Incidence, risk factors and impact of seasonal influenza in pregnancy: A national cohort study

Risk of severe influenza infection in women with a history of pregnancy complications: A longitudinal cohort study

BACKGROUND

Risk factors for influenza complications in women are poorly understood. We examined the association between pregnancy outcomes and risk of influenza hospitalization up to three decades later.

METHODS

We analyzed a cohort of 1,421,531 pregnant women who delivered in Quebec, Canada between 1989 and 2021. Patients were followed over time beginning at the first delivery. The main exposure measures included obstetric complications such as preeclampsia, gestational diabetes, and preterm birth. The main outcome was influenza hospitalization up to 32 years later. We used adjusted Cox regression models to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association between obstetric complications and risk of influenza hospitalization following pregnancy.

RESULTS

A total of 4,016 women were hospitalized for influenza during 32 years of follow-up. Influenza hospitalization was more frequent among women with pregnancy complications than women without complications (18.0 vs 14.1 per 100,000 person-years). Compared with no pregnancy complication, women with gestational diabetes (HR 1.48, 95% CI 1.30-1.69), preeclampsia (HR 1.45, 95% CI 1.28-1.65), placental abruption (HR 1.36, 95% CI 1.12-1.66), preterm birth (HR 1.40, 95% CI 1.27-1.55), cesarean section (HR 1.22, 95% CI 1.13-1.31), and severe maternal morbidity (HR 1.43, 95% CI 1.22-1.68) had a greater risk of influenza hospitalization later in life. These pregnancy outcomes were associated with severe influenza infections requiring critical care.

CONCLUSIONS

Women with pregnancy complications have an elevated risk of severe influenza complications later in life and have potential to benefit from seasonal vaccination to prevent influenza hospitalization.

The 2020 immunization programme landscape: Piloting an assessment metric to evaluate the maturity of national immunization programmes across the life course

BACKGROUND

The World Health Organization (WHO) encourages countries to provide appropriate vaccinations for children, adolescents, and relevant adult populations. Childhood programme have been the focus of global investments, but recent pandemics have increasingly demonstrated the value of life course vaccination. Our objective is to compare national life course immunization programmatic maturity prior to mass COVID-19 vaccine introduction, the largest adult vaccination programme, globally. As coverage estimates (typically used to assess childhood programmes) are not available for adult vaccinations, this analysis pilots a standardized quantitative metric of programmatic maturity.

METHODS

Through consultation with vaccination experts, we developed a standardized approach to assess national immunization programme maturity across the life course. In accordance with expert input, five vaccines were selected to represent delivery across the life course: diphtheria tetanus toxoid and pertussis (DTP); measles (MCV) second dose; human papillomavirus (HPV) final dose; pneumococcal conjugate (PCV) final dose; and seasonal influenza annual dose. Experts recommended inclusion of the following indicators for each vaccine: a legal mandate (national policy), experience delivering the vaccine (programme duration), and vaccine use (uptake for relevant populations). We developed a metric accordingly that provides up to 5 points per vaccine ("vaccine specific maturity score") which when summed forms the "life course maturity score", with a maximum score of 25. We analysed the prevalence of national policies, experience, and use by region and World Bank income group.

RESULTS

More than 55% of the 194 WHO Member States had childhood vaccine policies for all three of the vaccines considered (DTP, MCV, and PCV) compared to 60% for HPV (proxy for adolescent vaccination programme) and 52% for seasonal influenza (proxy for adult vaccination programme). Childhood vaccination programmes (e.g., MCV and DTP) had the highest vaccine specific maturity scores, while seasonal influenza and HPV vaccination programmes had much lower scores. The national life course maturity scores ranged from 1 to 23, with a global median of 12 (IQR: 8; 16).

DISCUSSION

The piloted metric provides an overview of the maturity of life course immunization programmes. The metric is structured to be a flexible, rapid resource that can be used to assess other combinations of vaccines across the life course. The findings from this paper provide a baseline of immunization programme maturity for childhood, adolescent, and adult vaccination programmes immediately prior to the COVID-19 vaccine introduction. This maturity score, or adaptations of this approach, could be used to monitor the trajectory of national immunization programme maturity across the life course in the years ahead.

Birth Outcomes After Pertussis and Influenza Diagnosed in Pregnancy: A Retrospective, Population-Based Study

OBJECTIVE

Adverse birth outcomes and the maternal severity of influenza in pregnancy are well documented but information on pertussis is limited.

DESIGN

Population-based linkage data were collected during 2001-2016.

SETTING

New South Wales, Australia.

POPULATION OR SAMPLE

A total of 1 453 037 singleton births.

METHODS

Cox regression was used to estimate the associations between pertussis or influenza during pregnancy and birth outcomes with adjustment of covariates.

MAIN OUTCOME MEASURES

Adverse birth outcomes (preterm birth and low birth weight).

RESULTS

Among 1 453 037 singleton births over 16 years, we identified pertussis in 925 (49; 5.3% hospitalised) and influenza in 2850 (1092; 38.3% hospitalised) women during pregnancy. Cases of pertussis were similarly distributed by trimester (32% 3rd) whereas 46% of influenza cases were in the 3rd trimester. Younger age, previous birth, and being overseas-born were associated with both pertussis and influenza, whereas identifying as Aboriginal or Torres Strait Islander, hypertension or diabetes before and during pregnancy, and a number of other factors were only associated with influenza. Both pertussis and influenza in pregnancy were associated with increased risk of preterm birth (pertussis: aHR = 1.30, 95% CI 1.01-1.68; influenza: aHR = 1.56, 95% CI 1.36-1.79) and these increased risks were greater when infections in the period within 2 weeks of birth were considered (pertussis: aHR = 2.36, 95% CI 1.26-4.41; influenza: aHR = 2.29, 95% CI 1.78-2.96).

CONCLUSIONS

Maternal pertussis and influenza infections close to the time of birth were associated with adverse birth outcomes. These findings highlight the benefits of vaccination during pregnancy.

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.

Summary of the National Advisory Committee on Immunization (NACI) Updated Guidance on Influenza Vaccination During Pregnancy

Background

Seasonal influenza infection can lead to serious complications and adverse outcomes for pregnant individuals, the developing fetus and infants younger than six months of age. This supplemental statement provides an evidence summary on the safety and effectiveness of influenza vaccination in pregnant individuals, and the benefits and risks to the pregnant person, the developing fetus and infants younger than six months of age.

Methods

A systematic review was conducted on the effectiveness and safety of influenza vaccination in pregnancy. The National Advisory Committee on Immunization (NACI)'s evidence-based process was used to assess the quality of eligible studies, summarize and analyze the findings, and apply an ethics, equity, feasibility and acceptability lens to develop recommendations.

Results

The evidence suggests that influenza vaccination during pregnancy is effective in reducing the risk of laboratory-confirmed influenza infection and hospitalization in both pregnant individuals and their infants up to six months postpartum. The evidence also suggests that influenza vaccination during pregnancy does not increase the risk of non-obstetric serious adverse events in pregnant persons, infant death, spontaneous abortion, stillbirth, preterm birth, small for gestational age, low birth weight and congenital anomalies.

Conclusion

Based on this body of evidence, NACI reaffirms the safety and importance of influenza vaccination during pregnancy. NACI recommends that individuals at any stage of pregnancy should receive an age-appropriate inactivated, unadjuvanted or recombinant influenza vaccine each influenza season. Influenza vaccination may be given at the same time as, or at any time before or after administration of another vaccine, including the coronavirus disease 2019 (COVID-19) or pertussis vaccines.

Suppression of progesterone by influenza A virus mediates adverse maternal and fetal outcomes in mice

Influenza A virus infection during pregnancy can cause adverse maternal and fetal outcomes but the mechanism responsible remains elusive. Infection of outbred mice with 2009 H1N1 at embryonic day (E) 10 resulted in significant maternal morbidity, placental tissue damage and inflammation, fetal growth restriction, and developmental delays that lasted through weaning. Restriction of pulmonary virus replication was not inhibited during pregnancy, but infected dams had suppressed circulating and placental progesterone (P4) concentrations that were caused by H1N1-induced upregulation of pulmonary cyclooxygenase (COX)-1-, but not COX-2-, dependent synthesis and secretion of prostaglandin (PG) F2α. Treatment with 17-α-hydroxyprogesterone caproate (17-OHPC), a synthetic progestin that is safe to use in pregnancy, ameliorated the adverse maternal and fetal outcomes from H1N1 infection and prevented placental cell death and inflammation. These findings highlight the therapeutic potential of progestin treatments for influenza during pregnancy.IMPORTANCEPregnant individuals are at risk of severe outcomes from both seasonal and pandemic influenza A viruses. Influenza infection during pregnancy is associated with adverse fetal outcomes at birth and adverse consequences for offspring into adulthood. When outbred dams, with semi-allogenic fetuses, were infected with 2009 H1N1, in addition to pulmonary virus replication, lung damage, and inflammation, the placenta showed evidence of transient cell death and inflammation that was mediated by increased activity along the arachidonic acid pathway leading to suppression of circulating progesterone. Placental damage and suppressed progesterone were associated with detrimental effects on perinatal growth and developmental delays in offspring. Treatment of H1N1-infected pregnant mice with 17-OHPC, a synthetic progestin treatment that is safe to use in pregnancy, prevented placental damage and inflammation and adverse fetal outcomes. This novel therapeutic option for the treatment of influenza during pregnancy should be explored clinically.

A scoping review of the reasons for and approaches to non-uptake of pertussis and influenza vaccinations in pregnant women in the United Kingdom and Ireland

BACKGROUND

Pertussis and influenza cause significant morbidity and mortality in pregnancy and the neonatal period. Maternal vaccination in pregnancy would reduce harm, but low vaccine uptake is a concern. This scoping review aimed to understand the reasons for, and approaches, to non-uptake of pertussis and influenza vaccinations in pregnant women in the UK and Ireland.

METHODS

The inclusion criteria of this scoping review consist of pregnant women who avail of pertussis and influenza vaccines in the UK and Ireland. MEDLINE, EMBASE, Web of Science and CINAHL databases were searched in June 2021 and updated in October 2022. Searches were limited to English language reports published after 2011. We followed the Joanna Briggs Institute guidance on scoping reviews. Data were extracted and charted.

RESULTS

Five themes emerged from the literature. Acceptability, as well as organisational and awareness issues, were overarching themes regarding reasons for and approaches to non-uptake of the vaccines respectively. Other themes included healthcare professional factors, information interpretation and pregnancy-related factors.

CONCLUSIONS

Women need clear, comprehensible information, ideally provided by their healthcare professionals, in a way that is meaningful and addresses their circumstances and risk perceptions. This research will serve as a base for future work that aims behaviour science interventions at the wider pregnant population as well as the target groups that have been identified in this review.

Evaluation of intentions to get vaccinated against influenza, COVID 19, pertussis and to get a future vaccine against respiratory syncytial virus in pregnant women

INTRODUCTION

Pregnant women (PW) are at increased risk of complications due to seasonal influenza and Covid-19. Immunization during pregnancy against pertussis and respiratory syncytial virus (RSV) protects newborns from severe diseases. Our aim was to assess intentions to get vaccinated against seasonal influenza, COVID-19, pertussis and RSV in PW and to identify factors associated with intentions.

METHODS

Cross-sectional survey in PW followed at a University Hospital in France assessing their knowledge, and attitudes toward vaccination against influenza, Covid-19, and RSV during pregnancy. Primary outcome was intention to receive each vaccine or potential vaccine. Univariable and multivariable analysis were carried out to identify factors associated with intentions to get vaccinated for each vaccine.

RESULTS

Among the 1199 PW followed during the study period, 310 completed the questionnaire. Intentions to get vaccinated were respectively 43.9 %, 36.8 %, 36.1 % and 39.4 % against influenza, Covid-19, pertussis and RSV. Overall confidence in vaccines using 5C-model, recommendation by a healthcare professional (HCP), good knowledge about diseases and vaccines and previous influenza vaccination were associated with flu vaccine acceptance with respective adjusted odds ratios and 95 % Confidence Intervals (aOR) 1.69 (1.09-2.61) by one-point increase in confidence score, 4.89 (2.24-10.7), 1.56 by one-point increase in knowledge score (1.26-1.93), 13.5 and (5.3-34.3). Confidence was also associated with Covid-19 and RSV vaccine acceptance with respective aOR and 95 % CI 2.63 (1.7-4.07) and 1.92 (1.3-2.84). For pertussis, previous flu vaccination or pertussis vaccination in the last 5 years were predictors of pertussis vaccine acceptance during the pregnancy with respective aOR and 95 % CI 1.97 (1.1-3.84) and 2.9 (1.6-5.18).

CONCLUSION

Confidence is associated with seasonal influenza, COVID-19 and RSV vaccines acceptance in pregnant women. Receiving a recommendation from a HCP was strongly associated with acceptance of influenza vaccine. Recent vaccination against pertussis was not a barrier to pertussis vaccine acceptance during pregnancy.

Suppression of progesterone by influenza A virus mediates adverse maternal and fetal outcomes in mice

Influenza A virus infection during pregnancy can cause adverse maternal and fetal outcomes, but the mechanism responsible remains elusive. Infection of outbred mice with 2009 H1N1 at embryonic day (E) 10 resulted in significant maternal morbidity, placental tissue damage and inflammation, fetal growth restriction, and developmental delays that lasted through weaning. Restriction of pulmonary virus replication was not inhibited during pregnancy, but infected dams had suppressed circulating and placental progesterone (P4) concentrations that were caused by H1N1-induced upregulation of pulmonary cyclooxygenase (COX)-1, but not COX-2-, dependent synthesis and secretion of prostaglandin (PG) F2α. Treatment with 17-α-hydroxyprogesterone caproate (17-OHPC), a synthetic progestin that is safe to use in pregnancy, ameliorated the adverse maternal and fetal outcomes from H1N1 infection and prevented placental cell death and inflammation. These findings highlight the therapeutic potential of progestin treatments for influenza during pregnancy.

ECTRIMS/EAN consensus on vaccination in people with multiple sclerosis: Improving immunization strategies in the era of highly active immunotherapeutic drugs

BACKGROUND

With the new highly active drugs available for people with multiple sclerosis (pwMS), vaccination becomes an essential part of the risk management strategy.

OBJECTIVE

To develop a European evidence-based consensus for the vaccination strategy of pwMS who are candidates for disease-modifying therapies (DMTs).

METHODS

This work was conducted by a multidisciplinary working group using formal consensus methodology. Clinical questions (defined as population, interventions, and outcomes) considered all authorized DMTs and vaccines. A systematic literature search was conducted and quality of evidence was defined according to the Oxford Centre for Evidence-Based Medicine Levels of Evidence. The recommendations were formulated based on the quality of evidence and the risk-benefit balance.

RESULTS

Seven questions, encompassing vaccine safety, vaccine effectiveness, global vaccination strategy and vaccination in sub-populations (pediatric, pregnant women, elderly and international travelers) were considered. A narrative description of the evidence considering published studies, guidelines, and position statements is presented. A total of 53 recommendations were agreed by the working group after three rounds of consensus.

CONCLUSION

This first European consensus on vaccination in pwMS proposes the best vaccination strategy according to current evidence and expert knowledge, with the goal of homogenizing the immunization practices in pwMS.

Characteristics associated with influenza vaccination uptake in pregnancy: a retrospective cohort study

BACKGROUND

Pregnant women are at increased risk from influenza, yet maternal influenza vaccination levels remain suboptimal.

AIM

To estimate associations between sociodemographic and health characteristics and seasonal influenza vaccination uptake among pregnant women, and to understand trends over time to inform interventions to improve vaccine coverage.

DESIGN AND SETTING

Retrospective cohort study using linked electronic health records of women in North West London with a pregnancy overlapping an influenza season between September 2010 and February 2020.

METHOD

A multivariable mixed-effects logistic regression model was used to identify associations between characteristics of interest and the primary outcome of influenza vaccination.

RESULTS

In total, 451 954 pregnancies, among 260 744 women, were included. In 85 376 (18.9%) pregnancies women were vaccinated against seasonal influenza. Uptake increased from 8.4% in 2010/11 to 26.4% in 2017/18, dropping again to 21.1% in 2019/20. Uptake was lowest among women aged 15-19 years (11.9%; reference category) or ≥40 years (15.2%; odds ratio [OR] 1.17, 95% confidence interval [CI] = 1.10 to 1.24); of Black (14.1%; OR 0.55, 95% CI = 0.53 to 0.57) or unknown ethnicity (9.9%; OR 0.42, 95% CI = 0.39 to 0.46); who lived in more deprived areas (OR least versus most deprived [reference category] 1.16, 95% CI = 1.11 to 1.21); or with no known risk factors for severe influenza.

CONCLUSION

Seasonal influenza vaccine uptake in pregnant women increased in the decade before the COVID-19 pandemic, but remained suboptimal. Targeted approaches are recommended to reducing inequalities in access to vaccination and should focus on women of Black ethnicity, younger and older women, and women living in deprived areas.

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.

Functional consequences of SARS-CoV-2 infection in pregnant women, fetoplacental unit, and neonate

The SARS-CoV-2 infection causes COVID-19 disease, characterized by acute respiratory distress syndrome, bilateral pneumonia, and organ failure. The consequences of maternal SARS-CoV-2 infection for the pregnant woman, fetus, and neonate are controversial. Thus, it is required to determine whether there is viral and non-viral vertical transmission in COVID-19. The disease caused by SARS-CoV-2 leads to functional alterations in asymptomatic and symptomatic pregnant women, the fetoplacental unit and the neonate. Several diseases of pregnancy, including COVID-19, affect the fetoplacental function, which causes in utero programming for young and adult diseases. A generalized inflammatory state and a higher risk of infection are seen in pregnant women with COVID-19. Obesity, diabetes mellitus, and hypertension may increase the vulnerability of pregnant women to infection by SARS-CoV-2. Alpha, Delta, and Omicron variants of SARS-CoV-2 show specific mutations that seem to increase the capacity of the virus to infect the pregnant woman, likely due to increasing its interaction via the virus S protein and angiotensin-converting enzyme 2 receptors. This review shows the literature addressing to what extent COVID-19 in pregnancy affects the pregnant woman, fetoplacental unit, and neonate. Prospective studies that are key in managing SARS-CoV-2 infection in pregnancy are discussed.

Influenza Virus Infection during Pregnancy as a Trigger of Acute and Chronic Complications

Influenza A virus (IAV) infection during pregnancy disrupts maternal and fetal health through biological mechanisms, which are to date poorly characterised. During pregnancy, the viral clearance mechanisms from the lung are sub-optimal and involve hyperactive innate and adaptive immune responses that generate wide-spread inflammation. Pregnancy-related adaptations of the immune and the cardiovascular systems appear to result in delayed recovery post-viral infection, which in turn promotes a prolonged inflammatory phenotype, increasing disease severity, and causing maternal and fetal health problems. This has immediate and long-term consequences for the mother and fetus, with complications including acute cardiopulmonary distress syndrome in the mother that lead to perinatal complications such as intrauterine growth restriction (IUGR), and birth defects; cleft lip, cleft palate, neural tube defects and congenital heart defects. In addition, an increased risk of long-term neurological disorders including schizophrenia in the offspring is reported. In this review we discuss the pathophysiology of IAV infection during pregnancy and its striking similarity to other well-established complications of pregnancy such as preeclampsia. We discuss general features of vascular disease with a focus on vascular inflammation and define the "Vascular Storm" that is triggered by influenza infection during pregnancy, as a pivotal disease mechanism for short and long term cardiovascular complications.

Epidemiological characteristics and risk factors of obstetric infection after the Universal Two-Child Policy in North China: a 5-year retrospective study based on 268,311 cases

BACKGROUND

Obstetrical infection is one of the causes of maternal death and a difficult problem for many clinicians. Changes in the demographic and obstetric background of pregnant women following the Universal Two-Child Policy may have an impact on some fertility phenomena. And with the increase in the number of deliveries, the limited medical resources become more scarce. How will China's health system quickly adapt to the growing needs and expectations for maternal health and ensure the provision of qualified and accessible medical services? In addition, what social support measures should be provided to reduce preventable obstetric complications? Given the relatively low per capita share of medical resources in China, how should China deal with the impact of the Universal Two-Child Policy? Therefore, more studies based on the change of fertility policy are needed. We try to analyze the epidemiological characteristics and risk factors of obstetric infection before and after the Universal Two-Child Policy, with a view to providing reference for the prevention and control of obstetric infection in regions after the change of fertility policy, and also hope to make corresponding contributions to the solution of the above problems through relevant studies.

METHODS

The subjects of the survey were 268,311 pregnant women from Hebei Province Maternal Near Miss Surveillance System (HBMNMSS) of Hebei Women and Children's Health Center from January 1, 2013 to December 31, 2017. We analyzed the region, time and population distribution characteristics of obstetric infection, compared the epidemiological factors of obstetric infection before and after the Universal Two-Child Policy, and analyzed the relevant risk factors of obstetric infection.

RESULTS

The incidence of obstetric infection increased nearly twice after the Universal Two-Child Policy. The incidence of obstetric infection was highest in Chengde (1.9%), a city with a northward geographical distribution, Baoding (1.6%), Cangzhou (1.5%) followed; The higher the hospital grade, the higher the incidence; The incidence of obstetric infections in hospitals at all levels has increased; The age of onset before the Universal Two-Child Policy was (27.82 ± 5.047) years old, and the age after the Universal Two-Child Policy was (28.97 ± 4.880) years old; The incidence of obstetric infections is higher in winter. The rate of abortion-related infection (increased from 0.61 to 1.65%) and the rate of pregnant women with high school education (increased from 0.35 to 0.74%) increased significantly. The results of multivariate Logistic regression analysis after the Universal Two-Child Policy showed that anemia (OR = 1.249, 95%CI: 1.071-1.458), chronic hypertension (OR = 1.934, 95%CI: 1.375-2.722), mild preeclampsia (OR = 2.103, 95%CI: 1.323-3.344) and severe preeclampsia (OR = 2.228, 95%CI: 1.703-2.916) were independent risk factors for obstetric infection. Gestational age ≥ 37 weeks was a protective factor.

CONCLUSION

After the Universal Two-Child Policy, the prevention and control of obstetric infections should be strengthened, especially for abortion-related infections and elderly maternal with obstetric complications and complication in high-grade hospitals in winter. Educational background is also one of the factors that should be considered in the prevention of obstetric sensation. Prolonging gestational age is helpful to reduce the incidence of obstetric infection.

Upregulated influenza A viral entry factors and enhanced interferon-alpha response in the nasal epithelium of pregnant rats

Despite the increased severity of influenza A infection in pregnancy, knowledge about the expression of cell entry factors for influenza A virus (IAV) and the innate immune response in the nasal epithelium, the primary portal of viral entry, is limited. Here, we compared the expression of IAV cell entry factors and the status of the innate immune response in the nasal epithelium of pregnant vs. non-pregnant female rats. IAV cell entry factors — sialic acid [SA] α-2,3- and α-2,6-linked glycans for avian and human IAV, respectively — were detected and quantified with lectin-based immunoblotting and flow cytometry. Baseline frequencies of innate immune cell phenotypes in single cell suspensions of the nasal epithelium were studied with flow cytometry. Subsequently, the magnitude of interferon and cytokine responses was studied with ELISA and cytokine arrays after intranasal resiquimod, a Toll-like receptor 7/8 agonist that mimics IAV infection. We noted substantially increased expression of cell entry factors for both avian and human IAV in the nasal epithelium during pregnancy. Assessment of the innate immune state of the nasal epithelium during pregnancy revealed two previously unreported features: (i) increased presence of tissue-resident plasmacytoid dendritic cells, and (ii) markedly enhanced release of interferon-α but not of the other interferons or cytokines 2 h after intranasal resiquimod. Collectively, our findings challenge the conventional notion of pregnancy-induced immunosuppression as a cause for severe influenza A disease and suggest the need for focused studies on viral tropism during pregnancy to better understand the proximate cause for the observed immunopathology.

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.

Feasibility of establishing a Canadian Obstetric Survey System (CanOSS) for severe maternal morbidity: a study protocol

INTRODUCTION

Severe maternal morbidity (SMM)-an unexpected pregnancy-associated maternal outcome resulting in severe illness, prolonged hospitalisation or long-term disability-is recognised by many, as the preferred indicator of the quality of maternity care, especially in high-income countries. Obtaining comprehensive details on events and circumstances leading to SMM, obtained through maternity units, could complement data from large epidemiological studies and enable targeted interventions to improve maternal health. The aim of this study is to assess the feasibility of gathering such data from maternity units across Canadian provinces and territories, with the goal of establishing a national obstetric survey system for SMM in Canada.

METHODS AND ANALYSIS

We propose a sequential explanatory mixed-methods study. We will first distribute a cross-sectional survey to leads of all maternity units across Canada to gather information on (1) Whether the unit has a system for reviewing SMM and the nature and format of this system, (2) Willingness to share anonymised data on SMM by direct entry using a web-based platform and (3) Respondents' perception on the definition and leading causes of SMM at a local level. This will be followed by semistructured interviews with respondent groups defined a priori, to identify barriers and facilitators for data sharing. We will perform an integrated analysis to determine feasibility outcomes, a narrative description of barriers and facilitators for data-sharing and resource implications for data acquisition on an annual basis, and variations in top-5 causes of SMM.

ETHICS AND DISSEMINATION

The study has been approved by the Mount Sinai and Hamilton Integrated Research Ethics Boards. The study findings will be presented at annual scientific meetings of the Society of Obstetricians and Gynaecologists of Canada, North American Society of Obstetric Medicine, and International Network of Obstetric Survey Systems and published in an open-access peer-reviewed Obstetrics and Gynaecology or General Internal Medicine journal.