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

A Retrospective Cross-Sectional Analysis of Viral SARI in Pregnant Women in Southern Brazil

Pregnant women (PW) are at a higher risk of diseases and hospitalization from viral respiratory infections, particularly influenza and SARS-CoV-2, due to cardiopulmonary and immunological changes. This study assessed the impact of viral respiratory infections on PW hospitalized with severe acute respiratory infection (SARI) prior to the COVID-19 pandemic. It is a cross-sectional study with 42 PW and 85 non-pregnant women (NPW) admitted with SARI to two tertiary hospitals between January 2015 and December 2019. The rates of virus prevalence, SARI hospitalization, length of hospital stay, oxygen supplementation, intensive care unit (ICU) admission, and death were comparable between PW and NPW. A multivariate analysis showed that PW had a higher rate of viral SARI hospitalizations (OR = 2.37; 95% CI = 1.02-5.48) as compared to NPW, with the influenza virus being the most prevalent (aOR = 7.58; 95% CI = 1.53-37.66). The length of hospital stays (aOR = 0.83; 95% CI = 0.73-0.95) and admissions to the ICU (aOR = 0.028; 95% CI = 0.004-0.25) were lower in PW as compared to hospitalized NPW. The influenza virus had a greater impact on the frequency of SARI in the group of PW, and these had a better outcome than NPW due to the earlier antiviral treatment they received.

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.

What U.S. Obstetricians Need to Know About Respiratory Syncytial Virus

Respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory tract infections in neonates, infants, and children worldwide. The virus is estimated to infect 97% of this population in the United States by the age of 2 years, leading to hospitalization for severe lower respiratory tract disease in 2-3% of infants younger than age 6 months. Two preventive options, prenatal administration of a maternal vaccine and administration of a long-acting monoclonal antibody to the infant, are now available for the prevention of RSV-associated lower respiratory tract infection in infants in the United States. The U.S. Food and Drug Administration (FDA) has approved and the Centers for Disease Control and Prevention (CDC) has recommended a new maternal vaccination, RSVPreF, to be administered between 32 0/7 and 36 6/7 weeks of gestation to reduce the risk of RSV-associated lower respiratory tract infection in infants in the first 6 months of life. The monoclonal antibody nirsevimab was approved by the FDA and recommended by the CDC for prevention of RSV-associated lower respiratory tract infection in infants younger than age 8 months who are born during or entering their first RSV season and for infants and children aged 8-19 months who are at high risk for RSV-associated lower respiratory tract infection and entering their second RSV season. Either maternal vaccination during pregnancy or monoclonal antibody administration to the infant is recommended to prevent RSV-associated lower respiratory tract infection among infants, but both are not needed for most infants. Given that the availability of these products may vary as these recommendations are implemented, it is important that obstetricians and other prenatal practitioners have the information they need to counsel their pregnant patients about both options. We review the safety and efficacy of these products, current recommendations for their use, and relative advantages and disadvantages of both newly approved options for the prevention of RSV-associated lower respiratory tract infection in infants to assist obstetricians and other prenatal practitioners in their counseling of pregnant patients.

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.

Incidence of Respiratory Syncytial Virus Infection in Older Adults: Limitations of Current Data

INTRODUCTION

Respiratory syncytial virus (RSV) is an important cause of severe respiratory illness in older adults and adults with respiratory or cardiovascular comorbidities. Published estimates of its incidence and prevalence in adult groups vary widely. This article reviews the potential limitations affecting RSV epidemiology studies and suggests points to consider when evaluating or designing them.

METHODS

Studies reporting the incidence or prevalence of RSV infection in adults in high-income Western countries from 2000 onwards were identified via a rapid literature review. Author-reported limitations were recorded, together with presence of other potential limitations. Data were synthesized narratively, with a focus on factors affecting incidence estimates for symptomatic infection in older adults.

RESULTS

A total of 71 studies met the inclusion criteria, most in populations with medically attended acute respiratory illness (ARI). Only a minority used case definitions and sampling periods tailored specifically to RSV; many used influenza-based or other criteria that are likely to result in RSV cases being missed. The great majority relied solely on polymerase chain reaction (PCR) testing of upper respiratory tract samples, which is likely to miss RSV cases compared with dual site sampling and/or addition of serology. Other common limitations were studying a single season, which has potential for bias due to seasonal variability; failure to stratify results by age, which underestimates the burden of severe disease in older adults; limited generalizability beyond a limited study setting; and absence of measures of uncertainty in the reporting of results.

CONCLUSIONS

A significant proportion of studies are likely to underestimate the incidence of RSV infection in older adults, although the effect size is unclear and there is also potential for overestimation. Well-designed studies, together with increased testing for RSV in patients with ARI in clinical practice, are required to accurately capture both the burden of RSV and the potential public health impact of vaccines.

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.

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.

Effects of Vertical Transmission of Respiratory Viruses to the Offspring

Overt and subclinical maternal infections in pregnancy can have multiple and significant pathological consequences for the developing fetus, leading to acute perinatal complications and/or chronic disease throughout postnatal life. In this context, the current concept of pregnancy as a state of systemic immunosuppression seems oversimplified and outdated. Undoubtedly, in pregnancy the maternal immune system undergoes complex changes to establish and maintain tolerance to the fetus while still protecting from pathogens. In addition to downregulated maternal immunity, hormonal changes, and mechanical adaptation (e.g., restricted lung expansion) make the pregnant woman more susceptible to respiratory pathogens, such as influenza virus, respiratory syncytial virus (RSV), and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Depending on the infectious agent and timing of the infection during gestation, fetal pathology can range from mild to severe, and even fatal. Influenza is associated with a higher risk of morbidity and mortality in pregnant women than in the general population, and, especially during the third trimester of pregnancy, mothers are at increased risk of hospitalization for acute cardiopulmonary illness, while their babies show higher risk of complications such as prematurity, respiratory and neurological illness, congenital anomalies, and admission to neonatal intensive care. RSV exposure in utero is associated with selective immune deficit, remodeling of cholinergic innervation in the developing respiratory tract, and abnormal airway smooth muscle contractility, which may predispose to postnatal airway inflammation and hyperreactivity, as well as development of chronic airway dysfunction in childhood. Although there is still limited evidence supporting the occurrence of vertical transmission of SARS-CoV-2, the high prevalence of prematurity among pregnant women infected by SARS-CoV-2 suggests this virus may alter immune responses at the maternal-fetal interface, affecting both the mother and her fetus. This review aims at summarizing the current evidence about the short- and long-term consequences of intrauterine exposure to influenza, RSV, and SARS-CoV-2 in terms of neonatal and pediatric outcomes.

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.

Transplacental Antibody Transfer of Respiratory Syncytial Virus Specific IgG in Non-Human Primate Mother-Infant Pairs

One approach to protect new-borns against respiratory syncytial virus (RSV) is to vaccinate pregnant women in the last trimester of pregnancy. The boosting of circulating antibodies which can be transferred to the foetus would offer immune protection against the virus and ultimately the disease. Since non-human primates (NHPs) have similar reproductive anatomy, physiology, and antibody architecture and kinetics to humans, we utilized this preclinical species to evaluate maternal immunization (MI) using an RSV F subunit vaccine. Three species of NHPs known for their ability to be infected with human RSV in experimental challenge studies were tested for RSV-specific antibodies. African green monkeys had the highest overall antibody levels of the old-world monkeys evaluated and they gave birth to offspring with anti-RSV titers that were proportional to their mother. These higher overall antibody levels are associated with greater durability found in their offspring. Immunization of RSV seropositive AGMs during late pregnancy boosts RSV titers, which consequentially results in significantly higher titers in the vaccinated new-borns compared to the new-borns of unvaccinated mothers. These findings, accomplished in small treatment group sizes, demonstrate a model that provides an efficient, resource sparing and translatable preclinical in vivo system for evaluating vaccine candidates for maternal immunization.

Future vaccines in pregnancy

Vaccination in pregnancy provides an important opportunity to target illnesses that are known to impact pregnant women, fetal development, and newborns in particular. The ability to create antibodies through safe vaccination that cross the placenta can provide protection against maternal, congenital, and newborn infections. At present, multiple vaccines are being developed which have direct benefits for pregnant women and their newborns. Group B streptococcus, Respiratory Syncytial Virus, Cytomegalovirus, Zika, Ebola, Malaria, and Coronavirus SARS-CoV-2 are all being researched with the view to develop a safe vaccine available for pregnant women. There is also an increased movement towards the inclusion of pregnant women in vaccine development and trials - challenging the historical, ethical, and medicolegal arguments against their involvement in such research.

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.

Mitoxantrone Shows In Vitro, but Not In Vivo Antiviral Activity against Human Respiratory Syncytial Virus

Human respiratory syncytial virus (HRSV) is the most common cause of severe respiratory infections in infants and young children, often leading to hospitalization. In addition, this virus poses a serious health risk in immunocompromised individuals and the elderly. HRSV is also a major nosocomial hazard in healthcare service units for patients of all ages. Therefore, the development of antiviral treatments against HRSV is a global health priority. In this study, mitoxantrone, a synthetic anthraquinone with previously reported in vitro antiprotozoal and antiviral activities, inhibits HRSV replication in vitro, but not in vivo in a mice model. These results have implications for preclinical studies of some drug candidates.

RSV Specific Antibodies in Pregnant Women and Subsequent Risk of RSV Hospitalization in Young Infants

Background

The fusion (F) glycoprotein of respiratory syncytial virus (RSV) represents the major neutralizing antigen, and antibodies against the pre-F conformation have the most potent neutralizing activity. This study aimed to assess the correlation between maternal antibody titers against the pre-F, post-F, and G glycoproteins and the child’s risk of developing severe RSV bronchiolitis early in infancy.

Methods

We identified previously healthy term infants <3 months of age hospitalized with RSV bronchiolitis from December 2015 to March 2016. We measured IgG antibody titers to pre-F, post-F, and G proteins in maternal sera obtained at 9–12 weeks of pregnancy of these hospitalized infants’ mothers (n = 94) and compared them with serum antibody titers of control pregnant mothers (n = 130) whose children were not hospitalized.

Results

All maternal samples (n = 224) had detectable pre-F antibodies. Pre-F antibody titers were significantly lower in mothers whose infants were hospitalized with RSV bronchiolitis compared with those mothers whose infants were not hospitalized (23.9 [range (or antibody titer range), 1.4–273.7] µg/L vs 30.6 [XXX, 3.4–220.0] µg/L; P = .0026). There were no significant differences in maternal post-F and G antibody titers between hospitalized and nonhospitalized infants.

Conclusions

Our findings indicate that maternal pre-F antibodies are fundamental for providing immune protection to the infant.

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.

The journey to a respiratory syncytial virus vaccine

OBJECTIVE

The high burden associated with respiratory syncytial virus (RSV) has made the development of RSV vaccine(s) a global health high priority. This review summarizes the journey to an RSV vaccine, the different strategies and challenges associated with the development of preventive strategies for RSV, and the diverse products that are undergoing clinical testing.

DATA SOURCES

Studies on RSV biology, immunology, epidemiology, and monoclonal antibodies (mAbs) and vaccines were searched using MEDLINE. We also searched PATH.org and ClinicalTrials.gov for updated information regarding the status of RSV vaccines and mAbs undergoing clinical trials.

STUDY SELECTIONS

We selected relevant studies conducted in infants and young children, pregnant women, and elderly population for the prevention of RSV infection.

RESULTS

Identification of a safe and immunogenic vaccine has been an important but elusive initiative for more than 60 years for different reasons, including the legacy of formalin-inactivated vaccine, our limited understanding of the immune response to RSV and how it relates to clinical disease severity, or the need for different end points according to the different vaccine platforms. Nevertheless, there are currently 39 vaccines and mAbs under development and 19 undergoing clinical trials.

CONCLUSION

Over the past decade, there have been significant advances in our knowledge of RSV molecular and structural biology and in understanding the human immune response to RSV. Despite the barriers, there are several promising mAbs and RSV vaccines undergoing clinical trials that hope to offer protection to the most vulnerable populations.

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.