Pregnancy as a risk factor for severe outcomes from influenza virus infection: A systematic review and meta-analysis of observational studies

Influenza virus-related critical illness: prevention, diagnosis, treatment

Annual seasonal influenza epidemics of variable severity result in significant morbidity and mortality in the United States (U.S.) and worldwide. In temperate climate countries, including the U.S., influenza activity peaks during the winter months. Annual influenza vaccination is recommended for all persons in the U.S. aged 6 months and older, and among those at increased risk for influenza-related complications in other parts of the world (e.g. young children, elderly). Observational studies have reported effectiveness of influenza vaccination to reduce the risks of severe disease requiring hospitalization, intensive care unit admission, and death. A diagnosis of influenza should be considered in critically ill patients admitted with complications such as exacerbation of underlying chronic comorbidities, community-acquired pneumonia, and respiratory failure during influenza season. Molecular tests are recommended for influenza testing of respiratory specimens in hospitalized patients. Antigen detection assays are not recommended in critically ill patients because of lower sensitivity; negative results of these tests should not be used to make clinical decisions, and respiratory specimens should be tested for influenza by molecular assays. Because critically ill patients with lower respiratory tract disease may have cleared influenza virus in the upper respiratory tract, but have prolonged influenza viral replication in the lower respiratory tract, an endotracheal aspirate (preferentially) or bronchoalveolar lavage fluid specimen (if collected for other diagnostic purposes) should be tested by molecular assay for detection of influenza viruses.Observational studies have reported that antiviral treatment of critically ill adult influenza patients with a neuraminidase inhibitor is associated with survival benefit. Since earlier initiation of antiviral treatment is associated with the greatest clinical benefit, standard-dose oseltamivir (75 mg twice daily in adults) for enteric administration is recommended as soon as possible as it is well absorbed in critically ill patients. Based upon observational data that suggest harms, adjunctive corticosteroid treatment is currently not recommended for children or adults hospitalized with influenza, including critically ill patients, unless clinically indicated for another reason, such as treatment of asthma or COPD exacerbation, or septic shock. A number of pharmaceutical agents are in development for treatment of severe influenza.

Influenza virus-related critical illness: prevention, diagnosis, treatment

Annual seasonal influenza epidemics of variable severity result in significant morbidity and mortality in the United States (U.S.) and worldwide. In temperate climate countries, including the U.S., influenza activity peaks during the winter months. Annual influenza vaccination is recommended for all persons in the U.S. aged 6 months and older, and among those at increased risk for influenza-related complications in other parts of the world (e.g. young children, elderly). Observational studies have reported effectiveness of influenza vaccination to reduce the risks of severe disease requiring hospitalization, intensive care unit admission, and death. A diagnosis of influenza should be considered in critically ill patients admitted with complications such as exacerbation of underlying chronic comorbidities, community-acquired pneumonia, and respiratory failure during influenza season. Molecular tests are recommended for influenza testing of respiratory specimens in hospitalized patients. Antigen detection assays are not recommended in critically ill patients because of lower sensitivity; negative results of these tests should not be used to make clinical decisions, and respiratory specimens should be tested for influenza by molecular assays. Because critically ill patients with lower respiratory tract disease may have cleared influenza virus in the upper respiratory tract, but have prolonged influenza viral replication in the lower respiratory tract, an endotracheal aspirate (preferentially) or bronchoalveolar lavage fluid specimen (if collected for other diagnostic purposes) should be tested by molecular assay for detection of influenza viruses.Observational studies have reported that antiviral treatment of critically ill adult influenza patients with a neuraminidase inhibitor is associated with survival benefit. Since earlier initiation of antiviral treatment is associated with the greatest clinical benefit, standard-dose oseltamivir (75 mg twice daily in adults) for enteric administration is recommended as soon as possible as it is well absorbed in critically ill patients. Based upon observational data that suggest harms, adjunctive corticosteroid treatment is currently not recommended for children or adults hospitalized with influenza, including critically ill patients, unless clinically indicated for another reason, such as treatment of asthma or COPD exacerbation, or septic shock. A number of pharmaceutical agents are in development for treatment of severe influenza.

Challenges in estimating influenza vaccine effectiveness

Introduction: Influenza vaccination is regarded as the most effective way to prevent influenza infection. Due to the rapid genetic changes that influenza viruses undergo, seasonal influenza vaccines must be reformulated and re-administered annually necessitating the evaluation of influenza vaccine effectiveness (VE) each year. The estimation of influenza VE presents numerous challenges. Areas Covered: This review aims to identify, discuss, and, where possible, offer suggestions for dealing with the following challenges in estimating influenza VE: different outcomes of interest against which VE is estimated, study designs used to assess VE, sources of bias and confounding, repeat vaccination, waning immunity, population level effects of vaccination, and VE in at-risk populations. Expert Opinion: The estimation of influenza VE has improved with surveillance networks, better understanding of sources of bias and confounding, and the implementation of advanced statistical methods. Future research should focus on better estimates of the indirect effects of vaccination, the biological effects of vaccination, and how vaccines interact with the immune system. Specifically, little is known about how influenza vaccination impacts an individual's infectiousness, how vaccines wane over time, and the impact of repeated vaccination.

Influenza epidemiology and influenza vaccine effectiveness during the 2015-2016 season: results from the Global Influenza Hospital Surveillance Network

BACKGROUND

The Global Influenza Hospital Surveillance Network is an international platform whose primary objective is to study severe cases of influenza requiring hospitalization.

METHODS

During the 2015-2016 influenza season, 11 sites in the Global Influenza Hospital Surveillance Network in nine countries (Russian Federation, Czech Republic, Turkey, France, China, Spain, Mexico, India, and Brazil) participated in a prospective, active-surveillance, hospital-based epidemiological study. Influenza infection was confirmed by reverse transcription-polymerase chain reaction. Influenza vaccine effectiveness (IVE) against laboratory-confirmed influenza was estimated using a test-negative approach.

RESULTS

9882 patients with laboratory results were included of which 2415 (24.4%) were positive for influenza, including 1415 (14.3%) for A(H1N1)pdm09, 235 (2.4%) for A(H3N2), 180 (1.8%) for A not subtyped, 45 (0.5%) for B/Yamagata-lineage, 532 (5.4%) for B/Victoria-lineage, and 33 (0.3%) for B not subtyped. Of included admissions, 39% were < 5 years of age and 67% had no underlying conditions. The odds of being admitted with influenza were higher among pregnant than non-pregnant women (odds ratio, 2.82 [95% confidence interval (CI), 1.90 to 4.19]). Adjusted IVE against influenza-related hospitalization was 16.3% (95% CI, 0.4 to 29.7). Among patients targeted for influenza vaccination, adjusted IVE against hospital admission with influenza was 16.2% (95% CI, - 3.6 to 32.2) overall, 23.0% (95% CI, - 3.3 to 42.6) against A(H1N1)pdm09, and - 25.6% (95% CI, - 86.3 to 15.4) against B/Victoria lineage.

CONCLUSIONS

The 2015-2016 influenza season was dominated by A(H1N1)pdm09 and B/Victoria-lineage. Hospitalization with influenza often occurred in healthy and young individuals, and pregnant women were at increased risk of influenza-related hospitalization. Influenza vaccines provided low to moderate protection against hospitalization with influenza and no protection against the predominant circulating B lineage, highlighting the need for more effective and broader influenza vaccines.

Racial disparities in U.S. maternal influenza vaccine uptake: Results from analysis of Pregnancy Risk Assessment Monitoring System (PRAMS) data, 2012-2015

BACKGROUND

Pregnant women are at increased risk of hospitalization, serious complications, poor pregnancy outcomes, and mortality from influenza. Prior research suggests that there are racial/ethnic disparities in vaccination coverage and that a healthcare provider vaccination recommendation is associated with significantly higher vaccine uptake than without such a recommendation. The purpose of this study is to examine racial/ethnic disparities in healthcare providers' recommendations for pregnant women to receive the influenza vaccine and in vaccine uptake.

METHODS

This cross-sectional population-based study analyzed data from the Centers for Disease Control and Prevention's Pregnancy Risk Assessment Monitoring System (PRAMS) during 2012-2015 (n = 130161). Both healthcare provider recommendation and vaccine uptake were assessed dichotomously. Logistic regression was conducted to ascertain adjusted odds ratios and 95% confidence intervals, controlling for maternal age, marital status, education, prenatal care utilization, and smoking status.

RESULTS

Influenza vaccine uptake during pregnancy ranged from 39.1% among non-Hispanic (NH) Black women to 55.4% among NH Asian women. In the adjusted analysis, NH Black and NH Asian women had 19% (95% CI 0.75-0.86) and 34% (95% CI 0.61-0.72) decreased odds of receiving a provider recommendation for influenza vaccine during pregnancy, respectively, compared to NH White women. For influenza vaccine uptake, NH Black women were 30% less likely (95% CI 0.65-0.74) to receive influenza vaccine during pregnancy compared to NH White women.

CONCLUSIONS

Our findings indicate that there are racial/ethnic disparities in healthcare provider recommendation and influenza vaccine uptake among pregnant women in the United States. Targeted efforts toward providers and interventions focusing on pregnant women may be warranted to reduce the disparity.

Obesity worsens the outcome of influenza virus infection associated with impaired type I interferon induction in mice

Increasing evidence indicates that obesity is a risk factor for increased severity of influenza virus infection. However, its precise immunological mechanism is not fully understood. To investigate this, diet-induced obese (DIO) mice were established by feeding C57BL/6 male mice a high-fat diet for 16 weeks. DIO and lean control mice were infected intranasally with 3000 pfu of influenza A virus (IAV) (PR8/H1N1). Interestingly, we found adipose tissue located along the bronchus in naïve DIO mice. In addition, the Nos2 level was significantly higher and Arg1 level was significantly lower in lung macrophages of naïve DIO mice, consistent with an M1-skewed phenotype. The survival rate and body weight of DIO mice infected with IAV were significantly lower than those of lean control mice and associated with higher viral load in the lungs of DIO mice. Histopathological analysis demonstrated higher numbers of inflammatory cells in the lungs of DIO mice after IAV infection. Levels of cytokines, including TNF-α, IL-6, IL-10, and type I IFN (IFN-α and IFN-β), in bronchoalveolar lavage fluid (BALF) were altered after IAV infection; in particular, IFN-α and IFN-β levels were significantly suppressed in the BALF of DIO mice. In vitro, bone marrow-derived macrophages were stimulated with ligands of toll-like receptor (TLR) 7/8, a pattern recognition receptor for single-stranded RNA, and levels of TNF-α, IL-6, and IL-10 were similarly altered. In addition, levels of IFN-α and IFN-β were significantly lower in culture supernatants of alveolar macrophages sorted from naïve DIO mice and infected with IAV, compared to those in macrophages sorted from lean control mice. Collectively, these results suggest that macrophages may be the main contributors to poor outcomes of influenza virus infection in obesity.

Progress and Remaining Gaps in Estimating the Global Disease Burden of Influenza

Influenza has long been a global public health priority because of the threat of another global pandemic. Although data are available for the annual burden of seasonal influenza in many developed countries, fewer disease burden data are available for low-income and tropical countries. In recent years, however, the surveillance systems created as part of national pandemic preparedness efforts have produced substantial data on the epidemiology and impact of influenza in countries where data were sparse. These data are leading to greater interest in seasonal influenza, including implementation of vaccination programs. However, a lack of quality data on severe influenza, nonrespiratory outcomes, and high-risk groups, as well as a need for better mathematical models and economic evaluations, are some of the major gaps that remain. These gaps are the focus of multilateral research and surveillance efforts that will strengthen global efforts in influenza control in the future.

Pulmonary complications of influenza infection: a targeted narrative review

Severe influenza infection represents a leading cause of global morbidity and mortality. Several clinical syndromes that involve a number of organs may be associated with Influenza infection. However, lower respiratory complications remain the most common and serious sequel of influenza infection. These include influenza pneumonia, superinfection with bacteria and fungi, exacerbation of underlying lung disease and ARDS. This review analyzes the available literature on the epidemiology and clinical considerations of these conditions. It also provides an overview of the effects of type of influenza, antiviral therapy, vaccination and other therapies on the outcome of these complications.

H1N1 Infection in Pregnancy; A Retrospective Study of Feto-Maternal Outcome and Impact of the Timing of Antiviral Therapy

Background and Objective

H1N1 infection carries an increased risk in pregnancy. Our aim was to study the feto-maternal outcome and the effect of early initiation of therapy.

Methods

This is a retrospective descriptive study. Confirmed infected cases were included. Maternal age, parity, gestational age at diagnosis, presenting symptoms, the time between presentation and starting therapy, ICU admission, and maternal and perinatal outcome were evaluated.

Results

Nineteen confirmed patients were included. Most patients are 31 years old or more. Multiparous patients were 73.68%, and 57.89% were in the third trimester. Most of our patients presented with cough, fever, and chills. Two patients were admitted to the ICU. One of them was a case of maternal mortality. 42.10% of patients were started on therapy only one day after the clinical onset of symptoms. 26.31% delivered before 37 completed weeks. 73.68% delivered beyond term. Around one third delivered vaginally. 45% of babies weighed more than 3 kg. Four babies weighed less than 2 kg. Ninety percent had APGAR scores more than 8 at 1 and 5 minutes after delivery. Twenty-five percent were admitted to the NICU with no neonatal mortalities.

Conclusions

H1N1 influenza A infection in pregnancy is associated with adverse maternal and perinatal outcomes. Medical and public awareness, low threshold for testing suspected pregnant patients, very early initiation of antiviral therapy, and a multidisciplinary approach in our series decreased the overall adverse effects of this infection.

Knowledge about influenza and adherence to the recommendations for influenza vaccination of pregnant women after an educational intervention in Greece

Pregnant women and young infants are at increased risk for influenza-associated severe disease, complications and hospitalizations. In Greece influenza vaccination during pregnancy remains extremely low. We studied the knowledge about influenza and the adherence to the recommendations for influenza vaccination of pregnant women following an educational intervention in a large maternity hospital. A standardized questionnaire was used. A knowledge score was calculated for each woman. A total of 304 pregnant women were studied [mean age: 31.5 years (standard deviation (SD): 5.4 years), mean gestational age: 27.8 weeks (SD: 9.6 weeks)]. Their mean knowledge score was 87%. Sixty pregnant women (19.5%) were vaccinated against influenza at a mean gestational age of 24.6 weeks (SD: 7.5 weeks). Multiple regression analysis revealed that previous influenza vaccination and information about the need to get vaccinated were the only significant factors associated with an increased probability for influenza vaccination during pregnancy (47% versus 17% in women with and without a history of influenza vaccination in the past, respectively; odds ratio = 3.6; p-value = 0.016, and 32% versus 4% in women informed compared to those uninformed about the need for vaccination during pregnancy, respectively; odds ratio = 17.8; p-value<0.001). Seventy women provided a reason for refusing influenza vaccination. "Fear of adverse events" (for them or the fetus) was the prevalent reason for refusing influenza vaccination (19 women; 27%), followed by the statements "influenza vaccination is not necessary" (13; 18.5%) and "not at risk to get influenza" (9; 13%). In conclusion, an educational intervention was associated with an influenza vaccination rate of 19.5% among pregnant women compared to <2% the past years. In order to improve vaccine uptake by pregnant women and protect them and their babies, more intensified interventions should be explored.

Seasonal influenza vaccination policies in the Eastern Mediterranean Region: Current status and the way forward

BACKGROUND

The World Health Organization recommends annual influenza vaccination, especially in high-risk groups. Little is known about the adoption and implementation of influenza vaccination policies in the Eastern Mediterranean Region.

METHODS

A survey was distributed to country representatives at the ministries of health of the 22 countries of the Region between December 2016 and February 2017 to capture data on influenza immunization policies, recommendations, and practices in place.

RESULTS

Of the 20 countries that responded to the survey, 14 reported having influenza immunization policies during the 2015/2016 influenza season. All countries with an influenza immunization policy recommended vaccination for people with chronic medical conditions, healthcare workers and pilgrims. Two of the 20 countries did not target pregnant women. Eight countries used the northern hemisphere formulation, one used the southern hemisphere formulation and nine used both. Vaccination coverage was not monitored by all countries and for all target groups. Where reported, coverage of a number of target groups (healthcare workers, children) was generally low. Data on the burden of influenza and vaccine protection are scarce in the Region.

CONCLUSIONS

Despite widespread policy recommendations on influenza vaccination, attaining high coverage rates remains a challenge in the Eastern Mediterranean Region. Tackling disparities in influenza vaccine accessibility and strengthening surveillance systems may increase influenza vaccine introduction and use.

Epidemiology of influenza in pregnant women hospitalized with respiratory illness in Moscow, 2012/2013-2015/2016: a hospital-based active surveillance study

Background

To better understand the impact of seasonal influenza in pregnant women we analyzed data collected during four seasons at a hospital for acute respiratory infection that specializes in treating pregnant women.

Methods

This was a single-center active surveillance study of women 15–44 years of age hospitalized for acute respiratory diseases between 2012/2013 and 2015/2016 in Moscow, Russian Federation. Women had to have been hospitalized within 7 days of the onset of symptoms. Swabs were taken within 48 h of admission, and influenza was detected by reverse transcription-polymerase chain reaction.

Results

During the four seasons, of the 1992 hospitalized women 1748 were pregnant. Laboratory-confirmed influenza was detected more frequently in pregnant women (825/1748; 47.2%) than non-pregnant women (58/244; 23.8%) (OR for influenza = 2.87 [95% CI, 2.10–3.92]; p <  0.001). This pattern was homogenous across seasons (p = 0.112 by test of homogeneity of equal odds). Influenza A(H1N1)pdm09 was the dominant strain in 2012/2013, A(H3N2) in 2013/2014, B/Yamagata lineage and A(H3N2) in 2014/2015, and A(H1N1)pdm09 in 2015/2016. Influenza-positive pregnant admissions went to the hospital sooner than influenza-negative pregnant admissions (p <  0.001). The risk of influenza increased by 2% with each year of age and was higher in women with underlying conditions (OR = 1.52 [95% CI, 1.16 to 1.99]). Pregnant women positive for influenza were homogeneously distributed by trimester (p = 0.37 for homogeneity; p = 0.49 for trend). Frequencies of stillbirth, delivery, preterm delivery, and caesarean delivery did not significantly differ between influenza-positive and influenza-negative hospitalized pregnant women or between subtypes/lineages.

Conclusions

Pregnant women are at increased risk for hospitalization due to influenza irrespective of season, circulating viruses, or trimester.

Electronic supplementary material

The online version of this article (10.1186/s12884-019-2192-z) contains supplementary material, which is available to authorized users.

Burden, effectiveness and safety of influenza vaccines in elderly, paediatric and pregnant populations

Vaccination is the most practical means available for preventing influenza. Influenza vaccines require frequent updates to keep pace with antigenic drift of the virus, and the effectiveness, and sometimes the safety, of the vaccine can therefore vary from season to season. Three key populations that the World Health Organization recommends should be prioritized for influenza vaccination are pregnant women, children younger than 5 years of age and the elderly. This review discusses the burden of influenza and the safety and effectiveness profile of influenza vaccines recommended for these groups.

Key considerations for successful implementation of maternal immunization programs in low and middle income countries

The Maternal Neonatal Tetanus Elimination program is proof of concept for the feasibility and potential for maternal immunization to reduce neonatal mortality particularly in low and middle-income countries. Introduction of any additional vaccine into the antenatal space, such as Influenza and Pertussis, and potentially Respiratory Syncytial Virus and Group B Streptococcus vaccines in the future, requires strengthening of antenatal care and immunization services. Successful implementation also requires robust disease surveillance in pregnant women and neonates and active surveillance for adverse events following immunization to monitor the impact and ensure the safe use of the vaccine. This review outlines five key elements essential for successful implementation of a maternal immunization program focusing particularly on low and middle-income countries. These include; relevant considerations in supporting a decision to undertake a maternal immunization program including knowledge of local disease epidemiology, involvement of the consumer, healthcare provider recommendation, equitable access to maternal vaccination, and systems for disease surveillance, program evaluation and safety monitoring.

Adult Immunization - Need of the Hour

Immunization is the process of making individuals immune. Childhood immunization is a common process for various aliments, but adult immunization in the Indian scenario is obscure. Officially, India has been declared polio-free, which is an achievement despite cultural, political, economic, geographic, and so many other factors. The changing demographics of adult, geriatric population and growing cost of health-care maintenance are a concern in developing countries like India. Thus, promoting healthy lifestyle needs prevention, early detection, and management of various diseases and disorders. Certainly, prevention in adults is yet to be tapped completely, so that goal of 100% prevention can be achieved. Various fraternities of medical association have come up with guidelines for adult immunization schedules in India. The present paper reviews infectious diseases such as anthrax, chikungunya, cholera, dengue, influenza, and malaria in this section of the review. We humbly request all health-care professionals and educators to educate the mass for adult immunization. So that, cost involved for treatment and workforce for the management of diseases can be better utilized in some other needed areas.

Characteristics and pregnancy outcomes of patients with severe pneumonia complicating pregnancy: a retrospective study of 12 cases and a literature review

Background

Pneumonia during pregnancy has been proven to be associated with increased maternal and fetal morbidity and mortality. The management of severe pneumonia in gravid patients is even more challenging. Thus, we summarized the characteristics and pregnancy outcomes of these patients and explored the probable risk factors and predictive factors for pneumonia during pregnancy and the appropriate timing of delivery in severe pneumonia patients.

Methods

A retrospective cohort study was conducted with 12 patients who were diagnosed with severe pneumonia complicating pregnancy at Peking Union Medical College Hospital between January 2010 and June 2017. The clinical features, treatment strategies, and pregnancy outcomes were collected from medical records and telephone calls.

Results

All 12 patients were in their late second or third trimester. The patients had a higher prevalence of anemia (50%) and preeclampsia (25%) than ordinary pregnant women. Delayed diagnoses were not uncommon. Two mothers died in our series, resulting in a mortality rate of 17%. Two intrauterine deaths were observed. Elective delivery was not performed in any of the four patients in their second trimester. Six of the seven patients who presented after 28 weeks of gestation and had live fetuses underwent emergency deliveries. Preterm births (6/7) and cesarean sections (5/7) were the two leading adverse outcomes in newborns.

Conclusions

Anemia, advanced gestational age, and preeclampsia might be associated with the severity of pneumonia. Chest radiographs should be taken as soon as pneumonia is highly suspected to facilitate an early diagnosis. High incidences of adverse fetal outcomes were observed; thus, termination of the pregnancy is recommended for patients in their third trimester when respiratory function deteriorates progressively. However, it might be reasonable to continue pregnancy for those in their first or second trimester.

Risk of pregnancy complications and adverse birth outcomes after maternal A(H1N1)pdm09 influenza: a Norwegian population-based cohort study

Background

The effects of maternal influenza infection on the fetus remain unclear. We studied mild influenza and influenza antibodies in relation to birth weight and risks of pre-eclampsia, preterm birth (PTB), and small for gestational age (SGA) birth among the unvaccinated participants in the Norwegian Influenza Pregnancy Cohort.

Methods

Pregnant women attending a routine ultrasound were recruited from four hospitals in Norway shortly after the 2009 A(H1N1) pandemic. The present study was restricted to unvaccinated participants who were pregnant during the pandemic. Information on the participants was obtained through questionnaires and linkage with national registries. Maternal blood samples were collected at delivery. Women with laboratory-confirmed A(H1N1)pdm09 influenza, a clinical diagnosis of influenza, or self-reported influenza during the pandemic were classified as having had influenza. A(H1N1)pdm09-specific antibodies in serum were detected with the hemagglutination-inhibition assay. Detection of antibodies was considered an indicator of infection during the pandemic in the unvaccinated participants. Odds ratios were estimated with logistic regression. Quantile regression was used to estimate differences in the distribution of birth weight.

Results

Among the 1258 women included in this study, there were 37 cases of pre-eclampsia, 41 births were PTB, and 103 births were SGA. 226 women (18.0%) had influenza during the pandemic. The majority of cases did not receive medical care, and only a small proportion (1.3%) of the cases were hospitalized. Thus, the cases consisted primarily of women with mild illness. No significant associations between influenza and risk of pre-eclampsia, PTB, or SGA birth were observed. Detection of A(H1N1)pdm09-specific antibodies was associated with a lower 10th percentile of birth weight, β = − 159 g (95% CI − 309, − 9).

Conclusions

Mild influenza illness during pregnancy was not associated with increased risk of pre-eclampsia, PTB or SGA birth. However, influenza infection during pregnancy may reduce the birth weight of the smallest children.

Exploring the risk of severe outcomes and the role of seasonal influenza vaccination in pregnant women hospitalized with confirmed influenza, Spain, 2010/11-2015/16

Based on previous observations during pandemics and seasonal epidemics, pregnant women are considered at risk of developing severe influenza outcomes after influenza infection. With the aim of preventing severe influenza illness, the World Health Organization (WHO) includes pregnant women as a target group for seasonal influenza vaccination. However, influenza vaccine uptake during pregnancy remains low in many countries, including Spain. The objectives of this study were to increase the evidence of pregnancy as a risk factor for severe influenza illness and to study the potential role of seasonal influenza vaccination in the prevention of severe outcomes in infected pregnant women. Using information from the surveillance of Severe Hospitalized Confirmed Influenza Cases (SHCIC) in Spain, from seasons 2010/11 to 2015/16, we estimated that pregnant women in our study had a relative risk of hospitalization with severe influenza nearly 7.8 times higher than non-pregnant women of reproductive age. Only 5 out of 167 pregnant women with known vaccination status in our study had been vaccinated (3.6%). Such extremely low vaccination coverage only allowed obtaining crude estimates suggesting a protective effect of the vaccine against influenza complications (ICU admission or death). Our overall results support that pregnant women could benefit from seasonal influenza vaccination, in line with national and international recommendations.

Knowledge, attitudes and practices about influenza vaccination among pregnant women and healthcare providers serving pregnant women in Managua, Nicaragua

BACKGROUND

Nicaragua implemented an influenza vaccination program for pregnant women with high-risk obstetric conditions in 2007. In 2014, the recommendation of influenza vaccination expanded to include all pregnant women. Given the expansion in the recommendation of vaccination, we evaluated knowledge, attitudes and practices of pregnant women and their healthcare providers towards influenza vaccination and its recommendation.

METHODS

We conducted surveys among pregnant women and their healthcare providers from June to August 2016 at two hospitals and 140 health facilities in Managua. The questions were adapted from the U.S. national CDC influenza survey and related to knowledge, attitudes and practices about influenza vaccination and barriers to vaccination. We analyzed reasons for not receiving vaccination among pregnant women as well as receipt of vaccination recommendation and offer by their healthcare providers.

RESULTS

Of 1,303 pregnant women enrolled, 42% (5 4 5) reported receiving influenza vaccination in the 2016 season. Of those who reported not receiving vaccination, 46% indicated barriers to vaccination. Pregnant women who were vaccinated were more likely to be aware of the recommendation for vaccination and the risks of influenza illness during pregnancy and to perceive the vaccine as safe and effective, compared to unvaccinated pregnant women (p-values < 0.001). Of the 619 health workers enrolled, over 89% recalled recommending influenza vaccination to all pregnant women, regardless of obstetric risk. Of the 1,223 women who had a prenatal visit between the start date of the influenza vaccination and the time of interview, 44% recalled receiving a recommendation for influenza vaccination and 43% were offered vaccination. Vaccination rates were higher for those receiving a recommendation and offer of vaccination compared with those who received neither (95% vs 5%, p-value < 0.001).

CONCLUSION

Pregnant women in Managua had positive perceptions of influenza vaccine and were receptive to receiving influenza vaccination, especially after the offer and recommendation by their healthcare providers.

Influenza immunization of pregnant women in resource-constrained countries: an update for funding and implementation decisions

PURPOSE OF REVIEW

In 2018, Gavi, the Vaccine Alliance, is expected to review the strategy of maternal influenza immunization for potential investment in low-income countries.

RECENT FINDINGS

Clinical trial data confirm the efficacy of maternal influenza immunization to prevent influenza disease in both mothers and their infants during the first months of life. Trial and observational data indicate no significant adverse events in mothers or newborns. High-quality disease burden data, particularly for seasonal influenza in low-income and middle-income countries, are limited. Thus, the anticipated impact of maternal influenza immunization programs on severe illness is unclear. However, assessments of the public health value of investment in maternal influenza immunization should extend beyond calculations of disease prevention and include broader effects such as improving health systems for antenatal care delivery, preventing inappropriate antibacterial prescribing, building a platform for other vaccines to be used during pregnancy, and strengthening systems to regulate, procure, and distribute influenza vaccines in response to a future pandemic.

SUMMARY

A global investment in a maternal influenza immunization strategy would prevent influenza disease in pregnant women and their infants. It would also provide additional public health value by strengthening antenatal care systems and improving country pandemic preparedness.

Influenza immunization policies: Which could be the main reasons for differences among countries?

Despite the availability of effective prophylactic and therapeutic measures, influenza remains one of the most important infectious disease threats to the human population. Every year, seasonal influenza epidemics infect up to 30% of the population; a relevant portion of the ill are hospitalized, and more than a marginal number die. In an attempt to reduce the medical, social and economic burden of influenza, vaccines are recommended by many health authorities worldwide. However, not all countries have a national program for influenza immunization. The main aim of this paper is to list the differences among influenza immunization policies of various countries, highlighting the most important scientific reasons that may have led health authorities to make different decisions. The manuscript highlights that national influenza immunization policies can vary significantly from country to country. These differences arise from insufficient evidence of the relevance of influenza infection from a clinical, social and economic point of view. The lack of precise data on the true frequency and clinical relevance of influenza infection makes it nearly impossible to establish the economic burden of influenza. Moreover, it remains very difficult to evaluate the efficacy of the different influenza vaccines and whether their use is cost-effective considering the various types of people receiving them and the indirect advantages. Disparities among countries will be overcome only when more reliable data regarding all these aspects of influenza infection, particularly those related to the true impact of the disease, are precisely defined.

Epidemiology of seasonal influenza infection in pregnant women and its impact on birth outcomes

Seasonal influenza can cause significant morbidity in pregnant women. Much of the existing epidemiological evidence on influenza during pregnancy has focused on the 2009 A/H1N1 pandemic. To measure the epidemiological characteristics of seasonal influenza infection among pregnant women and the impact on infant health, a cohort of 86 779 pregnancies during the influenza season (2012-2014) was established using probabilistic linkage of notifiable infectious disease, hospital admission, and birth information. A total of 192 laboratory-confirmed influenza infections were identified (2·2 per 1000 pregnancies), 14·6% of which were admitted to hospital. There was no difference in the proportion of infections admitted to hospital by trimester or subtype of infection. Influenza B infections were more likely to occur in second trimester compared with influenza A/H3N2 and influenza A/H1N1 infections (41·3%, 23·6%, and 33·3%, respectively), and on average, infants born to women with influenza B during pregnancy had 4·0% (95% CI 0·3-7·6%) lower birth weight relative to optimal compared with infants born to uninfected women (P = 0·03). Results from this linked population-based study suggest that there are differences in maternal infection by virus type and subtype and support the provision of seasonal influenza vaccine to pregnant women.

Influenza epidemiology and immunization during pregnancy: Final report of a World Health Organization working group

From 2014 to 2017, the World Health Organization convened a working group to evaluate influenza disease burden and vaccine efficacy to inform estimates of maternal influenza immunization program impact. The group evaluated existing systematic reviews and relevant primary studies, and conducted four new systematic reviews. There was strong evidence that maternal influenza immunization prevented influenza illness in pregnant women and their infants, although data on severe illness prevention were lacking. The limited number of studies reporting influenza incidence in pregnant women and infants under six months had highly variable estimates and underrepresented low- and middle-income countries. The evidence that maternal influenza immunization reduces the risk of adverse birth outcomes was conflicting, and many observational studies were subject to substantial bias. The lack of scientific clarity regarding disease burden or magnitude of vaccine efficacy against severe illness poses challenges for robust estimation of the potential impact of maternal influenza immunization programs.

Preparing for Emerging Infectious Diseases in the Perinatal Population

The unprecedented scale of the 2014-2015 Ebola virus outbreak in West Africa and the recent emergence and rapid spread of Zika virus infection and resultant neonatal sequelae show that the geographic range, spread, and effect of emerging infections are unpredictable. Lessons learned from analyzing the response of an academic medical center to care for pregnant women with suspected or confirmed Ebola virus disease can help health care professionals address future threats from emerging infections.

Implementation of the Recommendation to Vaccinate Pregnant Women against Seasonal Influenza - Vaccination Rates and Acceptance

Introduction In Germany vaccination recommendations are revised annually and published by the Standing Committee on Vaccination at the Robert Koch Institute (STIKO). In 2010 the vaccination recommendations were amended to include the proposal that pregnant women in the 2nd trimester of pregnancy and pregnant women with additional underlying disease in the 1st trimester of pregnancy should be vaccinated against seasonal influenza. This paper reports on vaccination rates and the factors influencing them. Method A cross-sectional study was carried out in two level 1 perinatal centers in two different German federal states (Saarland and Rhineland-Palatinate) during the influenza seasons of 2012/2013 and 2013/2014. A total of 253 pregnant women were included in the study. Pregnant women were interviewed using a standardized, pre-tested questionnaire and asked whether they were aware of the recommendation to vaccinate against seasonal influenza and about possible factors which might influence their decision to be vaccinated. In addition, data from their vaccination certificates and pregnancy passports were evaluated. Results Overall, the records of only 19.5 % of the pregnant women showed that they had been vaccinated against influenza in pregnancy. Among the group of pregnant women who had a previous history of vaccinations against influenza the willingness to be vaccinated was high (43.3 %) and this figure was statistically significant. The vaccination rate was even higher (49.9 %) and even more statistically significant among pregnant women whose gynecologist or family physician had recommended that they should be vaccinated. In contrast, only 3.3 % of pregnant women who had not been given the recommendation to vaccinate by their physicians were vaccinated against influenza. Discussion The failure to recommend that pregnant women be vaccinated against influenza and women's lack of any previous experience of influenza vaccination were the main reasons for the inadequate influenza vaccination coverage in pregnancy. Conclusion One of the key points to increase the influenza vaccination rate is to intensify the counselling of the pregnant women through the gynecologist.

Report of the WHO technical consultation on the effect of maternal influenza and influenza vaccination on the developing fetus: Montreal, Canada, September 30-October 1, 2015

In 2012, the World Health Organization (WHO) released a position paper on influenza vaccination recommending that pregnant women have the highest priority for seasonal vaccination in countries where the initiation or expansion of influenza immunization programs is under consideration. Although the primary goal of the WHO recommendation is to prevent influenza illness in pregnant women, the potential benefits of maternal immunization in protecting young infants are also recognized. The extent to which maternal influenza vaccination may prevent adverse birth outcomes such as preterm birth or small-for-gestational-age birth, however, is unclear as available studies are in disagreement. To inform WHO about the empirical evidence relating to possible benefits of influenza vaccination on birth outcomes, a consultation of experts was held in Montreal, Canada, September 30-October 1, 2015. Presentations and discussions covered a broad range of issues, including influenza virus infection during pregnancy and its effect on the health of the mother and the fetus, possible biological mechanisms for adverse birth outcomes following maternal influenza illness, evidence on birth outcomes following influenza illness during pregnancy, evidence from both observational studies and randomized controlled trials on birth outcomes following influenza vaccination of pregnant women, and methodological issues. This report provides an overview of the presentations, discussions and conclusions.