Maternal Effects of Respiratory Syncytial Virus Infection during Pregnancy

Characteristics and Outcomes of Pregnant Women Hospitalized With Laboratory-Confirmed Respiratory Syncytial Virus Before and During the COVID-19 Pandemic

Background

Respiratory syncytial virus (RSV) can cause severe disease among infants and older adults. Less is known about RSV among pregnant women.

Methods

To analyze hospitalizations with laboratory-confirmed RSV among women aged 18 to 49 years, we used data from the RSV Hospitalization Surveillance Network (RSV-NET), a multistate population-based surveillance system. Specifically, we compared characteristics and outcomes among (1) pregnant and nonpregnant women during the pre-COVID-19 pandemic period (2014-2018), (2) pregnant women with respiratory symptoms during the prepandemic and pandemic periods (2021-2023), and (3) pregnant women with and without respiratory symptoms in the pandemic period. Using multivariable logistic regression, we examined whether pregnancy was a risk factor for severe outcomes (intensive care unit admission or in-hospital death) among women aged 18 to 49 years who were hospitalized with RSV prepandemic.

Results

Prepandemic, 387 women aged 18 to 49 years were hospitalized with RSV. Of those, 350 (90.4%) had respiratory symptoms, among whom 33 (9.4%) were pregnant. Five (15.2%) pregnant women and 74 (23.3%) nonpregnant women were admitted to the intensive care unit; no pregnant women and 5 (1.6%) nonpregnant women died. Among 279 hospitalized pregnant women, 41 were identified prepandemic and 238 during the pandemic: 80.5% and 35.3% had respiratory symptoms, respectively (P < .001). Pregnant women were more likely to deliver during their RSV-associated hospitalization during the pandemic vs the prepandemic period (73.1% vs 43.9%, P < .001).

Conclusions

Few pregnant women had severe RSV disease, and pregnancy was not a risk factor for a severe outcome. More asymptomatic pregnant women were identified during the pandemic, likely due to changes in testing practices for RSV.

Society for Maternal-Fetal Medicine Statement: Clinical considerations for the prevention of respiratory syncytial virus disease in infants

Respiratory syncytial virus is a leading cause of lower respiratory tract illness globally in children aged <5 years. Each year, approximately 58,000 hospitalizations in the United States are attributed to respiratory syncytial virus. Infants aged ≤6 months experience the most severe morbidity and mortality. Until recently, prevention with the monoclonal antibody, palivizumab, was only offered to infants with high-risk conditions, and treatment primarily consisted of supportive care. Currently, 2 products are approved for the prevention of respiratory syncytial virus in infants. These include the Pfizer bivalent recombinant respiratory syncytial virus prefusion F protein subunit vaccine, administered seasonally to the pregnant person between 32 0/7 and 36 6/7 weeks of gestation, and the monoclonal antibody, nirsevimab, administered to infants aged up to 8 months entering their first respiratory syncytial virus season. With few exceptions, administering both the vaccine to the pregnant person and the monoclonal antibody to the infant is not recommended. All infants should be protected against respiratory syncytial virus using one of these strategies. Key considerations for pregnant individuals include examining available safety and efficacy data, weighing accessibility and availability, and patient preferences for maternal vaccination vs infant monoclonal antibody treatment. It will be critical for maternal-fetal medicine physicians to provide effective and balanced counseling to aid patients in deciding on a personalized approach to the prevention of respiratory syncytial virus in their infants.

Impact of respiratory viral infections during pregnancy on the neurological outcomes of the newborn: current knowledge

Brain development is a complex process that begins during pregnancy, and the events occurring during this sensitive period can affect the offspring's neurodevelopmental outcomes. Respiratory viral infections are frequently reported in pregnant women, and, in the last few decades, they have been related to numerous neuropsychiatric sequelae. Respiratory viruses can disrupt brain development by directly invading the fetal circulation through vertical transmission or inducing neuroinflammation through the maternal immune activation and production of inflammatory cytokines. Influenza virus gestational infection has been consistently associated with psychotic disorders, such as schizophrenia and autism spectrum disorder, while the recent pandemic raised some concerns regarding the effects of severe acute respiratory syndrome coronavirus 2 on neurodevelopmental outcomes of children born to affected mothers. In addition, emerging evidence supports the possible role of respiratory syncytial virus infection as a risk factor for adverse neuropsychiatric consequences. Understanding the mechanisms underlying developmental dysfunction allows for improving preventive strategies, early diagnosis, and prompt interventions.

Burden of disease of respiratory syncytial virus in infants, young children and pregnant women and people

Background

Passive immunization products for infants and pregnant women and people have sparked interest in understanding Canada's respiratory syncytial virus (RSV) burden. This rapid review examines RSV burden of disease in infants, young children and pregnant women and people.

Methods

Electronic databases were searched to identify studies and systematic reviews reporting data on outpatient visits, hospitalizations, intensive care unit admissions, deaths and preterm labour associated with RSV. We also contacted Canadian respiratory virus surveillance experts for additional data.

Results

Overall, 17 studies on infants and young children and 10 studies on pregnant women and people were included, in addition to primary surveillance data from one Canadian territory (Yukon). There were higher rates of medical utilization for infants than older children. Hospitalization rates were highest in infants under six months (more than 1% annually), with 5% needing intensive care unit admission, but mortality was low. Severe outcomes often occurred in healthy full-term infants and burden was higher than influenza. Respiratory syncytial virus attack rate was 10%-13% among pregnant women and people. Only one study found a higher hospitalization rate in pregnant women and people compared to non-pregnant women and people. Limited evidence was found on intensive care unit admission, death and preterm birth for pregnant women and people.

Conclusion

While risk of severe outcomes is larger in high-risk infants and children, healthcare burden is greatest in healthy term infants. The RSV severity for pregnant women and people appears to be similar to that for non-pregnant women and people.

Respiratory Syncytial Virus-An Update for Prenatal and Primary Health Providers

Respiratory syncytial virus (RSV) infection is a significant cause of morbidity and mortality among infants aged younger than 1 year, adults aged 65 years or older, and immunocompromised persons. Limited data exist on RSV infection in pregnancy and further research is needed. Strides are being made to develop vaccines, including vaccines for maternal immunization, as well as monoclonal antibodies for disease prevention.

Maternal exposure to ultrafine particles enhances influenza infection during pregnancy

BACKGROUND

Interactions between air pollution and infectious agents are increasingly recognized and critical to identify, especially to protect vulnerable populations. Pregnancy represents a vulnerable period for influenza infection and air pollution exposure, yet interactions during pregnancy remain unclear. Maternal exposure to ultrafine particles (UFPs, [Formula: see text] 100 nm diameter), a class of particulate matter ubiquitous in urban environments, elicits unique pulmonary immune responses. We hypothesized that UFP exposure during pregnancy would lead to aberrant immune responses to influenza enhancing infection severity.

RESULTS

Building from our well-characterized C57Bl/6N mouse model employing daily gestational UFP exposure from gestational day (GD) 0.5-13.5, we carried out a pilot study wherein pregnant dams were subsequently infected with Influenza A/Puerto Rico/8/1934 (PR8) on GD14.5. Findings indicate that PR8 infection caused decreased weight gain in filtered air (FA) and UFP-exposed groups. Co-exposure to UFPs and viral infection led to pronounced elevation in PR8 viral titer and reduced pulmonary inflammation, signifying potential suppression of innate and adaptive immune defenses. Pulmonary expression of the pro-viral factor sphingosine kinase 1 (Sphk1) and pro-inflammatory cytokine interleukin-1β (IL-1 [Formula: see text]) was significantly increased in pregnant mice exposed to UFPs and infected with PR8; expression correlated with higher viral titer.

CONCLUSIONS

Results from our model provide initial insight into how maternal UFP exposure during pregnancy enhances respiratory viral infection risk. This model is an important first step in establishing future regulatory and clinical strategies for protecting pregnant women exposed to UFPs.

Responding to Higher-Than-Expected Infant Mortality Rates from Respiratory Syncytial Virus (RSV): Improving Treatment and Reporting Strategies

Respiratory syncytial virus (RSV) has a major role in respiratory infections in young infants around the world. However, substantial progress has been made in recent years in the field of RSV. A wide variety of observational studies and clinical trials published in the past decade provide a thorough idea of the health and economic burden of RSV disease in the developing world. In this review, we discuss the impact of RSV burden of disease, major gaps in disease estimations, and challenges in generating new therapeutic options and an immune response against the virus, and briefly describe next generation technologies that are being evaluated.

RSV disease in infants and young children: Can we see a brighter future?

Respiratory syncytial virus (RSV) is a highly contagious seasonal virus and the leading cause of Lower Respiratory Tract Infections (LRTI), including pneumonia and bronchiolitis in children. RSV-related LRTI cause approximately 3 million hospitalizations and 120,000 deaths annually among children <5 years of age. The majority of the burden of RSV occurs in previously healthy infants. Only a monoclonal antibody (mAb) has been approved against RSV infections in a restricted group, leaving an urgent unmet need for a large number of children potentially benefiting from preventive measures. Approaches under development include maternal vaccines to protect newborns, extended half-life monoclonal antibodies to provide rapid long-lasting protection, and pediatric vaccines. RSV has been identified as a major global priority but a solution to tackle this unmet need for all children has yet to be implemented. New technologies represent the avenue for effectively addressing the leading-cause of hospitalization in children <1 years old.

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.

Potential Neurocognitive Symptoms Due to Respiratory Syncytial Virus Infection

Respiratory infections are among the major public health burdens, especially during winter. Along these lines, the human respiratory syncytial virus (hRSV) is the principal viral agent causing acute lower respiratory tract infections leading to hospitalization. The pulmonary manifestations due to hRSV infection are bronchiolitis and pneumonia, where the population most affected are infants and the elderly. However, recent evidence suggests that hRSV infection can impact the mother and fetus during pregnancy. Studies have indicated that hRSV can infect different cell types from the placenta and even cross the placenta barrier and infect the fetus. In addition, it is known that infections during the gestational period can lead to severe consequences for the development of the fetus due not only to a direct viral infection but also because of maternal immune activation (MIA). Furthermore, it has been described that the development of the central nervous system (CNS) of the fetus can be affected by the inflammatory environment of the uterus caused by viral infections. Increasing evidence supports the notion that hRSV could invade the CNS and infect nervous cells, such as microglia, neurons, and astrocytes, promoting neuroinflammation. Moreover, it has been described that the hRSV infection can provoke neurological manifestations, including cognitive impairment and behavioral alterations. Here, we will review the potential effect of hRSV in brain development and the potential long-term neurological sequelae.

Maternal RSV vaccine development. Where to from here?

Respiratory syncytial virus (RSV) is a common cause of acute lower respiratory tract infection and is responsible for a large proportion of infant morbidity and mortality worldwide. Most RSV-related deaths occur in children under six months, and the majority of these occur in low-income settings. To date, there is no known efficacious treatment for RSV infection; hence, prevention remains an important strategy to reduce the global burden of disease. Monoclonal antibodies and vaccinations are currently the two main approaches for prevention of RSV disease. Maternal RSV vaccination is of particular interest as a strategy to protect infants during their most vulnerable period as this approach has proven highly efficacious in other vaccine-preventable conditions such as pertussis and influenza. As results from ongoing phase III clinical trials become available, important decisions will need to be made about the priority and potential implementation of RSV vaccines alongside other public health measures.

In silico virtual screening of lead compounds for major antigenic sites in respiratory syncytial virus fusion protein

Human respiratory syncytial virus (RSV) is a leading ubiquitous respiratory pathogen in newborn infants, young children, and the elderly, with no vaccine available to date. The viral fusion glycoprotein (RSV F) plays an essential role in the infection process, and it is a primary target of neutralizing antibodies, making it an attractive site for vaccine development. With this in view, there is a persistent need to identify selective antiviral drugs against RSV, targeting the major antigenic sites on the F protein. We aimed to conduct a robust in silico high-throughput drug screening of one million compounds to explore potential inhibitors that bind the major antigenic site Ø and site II on RSV F protein, which are the main target of neutralizing antibodies (NAb). We utilized the three-dimensional crystallographic structure of both antigenic site Ø on pre-F and antigenic II on post-F to screen for potential anti-RSV inhibitors. A library of one million small compounds was docked to explore lead binders in the major antigenic sites by using virtual lab bench CLC Drug Discovery. We also performed Quantitative Structure-Activity and Relationship (QSAR) for the lead best binders known for their antiviral activity. Among one million tested ligands, seven ligands (PubChem ID: 3714418, 24787350, 49828911, 24802036, 79824892, 49726463, and 3139884) were identified as the best binders to neutralizing epitopes site Ø and four ligands (PubChem ID: 865999, 17505357, 24802036, and 24285058) to neutralizing epitopes site II, respectively. These binders exhibited significant interactions with neutralizing epitopes on RSV F, with an average of six H bonds, docking energy of - 15.43 Kcal·mol^-1, and minimum interaction energy of - 7.45 Kcal·mol^-1. Using in silico virtual screening, we identified potential RSV inhibitors that bind two major antigenic sites on the RSV F protein. Using structure-based design and combination-based drug therapy, identified molecules could be modified to generate the next generation anti-RSV drugs.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s42247-021-00213-6.

Adverse Outcomes in Pregnant Women Hospitalized With Respiratory Syncytial Virus Infection: A Case Series

We identified 10 women hospitalized with respiratory syncytial virus infection during pregnancy. Diagnoses included pneumonia/atelectasis (5), respiratory failure (2), and sepsis (2). Six had obstetrical complications during hospitalization, including 1 induced preterm birth. One required intensive care unit admission and mechanical ventilation. Four infants had complications at birth.

Risk factor analysis for congenital heart defects in children

Congenital heart defects (CHDs) are the most common malformations, occurring in almost 1.0 in 100 births. We investigated an association between risk factors and CHDs, because epidemiological studies have reported conflicting results regarding risk factors and CHDs recently. The study of CHD frequency was conducted in Chernivtsi region (Northern Bukovina) on the basis of the medical genetic center. A retrospective method of research by studying registration genetic maps was used to analyze risk factors. 91 cards of infants suffering from CHD (47 boys and 44 girls) aged 0–1 living in the territory of Northern Bukovina were selected. In order to identify risk factors, 133 cards of healthy infants (77 boys and 56 girls) were used. The analysis of risk factors revealed that the female gender of a child is a risk factor for CHD development. The analysis of the ordinal number of pregnancy revealed that the second and the third pregnancies are probable risk factors for the development of this pathology. It was found in our study that folic acid intake during the first trimester prevented CHD development (OR 2.33). The study revealed that among stressful risk factors are: unplanned pregnancy (OR 3.13); out-of-wedlock pregnancy and stress during pregnancy. Maternal CHD increased the CHD development in offspring approximately by two times. Some factors, such as a woman doing hard physical work during pregnancy, having sedentary work during pregnancy, the mother being a housewife or having an incomplete secondary education (OR 3.61), the mother’s secondary education, the father’s incomplete secondary education (OR 18.62), the father serving in the army (OR 2.15) or being a student at the time of woman’s pregnancy (OR 2.97) were significant for CHD development in the fetal stage. A young age of the father (up to 43 years) was also considered as one of the risk factors. This article is expected to provide timely information on risk factors for CHD development to a wide range of medical staff, including pediatric and adult cardiologists, pediatricians, thoracic surgeons, obstetricians, gynecologists, medical geneticists, genetic counselors and other relevant clinicians.

Respiratory syncytial virus seropositivity at birth is associated with adverse neonatal respiratory outcomes

BACKGROUND

More than 60 years since the discovery of the respiratory syncytial virus (RSV), the effects of prenatal exposure to this virus remain largely unknown. In this investigation, we sought to find evidence of RSV seroconversion in cord blood and explore its clinical implications for the newborn.

METHODS

Offspring from 22 pregnant women with a history of viral respiratory infection during the third trimester of pregnancy (respiratory viral illness [RVI] group) and 40 controls were enrolled in this study between 1 September 2016 and 31 March 2019. Cord blood sera were tested for anti-RSV antibodies by indirect fluorescent antibody assay. RSV seropositivity was defined as the presence of anti-RSV immunoglobulin M (IgM) or immunoglobulin A (IgA), in addition to IgG in cord blood serum at ≥1:20 dilution.

RESULTS

Anti-RSV IgG was present in all cord blood serum samples from infants born to RVI mothers (95% confidence interval [CI] = 82%-100%), with 16 samples also having elevated titers for either anti-RSV IgA or IgM (73%; 95% CI = 52%-87%). No controls had evidence of anti-RSV antibodies. Eight (50%) seropositive newborns developed at least one respiratory tract finding, including respiratory distress syndrome (N = 8), respiratory failure (N = 3), and pneumonia (N = 1). RSV seropositive newborns also required more days on oxygen, had leukocytosis and elevated C-reactive protein (P = .025, P = .047, and P < .001, respectively).

CONCLUSION

This study provides evidence of acute seropositivity against RSV in cord blood of newborns delivered from mothers with a history of upper respiratory tract illness in the third trimester. Cord blood seropositivity for anti-RSV IgA or IgM was associated with adverse clinical and laboratory outcomes in newborns.

Maternal Immunization

Vaccines administered to women during pregnancy can provide protection against serious infectious diseases for the mother, for the newborn, or both. Maternal immunization boosts the concentration of maternal antibodies that can be transferred across the placenta to directly protect infants too young to be immunized. In addition, indirect protection through prevention of maternal infection and through breast milk antibodies can be achieved through maternal immunization. In general, inactivated vaccines are considered safe for pregnant women and their fetuses, whereas live vaccines are avoided owing to the theoretical potential risk to the fetus. However, the risks and benefits of vaccination must be carefully weighed and whenever possible, protection to the mother and her infant should be prioritized. Influenza and tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccines are routinely recommended for all pregnant women in the United States. Seasonal inactivated influenza vaccine is recommended for all pregnant women in any trimester of pregnancy, mainly to protect the mother, but there is growing evidence that infants benefit from passive antibody protection against influenza complications. The Tdap vaccine is recommended during the third trimester of each pregnancy to provide optimal protection to infants who are at particularly high risk of pertussis complications and mortality in the first 3 months of life. The effects of maternal immunization on the prevention of maternal and infant disease have been demonstrated in observational and prospective studies of influenza and pertussis disease in the United States and worldwide. Maternal immunization has the potential to improve the health of mothers and young infants and therefore, other diseases of relevance during this period are now targets of active research and vaccine development, including group B streptococcus and respiratory syncytial virus. Similarly, several vaccines can be administered during pregnancy in special circumstances, when maternal health, travel, or other special situations arise. This article reviews the current recommendations for vaccination of women during pregnancy.

Respiratory syncytial virus

Respiratory Syncytial Virus (RSV) is a leading cause of hospitalization and mortality associated with lower respiratory tract illness in infants and young children worldwide. The World Health Organization recognizes the need to develop and implement prevention strategies to reduce the impact of RSV in early life as a global health priority. RSV vaccination during pregnancy is a feasible strategy to achieve this goal. Vaccines for maternal immunization against RSV are in active development and could be implemented in the near future within existing maternal-child health platforms. In addition, infant protection may be achieved through either passive antibody administration or active immunization, depending on infant health status, given that options for these complementary interventions are being developed in parallel to vaccines for maternal immunization.

The Burden of Respiratory Syncytial Virus Infection in Adults and Reproductive-Aged Women

Currently available data on respiratory syncytial virus (RSV) disease burden in adults and reproductive-aged women are limited. These data are critically needed to assist in the advancement of strategies related to maternal RSV vaccination for the passive protection of their newborn children.

Burden of Respiratory Syncytial Virus Infection in South African Human Immunodeficiency Virus (HIV)-Infected and HIV-Uninfected Pregnant and Postpartum Women: A Longitudinal Cohort Study

Background

Limited data exist on the burden of respiratory syncytial virus (RSV) illness among pregnant women, to determine their potential benefit from RSV vaccination. We evaluated the incidence of RSV illness from midpregnancy until 24 weeks postpartum in human immunodeficiency virus (HIV)–uninfected and HIV-infected women and their infants.

Methods

Mother–infant dyads were enrolled in maternal influenza vaccine efficacy trials. These included 1060 and 1056 HIV-uninfected pregnant women in 2011 and 2012, respectively, 194 HIV-infected pregnant women in 2011, and their infants. Upper respiratory tract samples obtained at illness visits were tested for RSV.

Results

The incidence (per 1000 person-months) of RSV illness (n = 43 overall) among HIV-uninfected women was lower in 2011 (1.2; 95% confidence interval [CI], .6–2.2) than in 2012 (4.0; 95% CI, 2.8–5.6). The incidence of RSV illness (n = 5) in HIV-infected women was 3.4 (95% CI, 1.4–8.1). Maternal RSV infection was associated with respiratory symptoms including cough (72.1%), rhinorrhea (39.5%), sore throat (37.2%), and headache (42%), but fever was absent. RSV infection during pregnancy was not associated with adverse pregnancy outcomes. Postpartum, RSV infection in mothers (n = 27) was associated with concurrent infection among 51.9% of their infants and, conversely, 29.8% of mothers investigated within 7 days of their infants having an RSV illness also tested positive for RSV.

Conclusions

RSV infection is associated with respiratory illness during pregnancy and postpartum. Vaccination of pregnant women against RSV could benefit the mother, albeit primarily against nonfebrile illness, and her infant.

Clinical Trial Registration

NCT01306669 and NCT01306682.

A Cross-sectional Surveillance Study of the Frequency and Etiology of Acute Respiratory Illness Among Pregnant Women

Background

Other than influenza, little is known about the consequences of viral acute respiratory illness (ARI) on pregnant women and fetuses. Our objectives were to determine the frequency of ARI due to respiratory viruses and the associated clinical outcomes during pregnancy.

Methods

Pregnant women in their second or third trimester were enrolled if they reported having symptoms of ARI or were healthy within the preceding 2 weeks. Nasopharyngeal secretions were evaluated for respiratory viruses by molecular diagnostic assays. Clinical outcomes were evaluated at enrollment and via a follow-up telephone-based questionnaire 2 weeks later.

Results

There were 155 pregnant participants, with 81 ARI cases and 91 healthy controls. Acute lower respiratory tract illness (ALRTI) was identified in 29 cases (36%). Human rhinovirus (HRV), respiratory syncytial virus (RSV), and influenza virus accounted for 75% of virus-positive cases of ALRTI. Cases with ALRTI often reported a longer duration of illness, history of allergies, symptoms of wheezing, shortness of breath, or chest pain, and use of prescription medication. Two cases with ALRTI reported decreased fetal movement; a third case with ALRTI was hospitalized.

Conclusions

In over one third of ARI cases, participants had symptoms consistent with ALRTI. Infection with HRV, RSV, or influenza virus was commonly detected in patients with ALRTI. Viral ALRTI during pregnancy appears to be common and is associated with significant morbidity.

Clinical characteristics and outcomes of respiratory syncytial virus infection in pregnant women

OBJECTIVE

To describe the clinical presentation and laboratory diagnosis of pregnant women with respiratory syncytial virus (RSV) infection.

METHODS

Pregnant women in their second and third trimester were enrolled during the course of routine prenatal care visits when they were asymptomatic within the preceding two weeks (healthy controls) or when they reported symptoms of acute respiratory illness (ARI) of ≤7 days of duration (cases). Clinical outcomes were assessed at enrollment and two weeks after. Re-enrollment was allowed. Nasal-pharyngeal secretions were evaluated for respiratory pathogens by real-time reverse transcription polymerase chain reaction (PCR). Sera were tested for RSV-specific antibody responses by Western Blot, microneutralization assay, and palivizumab competitive antibody assay.

RESULTS

During the 2015-2016 respiratory virus season, 7 of 65 (11%) pregnant women with ARI at their initial enrollment and 8 of 77 (10%) pregnant women with ARI during the study period (initial or re-enrollment) had PCR-confirmed RSV infection. Four (50%) PCR-confirmed RSV ARI cases reported symptoms of a lower respiratory tract illness (LRTI), one was hospitalized. Combining PCR and serology data, the RSV attack rate at initial enrollment was 12% (8 of 65), and 13% (10 of 77) based on ARI episodes. Among healthy controls, 28 of 88 (32%) had a Western Blot profile suggestive of a recent RSV infection either in the prior and/or current season.

CONCLUSION

RSV had an attack rate of 10-13% among ambulatory pregnant women receiving routine prenatal care during the respiratory virus season. The serology results of healthy controls suggest a potentially higher attack rate. Future studies should be aware of the combined diagnostic strength of PCR and serology to identify RSV infection. As maternal RSV vaccine candidates are evaluated to protect young infants, additional priority should be placed on outcomes of pregnant women.

Prevention of Pediatric Respiratory Syncytial Virus Lower Respiratory Tract Illness: Perspectives for the Next Decade

The landscape of infant bronchiolitis and viral pneumonia may be altered by preventive interventions against respiratory syncytial virus under evaluation today. Pediatric wards in 2018 in developing countries may differ from those attended by future generation pediatricians who may not witness the packed emergency rooms, lack of available beds, or emergency situations that all physicians caring for children with RSV experience every year. In this review, we describe and discuss different prevention strategies under evaluation to protect pediatric patients. Then, we outline a number of potential challenges, benefits, and concerns that may result from successful interventions after licensure.

A Matched Case-Control Study on the Association Between Colds, Depressive Symptoms during Pregnancy and Congenital Heart Disease in Northwestern China

The purpose of this study was to explore the association between colds, depressive symptoms during pregnancy and offspring congenital heart disease (CHD). A 1:2 matching case-control study was conducted in Northwest China. Information was gathered by a structured questionnaire and was reviewed by investigators on the spot. Multivariate logistic regressions and nonlinear mixed effect model were performed. 614 cases and 1228 controls were available in this study. After adjusting for potential confounders, the colds during the entire pregnancy were associated with increased risk of offspring CHD (OR = 1.44(1.12-1.85)). Similarly, there was a higher depression score in CHD group than the control group (OR = 1.89(1.48-2.41)). In addition, the women with both colds and higher depression scores had a higher risk of offspring CHD (OR = 2.72(1.87-3.93)) than their counterparts with only colds (OR = 1.48(1.04-2.09)) or with only higher depression scores (OR = 1.94(1.37-2.74)). The combined effects were significant in the multiplication model (OR = 2.04(1.47-2.83)) but not in the additive model (S = 1.40(0.70-2.81), AP = 0.19(-0.15-0.53) and RERI = 0.55(-0.54-1.64)). In conclusion, the colds and depressive symptoms during pregnancy were found associated with increased risk of offspring CHD and we found for the first time that there existed a statistically multiplying interaction effect of colds and depression on increasing risk of offspring CHD.

Respiratory Syncytial Virus Hospitalization During Pregnancy in 4 High-income Countries, 2010-2016

Few studies have addressed respiratory syncytial virus (RSV) infection during pregnancy. Among 846 pregnant women hospitalized with respiratory illness and tested for RSV, 21 (2%) were RSV positive, of whom 8 (38%) were diagnosed with pneumonia. Despite study limitations, these data can help inform decisions about RSV prevention strategies.

Hormonal Regulation of Physiology, Innate Immunity and Antibody Response to H1N1 Influenza Virus Infection During Pregnancy

In 2009, the H1N1 swine flu pandemic highlighted the vulnerability of pregnant women to influenza viral infection. Pregnant women infected with influenza A virus were at increased risk of hospitalization and severe acute respiratory distress syndrome (ARDS), which is associated with high mortality, while their newborns had an increased risk of pre-term birth or low birth weight. Pregnant women have a unique immunological profile modulated by the sex hormones required to maintain pregnancy, namely progesterone and estrogens. The role of these hormones in coordinating maternal immunotolerance in uterine tissue and cellular subsets has been well researched; however, these hormones have wide-ranging effects outside the uterus in modulating the immune response to disease. In this review, we compile research findings in the clinic and in animal models that elaborate on the unique features of H1N1 influenza A viral pathogenesis during pregnancy, the crosstalk between innate immune signaling and hormonal regulation during pregnancy, and the role of pregnancy hormones in modulating cellular responses to influenza A viral infection at mid-gestation. We highlight the ways in which lung architecture and function is stressed by pregnancy, increasing baseline inflammation prior to infection. We demonstrate that infection disrupts progesterone production and upregulates inflammatory mediators, such as cyclooxygenase-2 (COX-2) and prostaglandins, resulting in pre-term labor and spontaneous abortions. Lastly, we profile the ways in which pregnancy alters innate and adaptive cellular immune responses to H1N1 influenza viral infection, and the ways in which these protect fetal development at the expense of effective long-term immune memory. Thus, we highlight advancements in the field of reproductive immunology in response to viral infection and illustrate how that knowledge might be used to develop more effective post-infection therapies and vaccination strategies.

A multifaceted approach to RSV vaccination

Respiratory Syncytial Virus (RSV) is the leading cause of pneumonia and bronchiolitis in infants, resulting in significant morbidity and mortality worldwide. In addition, RSV infections occur throughout different ages, thus, maintaining the virus in circulation, and increasing health risk to more susceptible populations such as infants, the elderly, and the immunocompromised. To date, there is no vaccine approved to prevent RSV infection or minimize symptoms of infection. Current clinical trials for vaccines against RSV are being carried out in four very different populations. There are vaccines that target two different pediatric populations, infants 2 to 6 month of age and seropositive children over 6 months of age, as well as women (non-pregnant or pregnant in their third trimester). There are vaccines that target adult and elderly populations. In this review, we will present and discuss RSV vaccine candidates currently in clinical trials. We will describe the preclinical studies instrumental for their advancement, with the goal of introducing new preclinical models that may more accurately predict the outcome of clinical vaccine studies.

Efficacy of a respiratory syncytial virus vaccine candidate in a maternal immunization model

Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in infants. Maternal immunization is an option to increase maternal antibody levels and protect infants from infection. Here we assess the efficacy of virus-like particle (VLP) vaccine candidates containing stabilized pre-fusion (pre-F) or post-fusion (post-F) conformations of the RSV F protein and the attachment RSV G protein in a maternal immunization model using cotton rats. VLP vaccines containing RSV F and G proteins strongly boost pre-existing RSV immunity in dams preventing their perinatal drop in immunity. Boosting is stronger for the pre-F VLP than for the post-F VLP or purified subunit F protein vaccines, giving an advantage on mothers’ protection. VLP immunization of dams provides significant protection to pups from RSV challenge and reduced pulmonary inflammation. Collectively, our results show that a VLP vaccine with RSV F and G proteins is safe and effective for maternal and adult vaccination.

RSV infection is a major cause of bronchiolitis in infants and maternal vaccination is a potential preventive option. Here, Blanco et al. show efficacy of a Newcastle disease virus-based virus-like particle vaccine candidate in naive and pre-exposed cotton rat dams and their offspring.

Respiratory syncytial virus is an "opportunistic" killer

Respiratory syncytial virus (RSV), responsible for more than three million yearly hospitalizations and up to 118 000 deaths in children under 5 years, is the leading pulmonary cause of death for this age group that lacks a licensed vaccine. Ninety-nine percent of deaths due to the virus occur in developing countries. In-hospital RSV fatalities affect previously healthy term infants in association with bacterial sepsis, clinically significant pneumothoraxes and, to a lesser extent, comorbid conditions. Community deaths affect low-income children from socially vulnerable families and appear to be as frequent as inpatient fatalities. In industrialized countries, RSV deaths occur almost exclusively in children with premorbid conditions. In a sense, RSV is an "opportunistic" killer. It needs a synergistic premorbid, medical practice-related, infectious, or social co-factor to cause a fatal outcome. But while the complex problems associated with these co-factors await solutions, candidate vaccines, long-lived monoclonal antibodies and antivirals against RSV are under clinical evaluation. It seems reasonable to predict that the landscape of RSV infections will look different in the next decade.

Human Metapneumovirus and Other Respiratory Viral Infections during Pregnancy and Birth, Nepal

Human metapneumovirus (HMPV) is a respiratory virus that can cause severe lower respiratory tract disease and even death, primarily in young children. The incidence and characteristics of HMPV have not been well described in pregnant women. As part of a trial of maternal influenza immunization in rural southern Nepal, we conducted prospective, longitudinal, home-based active surveillance for febrile respiratory illness during pregnancy through 6 months postpartum. During 2011-2014, HMPV was detected in 55 of 3,693 women (16.4 cases/1,000 person-years). Twenty-five women were infected with HMPV during pregnancy, compared with 98 pregnant women who contracted rhinovirus and 7 who contracted respiratory syncytial virus. Women with HMPV during pregnancy had an increased risk of giving birth to infants who were small for gestational age. An intervention to reduce HMPV febrile respiratory illness in pregnant women may have the potential to decrease risk of adverse birth outcomes in developing countries.

Propensity Score-Matched Analysis on the Association Between Pregnancy Infections and Adverse Birth Outcomes in Rural Northwestern China

The purpose of this study is to examine the relationship between infections and birth outcomes in pregnant Chinese women by using propensity score (PS) matching. The data used here was from a large population-based cross-sectional epidemiological survey on birth defects in Shaanxi province, Northwest China. The babies born during 2010–2013 and their mothers were selected with a stratified multistage sampling method. We used PS-matched (1:1) analysis to match participants with infections to participants without infections. Of 22916 rural participants, the overall prevalence of infection was about 39.96%. 5381 pairs were matched. We observed increased risks of birth defects with infections, respiratory infections and genitourinary infections during the pregnancy (OR, 1.59; 95% CI: 1.21–2.08; OR, 1.44; 95% CI: 1.10–1.87; OR, 3.11; 95% CI: 1.75–5.54). There was also a significant increase of low birth weight associated with respiratory infections (1.13(1.01–1.27)). The association of birth defect with the infection could be relatively stable but the effect could be mediated by some important factors such as mother’s age, education level and economic level. The infection during pregnancy is common in Chinese women and might increase the risk of offspring birth defects and low birth weight, especially in younger, lower education, poor pregnant women.

Pregnancy and infection: using disease pathogenesis to inform vaccine strategy

Vaccination is the mainstay of preventative medicine for many infectious diseases. Pregnant women, unborn fetuses, and neonates represent three at-risk populations that can be simultaneously protected by strategic vaccination protocols. Because the pathogenesis of different infectious microbes varies based on tissue tropism, timing of infection, and host susceptibility, the goals of immunization are not uniform across all vaccines. Mechanistic understanding of infectious disease pathogenesis and immune responses is therefore essential to inform vaccine design and the implementation of appropriate immunization protocols that optimize protection of pregnant women, fetuses, and neonates.

Respiratory syncytial virus seasonality and its implications on prevention strategies

With maternal and infant vaccines against respiratory syncytial virus (RSV) in development, it is timely to consider how the deployment of these vaccines might vary according to local RSV disease seasonality. In temperate regions RSV infection is predictably limited to a period of 3 to 5 months, while in tropical regions disease seasonality is often both more variable and more prolonged. Accordingly, in tropical regions a year-round immunisation schedule for both maternal and infant immunisation might be appropriate. In contrast, in temperate regions the benefit of year-round maternal immunisation would be heavily dependent on the duration of protection this provided, potentially necessitating a strategy directed at children due to be born in the months immediately prior to the RSV season. This review will consider the impact of seasonality on maternal and infant immunisation strategies against RSV, and the potential of an alternative approach of passive immunisation for all infants immediately prior to the RSV season.

Immunization During Pregnancy: Impact on the Infant

Maternal immunization has undergone a paradigm shift in recent years, as women and healthcare providers accept and recognize the benefits of this strategy not only for the pregnant woman but also for the developing fetus and young infant. This article reviews the evidence for active immunization during pregnancy, with an emphasis on perinatal and infant outcomes. Current recommendations for immunization during pregnancy are presented, with particular focus on the routinely recommended vaccines during pregnancy: influenza and Tdap (tetanus, diphtheria, and pertussis). We discuss future research directions, maternal vaccines in development, and considerations for optimizing and advancing this underutilized strategy.

Preclinical assessment of safety of maternal vaccination against respiratory syncytial virus (RSV) in cotton rats

Maternal immunization directed to control RSV infection in newborns and infants is an appealing vaccination strategy currently under development. In this work we have modeled maternal vaccination against RSV in cotton rats (CR) to answer two fundamental questions on maternal vaccine safety. We tested (i), whether a known, unsafe RSV vaccine (i.e., FI-RSV Lot 100 vaccine) induces vaccine enhanced disease in the presence of passively transferred, RSV maternal immunity, and (ii) whether the same FI-RSV vaccine could induce vaccine enhanced disease in CR litters when used to immunize their RSV-primed mothers. Our data show that FI-RSV immunization of pups with subsequent RSV infection results in vaccine-enhanced disease independent of whether the pups were born to RSV-seropositive or RSV-seronegative mothers, and that FI-RSV immunization of RSV-seropositive mothers does not present a health risk to either the mother or the infant. Our study also raises a novel concern regarding infant immunization, namely that "safe" RSV vaccines (e.g., live RSV administered intramuscularly) may induce vaccine-enhanced disease in RSV-infected pups born to seropositive mothers. Finally, we describe for the first time a sharp decrease in RSV neutralizing antibody titers in immunized seropositive CR at the time of delivery. This decline may reflect maternal immune suppression, potentially pinpointing a window of increased vulnerability to RSV infection that could be alleviated by effective immunization of expectant mothers.

Passive and active immunization against respiratory syncytial virus for the young and old

INTRODUCTION

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in infants worldwide and also causes significant disease in the elderly. Despite 60 years of RSV research and vaccine development, there is only one approved medicine to prevent RSV infections. Palivizumab, a monoclonal antibody (mAb) against the RSV fusion (F) protein, is indicated for preterm infants and children at high-risk for RSV infections. It is an active time in RSV vaccine and mAb development with 14 vaccines and 2 mAbs currently being tested in clinical trials as of 13 February 2017. Active vaccination of women in the third trimester or passive immunization of infants with a mAb are particularly attractive approaches as the most severe disease occurs within the first 6 months of life. Areas covered: Here, we review current approaches for preventing RSV in the young and old, describe proposed clinical endpoints for studies in pediatric and adult clinical trials and highlight results from recent and ongoing clinical studies. Expert commentary: With 16 candidates in clinical development, approval of the first RSV vaccine or mAb for the prevention of RSV in all infants or the elderly is likely to occur in the next five years.

A Phase 2 randomized, observer-blind, placebo-controlled, dose-ranging trial of aluminum-adjuvanted respiratory syncytial virus F particle vaccine formulations in healthy women of childbearing age

OBJECTIVE

Respiratory syncytial virus (RSV) causes significant morbidity and mortality in infants. We are developing an RSV fusion (F) protein nanoparticle vaccine for immunization of third trimester pregnant women to passively protect infants through transfer of RSV-specific maternal antibodies. The present trial was performed to assess the immunogenicity and safety of several formulations of RSV F vaccine in 1-dose or 2-dose schedules.

METHODS

Placebo, or vaccine with 60μg or 120μg RSV F protein and 0.2, 0.4, or 0.8mg aluminum, were administered intramuscularly on Days 0 and 28 to healthy women 18-35years old. Immunogenicity was assessed from Days 0 through 91 based on anti-F IgG and palivizumab-competitive antibody (PCA) by ELISA, and RSV A and B neutralizing antibodies by microneutralization (MN) assay. Solicited adverse events were collected through Day 7 and unsolicited adverse events through Day 91.

RESULTS

All formulations were well-tolerated, with no treatment-related serious adverse events. Anti-F IgG and PCA responses were correlated and increased after both doses, while MN increased significantly only after the first dose, then plateaued. The timeliest and most robust antibody responses followed one dose of 120μg RSV F protein and 0.4mg aluminum, but persistence through 91days was modestly (∼25%) superior following two doses of 60μg RSV F protein and 0.8mg aluminum. Western blot analysis showed RSV infections in active vaccinees were reduced by 52% overall (p=0.009 overall) over the Day 0 through 90 period.

CONCLUSIONS

RSV F nanoparticle vaccine formulations were well tolerated and immunogenic. The optimal combination of convenience and rapid response for immunization in the third trimester occurred with 120μg RSV F and 0.4mg aluminum, which achieved peak immune responses in 14days and sufficient persistence through 91days to allow for passive transfer of IgG antibodies to the fetus. NCT01960686.

Febrile Rhinovirus Illness During Pregnancy Is Associated With Low Birth Weight in Nepal

Background

Adverse birth outcomes, including low birth weight (LBW), defined as <2500 grams, small-for-gestational-age (SGA), and prematurity, contribute to 60%–80% of infant mortality worldwide and may be related to infections during pregnancy. The aim of this study was to assess whether febrile human rhinovirus (HRV) illness is associated with adverse birth outcomes.

Methods

Active household-based weekly surveillance was performed for respiratory illness episodes in pregnant women as part of a community-based, prospective, randomized trial of maternal influenza immunization in rural Nepal. Rhinovirus (HRV) febrile illness episodes were defined as fever plus cough, sore throat, runny nose, and/or myalgia with HRV detected on mid-nasal swab. Multivariate regression analysis evaluated the association between febrile HRV respiratory illness and adverse birth outcomes.

Results

Overall, 96 (3%) of 3693 pregnant women had HRV-positive febrile respiratory illnesses. Infants born to pregnant women with HRV febrile illness had a 1.6-fold increased risk of being LBW compared with those with non-HRV febrile illness (28 of 96 [38%] vs 109 of 458 [24%]; relative risk [RR], 1.6; 95% confidence interval [CI], 1.1–2.3). No difference in risk of LBW was observed between infants born to mothers with non-HRV febrile respiratory illness and those without respiratory illness during pregnancy (109 of 458 [24%] vs 552 of 2220 [25%], respectively; RR, 1.0; 95% CI, 0.8–1.2).

Conclusions

Febrile illness due to rhinovirus during pregnancy was associated with increased risk of LBW in a rural South Asian population. Interventions to reduce the burden of febrile respiratory illness due to rhinovirus during pregnancy may have a significant impact on LBW and subsequent infant mortality.

Potential Cost-Effectiveness of RSV Vaccination of Infants and Pregnant Women in Turkey: An Illustration Based on Bursa Data

Background

Worldwide, respiratory syncytial virus (RSV) is considered to be the most important viral cause of respiratory morbidity and mortality among infants and young children. Although no active vaccine is available on the market yet, there are several active vaccine development programs in various stages. To assess whether one of these vaccines might be a future asset for national immunization programs, modeling the costs and benefits of various vaccination strategies is needed.

Objectives

To evaluate the potential cost-effectiveness of RSV vaccination of infants and/or pregnant women in Turkey.

Methods

A multi-cohort static Markov model with cycles of one month was used to compare the cost-effectiveness of vaccinated cohorts versus non-vaccinated cohorts. The 2014 Turkish birth cohort was divided by twelve to construct twelve monthly birth cohorts of equal size (111,459 new-borns). Model input was based on clinical data from a multicenter prospective study from Bursa, Turkey, combined with figures from the (inter)national literature and publicly available data from the Turkish Statistical Institute (TÜÏK). Incremental cost-effectiveness ratios (ICERs) were expressed in Turkish Lira (TL) per quality-adjusted life year (QALY) gained.

Results

Vaccinating infants at 2 and 4 months of age would prevent 145,802 GP visits, 8,201 hospitalizations and 48 deaths during the first year of life, corresponding to a total gain of 1650 QALYs. The discounted ICER was estimated at 51,969 TL (26,220 US $ in 2013) per QALY gained. Vaccinating both pregnant women and infants would prevent more cases, but was less attractive from a pure economic point of view with a discounted ICER of 61,653 TL (31,106 US $ in 2013) per QALY. Vaccinating only during pregnancy would result in fewer cases prevented than infant vaccination and a less favorable ICER.

Conclusion

RSV vaccination of infants and/or pregnant women has the potential to be cost-effective in Turkey. Although using relatively conservative assumptions, all evaluated strategies remained slightly below the threshold of 3 times the GDP per capita.

Clinical Presentation and Birth Outcomes Associated with Respiratory Syncytial Virus Infection in Pregnancy

Background

Respiratory syncytial virus (RSV) is the most important cause of viral pneumonia in children worldwide. A maternal vaccine may protect both the mother and infant from RSV illness. The epidemiology and clinical presentation of RSV in pregnant and postpartum women is not well-described.

Methods

Data were collected from a prospective, randomized trial of influenza immunization in pregnant women in rural southern Nepal. Women were enrolled in their second trimester of pregnancy and followed until six months postpartum. Active weekly home-based surveillance for febrile respiratory illness was performed. Mid-nasal swabs collected with episodes of respiratory illness were tested for RSV by real-time polymerase chain reaction.

Results

RSV was detected in 14 (0.4%) illness episodes in 3693 women over 3554 person-years of surveillance from 2011–2014. RSV incidence was 3.9/1000 person-years overall, and 11.8/1000 person-years between September and December. Seven (50%) women sought care for RSV illness; none died. Of the 7 (50%) illness episodes during pregnancy, all had live births with 2 (29%) preterm births and a median birthweight of 3060 grams. This compares to 469 (13%) preterm births and a median birthweight of 2790 grams in women without RSV during pregnancy. Of the 7 mothers with postpartum RSV infection, RSV was detected in 4 (57%) of their infants.

Conclusions

RSV was an uncommon cause of febrile respiratory illness in mothers during pregnancy in Nepal. These data will inform prevention and therapeutic strategies against RSV in resource-limited settings.