccine was mainly prescribed by family physicians (58%). Influenza vaccination in pregnant women in France remains very low, particularly in younger, healthy women, and measures such as information campaigns towards pregnant women and studies of the knowledge, attitudes, and practices of the health care professionals need to be undertaken to improve the coverage.

RSV Prevention in All Infants: Which Is the Most Preferable Strategy?

Respiratory syncytial virus (RSV) causes a spectrum of respiratory illnesses in infants and young children that may lead to hospitalizations and a substantial number of outpatient visits, which result in a huge economic and healthcare burden. Most hospitalizations happen in otherwise healthy infants, highlighting the need to protect all infants against RSV. Moreover, there is evidence on the association between early-life RSV respiratory illness and recurrent wheezing/asthma-like symptoms As such, RSV is considered a global health priority. However, despite this, the only prevention strategy currently available is palivizumab, a monoclonal antibody (mAb) indicated in a subset of preterm infants or those with comorbidities, hence leaving the majority of the infant population unprotected against this virus. Therefore, development of prevention strategies against RSV for all infants entering their first RSV season constitutes a large unmet medical need. The aim of this review is to explore different immunization approaches to protect all infants against RSV. Prevention strategies include maternal immunization, immunization of infants with vaccines, immunization of infants with licensed mAbs (palivizumab), and immunization of infants with long-acting mAbs (e.g., nirsevimab, MK-1654). Of these, palivizumab use is restricted to a small population of infants and does not offer a solution for all-infant protection, whereas vaccine development in infants has encountered various challenges, including the immaturity of the infant immune system, highlighting that future pediatric vaccines will most likely be used in older infants (>6 months of age) and children. Consequently, maternal immunization and immunization of infants with long-acting mAbs represent the two feasible strategies for protection of all infants against RSV. Here, we present considerations regarding these two strategies covering key areas which include mechanism of action, "consistency" of protection, RSV variability, duration of protection, flexibility and optimal timing of immunization, benefit for the mother, programmatic implementation, and acceptance of each strategy by key stakeholders. We conclude that, based on current data, immunization of infants with long-acting mAbs might represent the most effective approach for protecting all infants entering their first RSV season.

Maternal vaccination: a review of current evidence and recommendations

Maternal vaccination is an effective means of protecting pregnant women, their fetuses, and infants from vaccine-preventable infections. Despite the availability of sufficient safety data to support the use of vaccines during pregnancy, maternal immunization remains an underutilized method of disease prevention, often because of concerns from both healthcare providers and pregnant women about vaccine safety. Such concerns have been reflected in the low uptake of the COVID-19 vaccine among pregnant women seen in many parts of the world. Here, we present an update of the current recommendations for the use of vaccines during pregnancy, including the evidence supporting the use of novel vaccine platforms. We also provide an overview of the data supporting the use of COVID-19 vaccines in pregnancy and an update of the status of vaccines that are currently under development for use in pregnant women.

Views and experiences of maternal healthcare providers regarding influenza vaccine during pregnancy globally: A systematic review and qualitative evidence synthesis

BACKGROUND

The World Health Organization (WHO) recommends that pregnant women receive influenza vaccination; however, uptake of the vaccine remains low. Maternity health care professionals (MHCPs) play an important role in motivating pregnant women to receive the influenza vaccine. However, factors such as MHCPs' views and knowledge about the vaccine, and time constraints due to workload may influence MHCPs' practices and opinions about women receiving the influenza vaccine during pregnancy. To date, the qualitative evidence exploring MHCPs' views and experiences around influenza vaccine uptake in pregnant women has not been synthesised.

AIM

To systematically review and thematically synthesise qualitative evidence that explores the views and experiences of MHCPs involved in the provision of the maternal influenza vaccine worldwide.

METHODS

Five databases (MEDLINE, EMBASE, PsycINFO, CINAHL, Web of Science) were searched, supplemented with searches of included paper reference lists and grey literature. Study selection was conducted by up to three researchers applying pre-specified inclusion/exclusion criteria. Quality assessment was undertaken, data were extracted, coded and synthesised to develop descriptive and analytical themes.

RESULTS

Eight studies involving 277 participants were included. Seventeen descriptive themes were interpreted, embedded within six analytical themes. MHCPs perceived that maternal influenza vaccination delivery can be facilitated by trusting relationships, good communication, knowledge about the vaccine leading to confidence in recommending vaccine, electronic vaccination prompts, and presence of national guidelines. However, workload, time constraints, MHCP's perception of pregnant women's concerns, and social/cultural/environmental influences could prevent the likelihood of delivery of influenza vaccine. Knowledgeable MHCPs who were regularly updated about vaccination based on scientific evidence were more confident when discussing and recommending the influenza vaccine to pregnant women. In addition, the presence of national policies and guidelines and electronic prompts for maternal influenza vaccination would enhance the delivery of the vaccine.

CONCLUSION

Our findings suggest that approaches to enhance the vaccination uptake rate in pregnant women include addressing MHCPs barriers to discussing influenza vaccination through education, sufficient time for discussions, and electronic prompts about vaccination, as well as evidence based local and national guidelines.

Characteristics and Outcomes of Hospitalized Pregnant Women With Influenza, 2010 to 2019 : A Repeated Cross-Sectional Study

BACKGROUND

Pregnant women may be at increased risk for severe influenza-associated outcomes.

OBJECTIVE

To describe characteristics and outcomes of hospitalized pregnant women with influenza.

DESIGN

Repeated cross-sectional study.

SETTING

The population-based U.S. Influenza Hospitalization Surveillance Network during the 2010-2011 through 2018-2019 influenza seasons.

PATIENTS

Pregnant women (aged 15 to 44 years) hospitalized with laboratory-confirmed influenza identified through provider-initiated or facility-based testing practices.

MEASUREMENTS

Clinical characteristics, interventions, and in-hospital maternal and fetal outcomes were obtained through medical chart abstraction. Multivariable logistic regression was used to evaluate the association between influenza A subtype and severe maternal influenza-associated outcomes, including intensive care unit (ICU) admission, mechanical ventilation, extracorporeal membrane oxygenation, or in-hospital death.

RESULTS

Of 9652 women aged 15 to 44 years and hospitalized with influenza, 2690 (27.9%) were pregnant. Among the 2690 pregnant women, the median age was 28 years, 62% were in their third trimester, and 42% had at least 1 underlying condition. Overall, 32% were vaccinated against influenza and 88% received antiviral treatment. Five percent required ICU admission, 2% required mechanical ventilation, and 0.3% (n = 8) died. Pregnant women with influenza A H1N1 were more likely to have severe outcomes than those with influenza A H3N2 (adjusted risk ratio, 1.9 [95% CI, 1.3 to 2.8]). Most women (71%) were still pregnant at hospital discharge. Among 754 women who were no longer pregnant at discharge, 96% had a pregnancy resulting in live birth, and 3% experienced fetal loss.

LIMITATION

Maternal and fetal outcomes that occurred after hospital discharge were not captured.

CONCLUSION

Over 9 influenza seasons, one third of reproductive-aged women hospitalized with influenza were pregnant. Influenza A H1N1 was associated with more severe maternal outcomes. Pregnant women remain a high-priority target group for vaccination.

PRIMARY FUNDING SOURCE

Centers for Disease Control and Prevention.

From maternal breath to infant's cells: Impact of maternal respiratory infections on infants 'immune responses

In utero exposure to maternally-derived antigens following chronic infection is associated with modulation of infants 'immune response, differential susceptibility to post-natal infections and immune response toward vaccines. The maternal environment, both internal (microbiota) and external (exposure to environmental microbes) also modulates infant's immune response but also the clinical phenotype after birth. Vertical transmission of ubiquitous respiratory pathogens such as influenza and COVID-19 is uncommon. Evidence suggest that in utero exposure to maternal influenza and SARS-CoV-2 infections may have a significant impact on the developing immune system with activation of both innate and adaptive responses, possibly related to placental inflammation. Here in, we review how maternal respiratory infections, associated with airway, systemic and placental inflammation but also changes in maternal microbiota might impact infant's immune responses after birth. The clinical impact of immune modifications observed following maternal respiratory infections remains unexplored. Given the high frequencies of respiratory infections during pregnancy (COVID-19, influenza but also RSV and HMPV), the impact on global child health could be important.

Cost-effectiveness of seasonal influenza vaccination in pregnant women, healthcare workers and adults >= 60 years of age in Lao People's Democratic Republic

BACKGROUND

Pregnant women, healthcare workers (HW), and adults >= 60 years have shown an increased vulnerability to seasonal influenza virus infections and/or complications. In 2012, the Lao People's Democratic Republic (Lao PDR) initiated a national influenza vaccination program for these target groups. A cost-effectiveness evaluation of this program was undertaken to inform program sustainability.

METHODS

We designed a decision-analytical model and collected influenza-related medical resource utilization and cost data, including indirect costs. Model inputs were obtained from medical record abstraction, interviews of patients and staff at hospitals in the national influenza sentinel surveillance system and/or from literature reviews. We compared the annual disease and economic impact of influenza illnesses in each of the target groups in Lao PDR under scenarios of no vaccination and vaccination, and then estimated the cost-effectiveness of the vaccination program. We performed sensitivity analyses to identify influential variables.

RESULTS

Overall, the vaccination of pregnant women, HWs, and adults >= 60 years could annually save 11,474 doctor visits, 1,961 days of hospitalizations, 43,027 days of work, and 1,416 life-years due to laboratory-confirmed influenza illness. After comparing the total vaccination program costs of 23.4 billion Kip, to the 18.4 billion Kip saved through vaccination, we estimated the vaccination program to incur a net cost of five billion Kip (599,391 USD) annually. The incremental cost per life-year saved (ICER) was 44 million Kip (5,295 USD) and 6.9 million Kip (825 USD) for pregnant women and adults >= 60 years, respectively. However, vaccinating HWs provided societal cost-savings, returning 2.88 Kip for every single Kip invested. Influenza vaccine effectiveness, attack rate and illness duration were the most influential variables to the model.

CONCLUSION

Providing influenza vaccination to HWs in Lao PDR is cost-saving while vaccinating pregnant women and adults >= 60 is cost-effective and highly cost-effective, respectively, per WHO standards.

Incidence of influenza and other respiratory viruses among pregnant women; a multi-country, multiyear cohort

OBJECTIVE

To quantify rates of influenza illness and assess value of influenza vaccination among pregnant women in Panama and El Salvador.

METHODS

Pregnant women were enrolled and followed each week in a prospective cohort study to identify acute respiratory infections (ARI). Nasopharyngeal swabs obtained from women with febrile ARI were tested by reverse-transcription polymerase chain reaction for influenza and other respiratory viruses.

RESULTS

We enrolled 2,556 women between October 2014-April 2017. Sixteen percent developed at least one ARI; 59 had two ARI, and five had three ARI for a total of 463 ARI. Women in El Salvador and Panama contributed 297 person-years (py) and 293py, respectively, during influenza circulation. Twenty-one (11%) of 196 sampled women tested positive for influenza. Influenza incidence was 5.0/100py (4.3/100py in Panama and 5.7/100py in El Salvador). Only 13% of women in El Salvador and 43% in Panama had been vaccinated against influenza before influenza epidemics (p<0.0001).

CONCLUSIONS

One in six pregnant women developed ARI and more than one in ten ARI were attributable to vaccine-preventable influenza. While women were at risk of influenza, few had vaccinated before each epidemic. Such findings suggest the utility of evaluations to optimize vaccine timing and coverage.

History of pandemic H1N1-containing influenza vaccination and risk for spontaneous abortion and birth defects

BACKGROUND

One recent study suggested an association between receipt of pandemic H1N1 (pH1N1)-containing vaccines in consecutive influenza seasons and spontaneous abortion, but corroborating scientific evidence is limited. In the present study, we leveraged a population of vaccine-compliant pregnant military women to examine history of pH1N1-containing influenza vaccination and adverse pregnancy outcomes. Because seasonal influenza vaccination is compulsory for military service, safety concerns regarding repeat vaccination are particularly relevant in this population.

METHODS

Pregnancies and live births from Department of Defense Birth and Infant Health Research program data were linked with military personnel immunization records to identify women vaccinated with a pH1N1-containing vaccine in pregnancy prior to 21 6/7 weeks' gestation, October 2009-April 2015. Cox and modified Poisson regression models estimated associations between vaccination with pH1N1- versus non-pH1N1-containing influenza vaccine in the season prior to the index pregnancy, and spontaneous abortion and birth defects, respectively. Cox models were calculated for two periods of follow-up: through (1) 21 6/7 weeks' gestation and (2) 28 days postvaccination.

RESULTS

Of 26,264 pregnancies, 21,736 (82.8%) were among women who received a dose of pH1N1-containing vaccine in the prior influenza season and 4,528 (17.2%) were among women who received non-pH1N1-containing vaccine in the prior influenza season. Among 23,121 infants, 19,365 (83.8%) and 3,756 (16.2%) had mothers exposed and unexposed to pH1N1-containing vaccine in the prior influenza season, respectively. The adjusted hazard ratio (aHR) for spontaneous abortion approximated 1.0 across the complete follow-up period (95% confidence interval [CI]: 0.89-1.13) and was slightly elevated when censored at 28 days postvaccination, though the CI was imprecise (aHR: 1.19; 95% CI: 0.97-1.46). No associations with birth defects were observed.

CONCLUSION

This work lends additional safety evidence and support for vaccination against pH1N1 in pregnancy, regardless of the vaccine received in the prior influenza season.

Feasibility and Performance of Self-Collected Nasal Swabs for Detection of Influenza Virus, Respiratory Syncytial Virus, and Human Metapneumovirus

BACKGROUND

We assessed performance of participant-collected midturbinate nasal swabs compared to study staff-collected midturbinate nasal swabs for the detection of respiratory viruses among pregnant women in Bangkok, Thailand.

METHODS

We enrolled pregnant women aged ≥18 years and followed them throughout the 2018 influenza season. Women with acute respiratory illness self-collected midturbinate nasal swabs at home for influenza viruses, respiratory syncytial viruses (RSV), and human metapneumoviruses (hMPV) real-time RT-PCR testing and the study nurse collected a second midturbinate nasal swab during home visits. Paired specimens were processed and tested on the same day.

RESULTS

The majority (109, 60%) of 182 participants were 20-30 years old. All 200 paired swabs had optimal specimen quality. The median time from symptom onsets to participant-collected swabs was 2 days and to staff-collected swabs was also 2 days. The median time interval between the 2 swabs was 2 hours. Compared to staff-collected swabs, the participant-collected swabs were 93% sensitive and 99% specific for influenza virus detection, 94% sensitive and 99% specific for RSV detection, and 100% sensitive and 100% specific for hMPV detection.

CONCLUSIONS

Participant-collected midturbinate nasal swabs were a valid alternative approach for laboratory confirmation of influenza-, RSV-, and hMPV-associated illnesses among pregnant women in a community setting.

Perinatal Outcomes of Asynchronous Influenza Vaccination, Ceará, Brazil, 2013-2018

In Ceará, Brazil, seasonal influenza transmission begins before national annual vaccination campaigns commence. To assess the perinatal consequences of this misalignment, we tracked severe acute respiratory infection (SARI), influenza, and influenza immunizations during 2013-2018. Among 3,297 SARI cases, 145 (4.4%) occurred in pregnant women. Statewide vaccination coverage was >80%; however, national vaccination campaigns began during or after peak influenza season. Thirty to forty weeks after peak influenza season, birthweights decreased by 40 g, and rates of prematurity increased from 10.7% to 15.5%. We identified 61 children born to mothers with SARI during pregnancy; they weighed 10% less at birth and were more likely to be premature than 122 newborn controls. Mistiming of influenza vaccination campaigns adversely effects perinatal outcomes in Ceará. Because Ceará is the presumptive starting point for north-to-south seasonal influenza transmission in Brazil, earlier national immunization campaigns would provide greater protection for pregnant women and their fetuses in Ceará and beyond.

Influenza Complicating Delivery Hospitalization and Its Association With Severe Maternal Morbidity in the United States, 2000-2018

OBJECTIVE

To characterize trends of an influenza diagnosis at delivery hospitalization and its association with severe maternal morbidity.

METHODS

We conducted a repeated cross-sectional analysis of delivery hospitalizations using the Nationwide Inpatient Sample from 2000 to 2018. We assessed the association between an influenza diagnosis at delivery hospitalization and severe maternal morbidity excluding transfusion per Centers for Disease Control and Prevention criteria. Secondary outcomes included maternal death and morbidity measures associated with influenza (mechanical intubation and ventilation, sepsis and shock, and acute respiratory distress syndrome [ARDS]) and obstetric complications (preterm birth and hypertensive disorders of pregnancy). We assessed trends of severe maternal morbidity by annual influenza season and the association between influenza and severe maternal morbidity using multivariable log-linear regression, adjusting for demographic, clinical, and hospital characteristics.

RESULTS

Of 74.7 million delivery hospitalizations, 23 per 10,000 were complicated by an influenza diagnosis. The rate of severe maternal morbidity was higher with an influenza diagnosis compared with those without influenza (86-410 cases vs 53-70 cases/10,000 delivery hospitalizations). Women with an influenza diagnosis at delivery hospitalization were at an increased risk of severe maternal morbidity compared with those without influenza (2.3 vs 0.7%; adjusted risk ratio 2.24, 95% CI 2.17-2.31). This association held for maternal death, mechanical intubation, sepsis and shock, and ARDS-as well as obstetric complications, including preterm birth and hypertensive disorders of pregnancy.

CONCLUSION

Pregnant women with influenza are at increased risk of severe maternal morbidity, as well as influenza-related maternal and obstetric complications. These results emphasize the importance of primary prevention and recognition of influenza infection during pregnancy to reduce downstream maternal morbidity and mortality.

Seasonal Influenza Prevention and Control Progress in Latin America and the Caribbean in the Context of the Global Influenza Strategy and the COVID-19 Pandemic

Each year in Latin America and the Caribbean, seasonal influenza is associated with an estimated 36,500 respiratory deaths and 400,000 hospitalizations. Since the 2009 influenza A(H1N1) pandemic, the Region has made significant advances in the prevention and control of seasonal influenza, including improved surveillance systems, burden estimates, and vaccination of at-risk groups. The Global Influenza Strategy 2019–2030 provides a framework to strengthen these advances. Against the backdrop of this new framework, the University of Colorado convened in October 2020 its Immunization Advisory Group of Experts to review and discuss current surveillance, prevention, and control strategies for seasonal influenza in Latin America and the Caribbean, also in the context of the COVID-19 pandemic. This review identified five areas for action and made recommendations specific to each area. The Region should continue its efforts to strengthen surveillance and impact evaluations. Existing data on disease burden, seasonality patterns, and vaccination effectiveness should be used to inform decision-making at the country level as well as advocacy efforts for programmatic resources. Regional and country strategic plans should be prepared and include specific targets for 2030. Existing investments in influenza prevention and control, including for immunization programs, should be optimized. Finally, regional partnerships, such as the regional networks for syndromic surveillance and vaccine effectiveness evaluation (SARInet and REVELAC-i), should continue to play a critical role in continuous learning and standardization by sharing experiences and best practices among countries.

Efficacy and safety of influenza vaccination during pregnancy: realizing the potential of maternal influenza immunization

Introduction: Pregnant women are at higher risk of severe complications following influenza infection compared to the general population. Influenza vaccination during pregnancy can offer direct protection to pregnant women and passive immunity to infants up to 6 months of age via maternal antibodies. Pregnant women are a high priority group for influenza immunization.Areas covered: This review provides an overview of the basis for recommending influenza vaccine to pregnant women, current immunization policies, the evidence supporting the safety and effectiveness of maternal vaccination, and future research needed. We conducted a search of PubMed for articles describing the safety or efficacy of influenza vaccines administered during pregnancy. Published articles from inception to 17 November 2020 were reviewed.Expert opinion: Experimental and observational evidence support the efficacy, effectiveness and safety of influenza immunization during pregnancy. These data support the continued provision of inactivated influenza vaccine to pregnant women, as recommended by global immunization policies. To achieve success with maternal influenza immunization programs, further work is needed to inform policy development in low- and middle-income settings and implementation and promotion in high-income settings.

The effect of influenza virus infection on pregnancy outcomes: A systematic review and meta-analysis of cohort studies

BACKGROUND

Adverse pregnancy outcomes are risk factors for neonatal mortality and morbidity. While some studies have demonstrated notable associations between influenza and adverse pregnancy outcomes, the findings have contrasted with other studies. This meta-analysis was conducted to assess the effect of influenza infection on pregnancy outcomes.

METHODS

We searched PubMed, Embase, Cochrane Library and Web of Science from inception to 4 November 2020. Relative risks (RRs) with 95% confidence intervals (CIs) were pooled using random-effects or fixed-effects models.

RESULTS

A total of 17 studies involving 2,351,204 participants were included. Influenza infection increased the risk of stillbirth (RR = 3.62, 95% CI: 1.60-8.20), with no significant effect on preterm birth (RR = 1.17, 95%CI: 0.95-1.45), fetal death (RR = 0.93, 95%CI: 0.73-1.18), small for gestational age (SGA) (RR = 1.10, 95%CI: 0.98-1.24) and low birth weight (LBW) (RR = 1.88, 95%CI: 0.46-7.66). In a subgroup analysis of LBW, the association was evident in studies conducted during the 2009 H1N1 pandemic (RR = 2.28, 95%CI: 1.81-2.87), with no evidence of an association in pre-pandemic or post-pandemic studies.

CONCLUSIONS

Influenza virus infection was associated with an increased risk of stillbirth, but its effect on preterm birth, fetal death, SGA and LBW is still uncertain.