2009 H1N1 influenza and pregnancy--5 years later

Establish a Pregnant Sow–Neonate Model to Assess Maternal Immunity of a Candidate Influenza Vaccine

While it is well appreciated that maternal immunity can provide neonatal protection, the contribution of maternal vaccination toward generating such immunity is not well characterized. In our previous work, we created a candidate influenza vaccine using our chimeric hemagglutinin (HA) construct, HA-129. The HA-129 was expressed as part of a whole-virus vaccine that was built on the A/swine/Texas/4199-2/98-H3N2 backbone to generate the recombinant virus TX98-129. The TX98-129 candidate vaccine has the ability to induce broadly protective immune responses against genetically diversified influenza viruses in both mice and nursery pigs. In the current study, we established a pregnant sow–neonate model to evaluate the maternal immunity induced by this candidate vaccine to protect pregnant sows and their neonatal piglets against influenza virus infection. In pregnant sows, the results consistently show that TX98-129 induced a robust immune response against the TX98-129 virus and the parental viruses that were used to construct HA-129. After challenge with a field strain of influenza A virus, a significant increase in antibody titers was observed in vaccinated sows at both 5 and 22 days post challenge (dpc). The challenge virus was detected at a low level in the nasal swab of only one vaccinated sow at 5 dpc. Evaluation of cytokine responses in blood and lung tissue showed that levels of IFN-α and IL-1β were increased in the lung of vaccinated sows at 5 dpc, when compared to unvaccinated pigs. Further analysis of the T-cell subpopulation in PBMCs showed a higher ratio of IFN-γ-secreting CD4+CD8+ and CD8+ cytotoxic T cells in vaccinated sows at 22 dpc after stimulation with either challenge virus or vaccine virus. Finally, we used a neonatal challenge model to demonstrate that vaccine-induced maternal immunity can be passively transferred to newborn piglets. This was observed in the form of both increased antibody titers and deceased viral loads in neonates born from immunized sows. In summary, this study provides a swine model system to evaluate the impact of vaccination on maternal immunity and fetal/neonatal development.

Vaccination in pregnancy against pertussis and seasonal influenza: key learnings and components from high-performing vaccine programmes in three countries: the United Kingdom, the United States and Spain

BACKGROUND

Pertussis and seasonal influenza are responsible for significant maternal, neonatal, and infant morbidity and mortality, but vaccine coverage rates (VCR) for both pertussis (administered as a tetanus, diphtheria, acellular pertussis [Tdap] vaccination) and seasonal influenza in pregnancy remain generally low. Only a small number of countries, including Spain, the United Kingdom (UK), and the United States (US), have high Tdap and seasonal influenza VCRs in pregnancy. The purpose of this study was to identify the key factors that contributed to the high VCRs observed in these countries.

METHODS

The experience from both Tdap and seasonal influenza vaccination programmes during pregnancy were documented in Spain, the UK, and the US using a three-step approach. A literature review yielded 157 publications, and a further 117 documents were selected through desk research. A published five-pillar VCR framework for influenza was amended to evaluate the specific contributing factors leading to high Tdap and seasonal influenza VCRs among pregnant women.

RESULTS

The analysis identified components that contributed to higher VCR in pregnant women across three different healthcare systems in Spain, UK, and US. The combination of several key interventions in each country led to a rapid increase in VCR that reached near-optimal levels (i.e. 75% for seasonal influenza) within a few years. As well as inclusion in national immunisation programme and vaccine reimbursement, key components that were identified included the mobilisation of health authorities, prenatal care Healthcare Professionals (HCP) and scientific societies, the inclusion of vaccination in antenatal medical guidance, the provision of educational material to HCPs, and a strong disease awareness driven by recent pertussis outbreaks in each country.

CONCLUSIONS

Although there is no simple, universal solution to improving sub-optimal VCRs, the list of components identified in this study from three countries with high-performing Tdap and seasonal influenza vaccination programmes provides a basis for public health and medical stakeholders in other countries to define strategies to successfully implement national vaccination programmes for pregnant women.

Society for Maternal-Fetal Medicine Consult Series #54: Assessing the risk of maternal morbidity and mortality

The rates of maternal morbidity and mortality in the United States demand a comprehensive approach to assessing pregnancy-related risks. Numerous medical and nonmedical factors contribute to maternal morbidity and mortality. Reducing the number of women who experience pregnancy morbidity requires identifying which women are at greatest risk and initiating appropriate interventions early in the reproductive life course. The purpose of this Consult is to educate all healthcare practitioners about factors contributing to a high-risk pregnancy, strategies to assess maternal health risks due to pregnancy, and the importance of risk assessment across the reproductive spectrum in reducing maternal morbidity and mortality.

Perinatal COVID-19: guideline development, implementation, and challenges

PURPOSE OF REVIEW

The aim of this review was to describe the process of and challenges in developing national guidance for management of infants born to mothers with COVID-19.

RECENT FINDINGS

Beginning in January 2020, infection with the novel coronavirus SARS-CoV-2 spread across the USA, causing the illness COVID-19. As pregnant women began to present for delivery while sick with COVID-19, the American Academy of Pediatrics (AAP) convened a writing group in March 2020 to develop guidance for the management of their newborns. The initial guidance was developed emergently and was forced to rely on extremely limited data from China. The initial guidance advocated for a conservative approach that included temporary physical separation of infected mother and newborn. To address the knowledge deficit, the AAP sponsored a volunteer registry to collect data on perinatal infection and management. As data have emerged informing the natural history of COVID-19, the performance of PCR-based diagnostics, the value of infection control measures and the risk of infant disease, AAP has issued serial updates to newborn guidance.

SUMMARY

Evolving knowledge on the epidemiology of perinatal COVID-19 has informed newborn guidance. The most recent guidance focuses on the use of infection control measures to support maternal-newborn contact and breastfeeding.

Clinical and computed tomographic (CT) images characteristics in the patients with COVID-19 infection: What should radiologists need to know?

OBJECTIVE

To evaluate the clinical and computed tomographic (CT) features in the patients with COVID-19 pneumonia confirmed by the real-time reverse transcriptase polymerase chain reaction (rRT-PCR) amplification of the viral DNA from a sputum sample.

MATERIAL AND METHODS

Clinical information and CT findings of a total of 14 patients with COVID-19 infection (age range, 12-83 years; females 6) were analyzed retrospectively. The clinical information includes the history of exposure, laboratory results, and the symptoms (such as fever, cough, headache, etc.); CT findings of chest include the extension and distribution of lesion, the ground-glass opacity (GGO), consolidation, bronchovascular enlarged, irregular linear appearances, pleural effusion, and lymphadenopathy.

RESULTS

Eight patients had the exposure history for recent travel to Wuhan of Hubei province (8/14, 57%), 6 had the exposure to patients with COVID-19 infection. Significant statistical differences were observed in lymphocyte percentage decreased and C-reactive protein elevated (p = 0.015). Seven patients had fever, 7 had cough, 2 had headache, 3 had fatigue, 1 had body soreness, 3 had diarrhea, and 2 had no obvious symptoms. In chest CT examination, 10 patients were positive (10/14, 71.43%). Among these patients, 9 had lesions involving both lungs (9/10, 90%), 8 had lesions involving 4 to 5 lobes (8/10, 80%). Most of lesions were distributed peripherally and the most significant lesions were observed in the right lower lobe in 9 patients (9/10, 90%). Nodules were observed in 5 patients (5/10, 50%); GGO, consolidation, and bronchovascular enlarged were shown in 9 patients (9/10, 90%); irregular linear appearances were revealed in 7 patients (7/10, 70%); and pleural effusions were exhibited in 2 patients (2/10, 20%). Last, no patients showed lymphadenopathy.

CONCLUSION

There were some typical CT features for diagnosis of COVID-19 pneumonia. The radiologists should know these CT findings and clinical information, which could help for accurate analysis in the patients with 2019 novel coronavirus infection.

Trend and spatial distribution of infectious diseases in pregnant women in the state of Paraná-Brazil

Objective

to analyze the trend and spatial distribution of some diseases that require compulsory notification in pregnant women.

Method

ecological study, with data from the National Notifiable Diseases Surveillance System, of the incidence of the six most frequent diseases that, require compulsory notification, in pregnant women. The Prais-Winsten model was used to analyze the trend classified as stable, decreasing and increasing, according to macro-regions. For the spatial analysis, the incidences distributed in percentiles, in choropleth maps, by Health Regions were calculated.

Results

the most frequent infections were syphilis, dengue, Human Immunodeficiency Virus, influenza, hepatitis and toxoplasmosis. Incidence increased by 30.8%, 30.4%, 15.4% and 2.6%, on average, for syphilis, toxoplasmosis, dengue and Human Immunodeficiency Virus, respectively. On average, the incidence of syphilis increased by 40.5% in Macro-regional North and 38% in Macro-regional Northwest. The spatial analysis showed, in the last four years, high incidence of dengue, syphilis and infection by Human Immunodeficiency Virus, which reached 180.2, 141.7 and 100.8 cases per 10,000 live births, respectively.

Conclusion

there were increased incidences of infection in pregnant women due to syphilis, toxoplasmosis and Human Immunodeficiency Virus, with differences in their spatial distribution, indicating that these diseases should be a priority in the care of pregnant women in more affected regions.

Randomized Quality Improvement Trial of Opting-In Versus Opting-Out to Increase Influenza Vaccination Rates during Pregnancy

Introduction  Despite strong recommendations, only 40.6% of pregnant women attending two prenatal clinics were vaccinated against influenza during the 2009 pandemic. We tested whether an opting-out approach would improve vaccine uptake. Methods  We conducted a randomized quality improvement (QI) trial to compare opting-out with conventional opting-in consent for influenza immunization. Women age ≥ 18 years attending the University of Texas Health Science Center at Houston (UTHealth) or UT-Medical Branch (UTMB) prenatal clinics during the 2010-2011 influenza season, were eligible. Results  We enrolled 280 women (140 UTHealth, 140 UTMB). Both groups had similar mean age (26.0 ± 5.5 years), mean gestational age (19.4 ± 9.5 weeks), and percent with underlying health conditions (20.7%). Vaccination rates with opting-in and opting-out were similar among all (83 vs. 84%), UTHealth (87 vs. 93%), and UTMB patients (79 vs.76%) ( p  > 0.05). In subsamples of patients assessed, consent strategy did not significantly affect maternal recall of information provided. Conclusion  While prenatal influenza vaccination uptake doubled from the 2009-2010 influenza season, opting-out did not perform better than opting-in, a conclusion opposite that we would have reached had this been a nonconcurrent trial. Vaccination rates dropped posttrial; hence, continued research is needed to increase the prenatal influenza immunizations.

Hospitalization during pregnancy according to childbirth financial coverage: a population-based study

Objective To analyze the occurrence, profile and main causes of hospitalization during pregnancy according to the type of childbirth financial coverage. Method A cross-sectional population-based study carried out with puerperal women through a stratified sample, calculated according to the hospital and the type of childbirth financial coverage source: public sector (SUS) or private (not SUS). The sociodemographic profile, the rate of obstetric complications and the causes of hospitalization were analyzed, coded according to International Classification of Diseases. Results A total of 928 postpartum women were interviewed, of whom 32.2% reported at least one hospitalization during pregnancy. Those with childbirth covered by SUS were less favored because they were the majority among hospitalized women (57.2%), with a higher percentage of adolescents (18.1%), lower education level (91.8%), low family income (39.3%) and fewer prenatal consultations (25.3%). The most frequent causes of hospitalization were "other maternal diseases that complicate pregnancy" (24.6%) (with emphasis on anemia and influenza), urinary tract infection (13.1%), preterm labor (8.7%) and hypertension (7.2%). Conclusion Anemia, influenza, urinary tract infection, preterm labor and hypertension should especially be prevented and treated to avoid hospital admissions during pregnancy, especially among pregnant women covered by SUS.

Beyond the verbal: Pregnant women's preferences for receiving influenza and Tdap vaccine information from their obstetric care providers

OBJECTIVE

Prenatal providers are pregnant women's most trusted sources of health information, and a provider's recommendation is a strong predictor of maternal vaccine receipt. However, other ways women prefer receiving vaccine-related information from prenatal providers, aside from face-to-face conversations, is unclear. This study explores what secondary communication methods are preferred for receiving maternal vaccine-related information.

STUDY DESIGN

Obstetric patients at four prenatal clinics around Atlanta, Georgia received a 27-item survey between May 5th, 2016 and June 15th, 2016. Participants were asked about sources they currently use to obtain prenatal health information and their preferences for receiving vaccine-related information from providers. Descriptive statistics were calculated and chi-square tests were used to evaluate associations between participant characteristics and outcomes.

RESULTS

Women primarily reported using the CDC website (57.7%) and pregnancy-related websites (53.0%) to obtain vaccine information. Apart from clinical conversations, educational brochures (64.9%) and e-mails (54.7%) were the preferred methods of receiving vaccine information from providers, followed by their provider's practice website (42.1%). Communication preferences and interest in maternal immunization varied by race/ethnicity, age and education; white women were twice as likely to want information on a provider's practice website compared to African-American women (OR = 2.06; 95% CI: 1.31, 3.25).

CONCLUSIONS

Pregnant women use the Internet for information about vaccines, but they still value input from their providers. While e-mails and brochures were the preferred secondary modes of receiving information, a provider's existing practice website offers a potential communications medium that capitalizes on women's information seeking behaviors and preferences while limiting burden on providers.

Perspectives on benefit-risk decision-making in vaccinology: Conference report

Benefit/risk (B/R) assessment methods are increasingly being used by regulators and companies as an important decision-making tool and their outputs as the basis of communication. B/R appraisal of vaccines, as compared with drugs, is different due to their attributes and their use. For example, vaccines are typically given to healthy people, and, for some vaccines, benefits exist both at the population and individual level. For vaccines in particular, factors such as the benefit afforded through herd effects as a function of vaccine coverage and consequently impact the B/R ratio, should also be taken into consideration and parameterized in B/R assessment models. Currently, there is no single agreed methodology for vaccine B/R assessment that can fully capture all these aspects. The conference "Perspectives on Benefit-Risk Decision-making in Vaccinology," held in Annecy (France), addressed these issues and provided recommendations on how to advance the science and practice of B/R assessment of vaccines and vaccination programs.

CDC Online Course: Reproductive Health in Emergency Preparedness and Response

In an emergency, the needs of women of reproductive age, particularly pregnant and postpartum women, introduce unique challenges for public health and clinical care. Incorporating reproductive health issues and considerations into emergency preparedness and response is a relatively new field. In recent years, several resources and tools specific to reproductive health have been developed. However, there is still a need for training about the effects of emergencies on women of reproductive age. In an effort to train medical and public health professionals about these topics, the CDC Division of Reproductive Health developed Reproductive Health in Emergency Preparedness and Response, an online course that is available across the United States.

Influenza pathogenicity during pregnancy in women and animal models

Pregnant women are at the highest risk to develop severe and even fatal influenza. The high vulnerability of women against influenza A virus infections during pregnancy was repeatedly highlighted during influenza pandemics including the pandemic of this century. In 2009, mortality rates were particularly high among otherwise healthy pregnant women. However, our current understanding of the molecular mechanisms involved in severe disease development during pregnancy is still very limited. In this review, we summarize the knowledge on the clinical observations in influenza A virus-infected pregnant women. In addition, knowledge obtained from few existing experimental infections in pregnant animal models is discussed. Since clinical data do not provide in-depth information on the pathogenesis of severe influenza during pregnancy, adequate animal models are urgently required that mimic clinical findings. Studies in pregnant animal models will allow the dissection of involved molecular disease pathways that are key to improve patient management and care.

Dismantling the Taboo against Vaccines in Pregnancy

Vaccinating pregnant women in order to protect them, the fetus, and the child has become universal in no way at all. Prejudice in health professionals add to fears of women and their families. Both these feelings are not supported by even the smallest scientific data. Harmlessness for the mother and the child has been observed for seasonal, pandemic, or quadrivalent influenza, mono, combined polysaccharide or conjugated meningococcal or pneumococcal, tetanus toxoid, acellular pertussis, human papillomavirus, cholera, hepatitis A, Japanese encephalitis, rabies, anthrax, smallpox, yellow fever, mumps, measles and rubella combined, typhoid fever, inactivated or attenuated polio vaccines, and Bacillus Calmétte Guerin vaccines. Instead, the beneficial effects of influenza vaccine for the mother and the child as well as of pertussis vaccine for the child have been demonstrated. Obstetrician-gynecologists, general practitioners, and midwives must incorporate vaccination into their standard clinical care. Strong communication strategies effective at reducing parental vaccine hesitancy and approval of regulatory agencies for use of vaccines during pregnancy are needed. It must be clear that the lack of pre-licensure studies in pregnant women and, consequently, the lack of a statement about the use of the vaccine in pregnant women does not preclude its use in pregnancy.

Severe maternal morbidity due to respiratory disease and impact of 2009 H1N1 influenza A pandemic in Brazil: results from a national multicenter cross-sectional study

BACKGROUND

The aim of this study was to assess the burden of respiratory disease, considering the influenza A pandemic season (H1N1pdm09), within the Brazilian Network for Surveillance of Severe Maternal Morbidity, and factors associated with worse maternal outcome.

METHODS

A multicenter cross-sectional study, involving 27 referral maternity hospitals in five Brazilian regions. Cases were identified in a prospective surveillance by using the WHO standardized criteria for potentially life-threatening conditions (PLTC) and maternal near miss (MNM). Women with severe complications from respiratory disease identified as suspected or confirmed cases of H1N1 influenza or respiratory failure were compared to those with other causes of severe morbidity. A review of suspected H1N1 influenza cases classified women as non-tested, tested positive and tested negative, comparing their outcomes. Factors associated with severe maternal outcome (SMO = MNM + MD) were assessed in both groups, in comparison to PLTC, using PR and 95 % CI adjusted for design effect of cluster sampling.

RESULTS

Among 9555 cases of severe maternal morbidity, 485 (5 %) had respiratory disease. Respiratory disease occurred in one-quarter of MNM cases and two-thirds of MD. H1N1 virus was suspected in 206 cases with respiratory illness. Around 60 % of these women were tested, yielding 49 confirmed cases. Confirmed H1N1 influenza cases had worse adverse outcomes (MNM:MD ratio < 1 (0.9:1), compared to 12:1 in cases due to other causes), and a mortality index > 50 %, in comparison to 7.4 % in other causes of severe maternal morbidity. Delay in medical care was associated with SMO in all cases considered, with a two-fold increased risk among respiratory disease patients. Perinatal outcome was worse in cases complicated by respiratory disease, with increased prematurity, stillbirth, low birth weight and Apgar score < 7.

CONCLUSIONS

Respiratory disease, especially considering the influenza season, is a very severe cause of maternal near miss and death. Increased awareness about this condition, preventive vaccination during pregnancy, early diagnosis and treatment are required to improve maternal health.

The role of infection and sepsis in the Brazilian Network for Surveillance of Severe Maternal Morbidity

OBJECTIVE

To identify the burden of severe infection within the Brazilian Network for Surveillance of Severe Maternal Morbidity and factors associated with worse maternal outcomes.

METHODS

This was a multicentre cross-sectional study involving 27 referral maternity hospitals in Brazil. WHO's standardised criteria for potentially life-threatening conditions and maternal near miss were used to identify cases through prospective surveillance and the main cause of morbidity was identified as infection or other causes (hypertension, haemorrhage or clinical/surgical). Complications due to infection were compared to complications due to the remaining causes of morbidity. Factors associated with a severe maternal outcome were assessed for the cases of infection.

RESULTS

A total of 502 (5.3%) cases of maternal morbidity were associated with severe infection vs. 9053 cases (94.7%) with other causes. Considering increased severity of cases, infection was responsible for one-fourth of all maternal near miss (23.6%) and nearly half (46.4%) of maternal deaths, with a maternal near miss to maternal death ratio three times (2.8:1) that of cases without infection (7.8:1) and a high mortality index (26.3%). Within cases of infection, substandard care was present in over one half of the severe maternal outcome cases. Factors independently associated with worse maternal outcomes were HIV/AIDS, hysterectomy, prolonged hospitalisation, intensive care admission and delays in medical care.

CONCLUSIONS

Infection is an alarming cause of maternal morbidity and mortality and timely diagnosis and adequate management are key to improving outcomes during pregnancy. Delays should be addressed, risk factors identified, and specific protocols of surveillance and care developed for use during pregnancy.

Pregnancy-Related Mortality Resulting From Influenza in the United States During the 2009-2010 Pandemic

OBJECTIVE

To estimate the burden of pregnancy-related mortality resulting from influenza A (H1N1)pdm09 virus infection during the 2009-2010 pandemic influenza season.

METHODS

Data from the Centers for Disease Control and Prevention's Pregnancy Mortality Surveillance System were used to identify women whose death during or shortly after pregnancy was attributed or likely attributed to the influenza A (H1N1)pdm09 virus from April 15, 2009, through June 30, 2010. We report the characteristics of these women and enumerate cases resulting in death as the pandemic began, peaked, and resolved.

RESULTS

During the pandemic season, we identified 915 pregnancy-related deaths and 4,911,297 live births. Seventy-five (8.2%) women died as a result of confirmed influenza A (H1N1)pdm09 infection deaths and 34 (3.7%) women as a result of possible influenza A (H1N1)pdm09 infection deaths. The pregnancy-related mortality ratio for confirmed and possible (combined) influenza A (H1N1)pdm09 infection deaths was 2.2 per 100,000 live births. Most deaths occurred during the 2009 calendar year with the peak of the distribution of deaths over time occurring in October 2009.

CONCLUSION

Twelve percent of pregnancy-related deaths were attributed to confirmed or possible influenza A (H1N1)pdm09 infection during the 2009-2010 pandemic season. Because prediction of pandemics is difficult, planning for prevention of influenza and care for those women affected are critical for preventing associated severe maternal morbidity and mortality.

LEVEL OF EVIDENCE

III.

Respiratory Infections in the U.S. Military: Recent Experience and Control

This comprehensive review outlines the impact of military-relevant respiratory infections, with special attention to recruit training environments, influenza pandemics in 1918 to 1919 and 2009 to 2010, and peacetime operations and conflicts in the past 25 years. Outbreaks and epidemiologic investigations of viral and bacterial infections among high-risk groups are presented, including (i) experience by recruits at training centers, (ii) impact on advanced trainees in special settings, (iii) morbidity sustained by shipboard personnel at sea, and (iv) experience of deployed personnel. Utilizing a pathogen-by-pathogen approach, we examine (i) epidemiology, (ii) impact in terms of morbidity and operational readiness, (iii) clinical presentation and outbreak potential, (iv) diagnostic modalities, (v) treatment approaches, and (vi) vaccine and other control measures. We also outline military-specific initiatives in (i) surveillance, (ii) vaccine development and policy, (iii) novel influenza and coronavirus diagnostic test development and surveillance methods, (iv) influenza virus transmission and severity prediction modeling efforts, and (v) evaluation and implementation of nonvaccine, nonpharmacologic interventions.

Increasing uptake of influenza vaccine by pregnant women post H1N1 pandemic: a longitudinal study in Melbourne, Australia, 2010 to 2014

BACKGROUND

A Melbourne (Australia) university affiliated, tertiary obstetric hospital provides lay and professional education about influenza vaccine in pregnancy annually each March, early in the local influenza season. Responding to a 2011 survey of new mothers' opinions, the hospital made influenza vaccine freely available in antenatal clinics from 2012. We wished to determine influenza vaccination uptake during pregnancy with these strategies 5 years after 2009 H1N1.

METHODS

Face to face interviews based on US Center for Disease Control and Prevention Pregnancy Risk Assessment Monitoring System with new mothers in postnatal wards each July, 2010 to 2014. We calculated recalled influenza vaccine uptake each year and assessed trends with chi square tests, and logistic regression.

RESULTS

We recorded 1086 interviews. Influenza vaccination during pregnancy increased by 6% per year (95% confidence interval 4 to 8%): from 29.6% in 2010 to 51.3% in 2014 (p < 0.001). Lack of discussion from maternity caregivers was a persistent reason for non-vaccination, recalled by 1 in 2 non-vaccinated women. Survey respondents preferred face to face consultations with doctors and midwives, internet and text messaging as information sources about influenza vaccination. Survey responses indicate messages about vaccine safety in pregnancy and infant benefits are increasingly being heeded. However, there was progressively lower awareness of maternal benefits of influenza vaccination, especially for women with risk factors for severe disease.

CONCLUSIONS

We observed improving influenza vaccination during pregnancy. There is potential to integrate technology such as text message or internet with antenatal consultations to increase vaccination coverage further.

Postpandemic Influenza A/H1N1pdm09 is still Causing Severe Perinatal Complications

Although influenza A/H1N1pdm09 is not causing a pandemic anymore, we recently observed two critically ill pregnant women infected by this virus. We present these cases to illustrate the possible severe complications of an – at that moment – seasonal influenza in pregnancy. We discuss the epidemiological differences between the pandemic and post pandemic phase and try to explain the high virulence of influenza A/H1N1pdm09 -infections in pregnancy by discussing insights in immunology during pregnancy. We conclude that although influenza A/H1N1pdm09 is in the post pandemic phase, infection by this influenza virus still needs to be considered in pregnant women with progressive respiratory dysfunction.