Comment

Pandemic H1N1 infection in pregnant women in the USA

Background: Seasonal influenza can cause severe illness leading to intensive care unit (ICU) admission and death.

Objective: To define the clinical and epidemiological features of severe seasonal influenza infection and factors associated with mortality.

Study design: A retrospective review was conducted on all patients with laboratory-confirmed influenza infection who were either admitted into the ICU or died in the two largest tertiary hospitals in Singapore from 2011-2015.

Results: Of 520 patients included in our study, 423 (81.3%) had influenza A infection and the rest with influenza B. Of patients with influenza A infection, 70.0% (296/423) were subtyped, of whom 24.0% (71/296) had A/H1N1pdm2009 and 76.0% (225/296) had A/H3N2. The median age of patients was 72 years (IQR 61–82). Males constituted 53.1% (276/520). Median Charlson comorbidity index score was 1 (IQR 0–3). About 70% had physical or radiological evidence of pneumonia upon admission. In-hospital mortality was 58.1% (302/520). On multiple logistic regression analysis, factors positively associated with mortality were age ≥65 years (adjusted odds ratio, aOR = 3.64, 95%CI 2.21–5.99, p < 0.001), malignancy (aOR = 2.53, 95%CI 1.12–5.73; p = 0.026), and hypoalbuminemia (aOR = 2.16, 95%CI 1.26–3.73; p = 0.005), while antiviral therapy (aOR = 0.33, 95%CI 0.17-0.63; p < 0.001) and ventilation (aOR = 0.23, 95% CI 0.13-0.39; p < 0.001) were negatively associated.

Conclusions: Patients with severe seasonal influenza infection were characterized by advanced age, hypoalbuminemia and presence of pneumonia on admission. Age ≥65 years, malignancy, and hypoalbuminemia were associated with increased mortality, and antiviral therapy and ventilation with decreased mortality.

Pregnant women and their unborn children are at high risk from both pandemic and seasonal influenza.

To explore views about influenza vaccination during pregnancy, in a pandemic and immediate post-pandemic context, among mothers and other carers of young children.

In a mixed methods study, caregivers from 16 childcare centres in Sydney, Australia, were surveyed in November and December 2009, and interviews were conducted with caregivers from six childcare centres between June 2009 and May 2011.

Emerging themes from 41 interviews conducted with mothers included: ‘pregnancy as a protected state’, ‘risk negotiation’ and ‘centrality of healthcare worker interaction’. Of 972 surveys distributed, 431 were completed (a response rate of 44%). Respondents perceived pandemic influenza risks to be greater for pregnant women than for their unborn children. Only 2% (9/383) of women reported being vaccinated against swine flu during pregnancy and 45% (168/383) indicated intent to receive swine flu vaccination in a future pregnancy.

The low rates of maternal influenza vaccination revealed in this study contrast to recent gains in vaccine uptake. Vaccination decision-making in pregnancy can be complex and contextually driven for some women. Healthcare workers, including midwives, have a key role in addressing women’s concerns about maternal influenza vaccination in both pandemic and interpandemic periods.

Policy makers need to be cognisant of women’s concerns and develop resources for both pregnant women and healthcare workers as part of both future pandemic planning and seasonal vaccination efforts.

In Australia, influenza vaccination is recommended for all women who will be pregnant during the influenza season. Vaccine safety and effectiveness are key concerns and influencers of uptake for both vaccine providers and families. We assessed the safety of receiving an influenza vaccination during any trimester of pregnancy with respect to preterm births and infant birthweight.

We conducted a nested retrospective cohort study of ‘FluMum’ participants (2012–2014). Our primary exposure of interest was influenza vaccination during pregnancy. The primary outcomes of interest were infant birthweight and weeks’ gestation at birth for live singleton infants. Analyses included comparisons of these birth outcomes by vaccination status and trimester of pregnancy an influenza vaccine was given. We calculated means, proportions, and relative risks and performed multivariable logistic regression for potential confounding factors.

In the 7126 mother-infant pairs enrolled in this study, mean maternal age at infant birth was 31.7 years. Influenza vaccine uptake in pregnancy was 34%. Most mothers with a known date of vaccination received a vaccine in the second trimester (51%). Those mothers with a co-morbidity or risk factor were 13% more likely to have influenza vaccine during pregnancy compared to other mothers (RR 1.13, 95% CI 1.04–1.24, p = 0.007). Mean weeks’ gestation at birth was 38.7 for the vaccinated and 38.8 for the unvaccinated group (p = 0.051). Infants in the vaccinated group weighed 15 g less in birthweight compared to the unvaccinated infants (95% CI −12.8 to 42.2, p = 0.29).

Results arising from this large Australian cohort study are reassuring with respect to two critical safety outcomes; preterm births and low infant birthweights. Studies examining a broader range of birth outcomes following influenza vaccination during pregnancy are required, particularly now that maternal vaccination in pregnancy has expanded to include pertussis as well as influenza.

To assess H1N1 antibody titers between vaccinated and nonvaccinated maternal and cord blood sera after the 2009 pandemic.

Antibody titers were measured in maternal blood and cord sera from three groups of pregnant women in this prospective study. Group 1 comprised women who received a trivalent seasonal influenza vaccine before conception, Group 2 comprised women who received a single injection of monovalent H1N1 vaccine during pregnancy, and Group 3 comprised women who were nonvaccinated. A seropositive or seroprotective hemagglutination inhibition (HAI) assay was defined as titer ≥ 1:40.

In this study, 500 healthy women were enrolled, of which 44 women were in the trivalent seasonal influenza vaccine group, 41 women were in the monovalent vaccine group, and 415 women were in the nonvaccinated group. The seropositive HAI titers in the three groups of mothers were 48%, 78%, and 12%, respectively. The HAI titers in the vaccinated groups were significantly higher than those in the nonvaccinated group. The HAI titers of the cord blood samples of the three groups were comparable to their respective maternal samples.

Seroprotection after the 2009 HIN1 pandemic was generally low in pregnant women. Vaccination during pregnancy yielded best seropositivity, whereas receiving a trivalent seasonal influenza vaccine before conception can offer better seroprotection to mothers and newborns than no vaccination.

La vacunación integral en la embarazada contempla la inmunización antes, durante o después de la gestación, y pretende proteger a la madre y al recién nacido. Se deben ponderar, de forma individualizada, los riesgos de padecer determinadas enfermedades frente a los potenciales beneficios y riesgos de la vacunación. En el contexto de enfermedades emergentes como la tos ferina, la actualización de las recomendaciones es de especial relevancia.

En el presente trabajo se describen las principales estrategias de vacunación en la embarazada consensuadas por diversos organismos expertos en vacunas. Se revisan las vacunas indicadas durante el embarazo, y aquellas que se deberían considerar en el posparto inmediato o previamente a la gestación. Finalmente, se detallan las vacunas a valorar antes de realizar un viaje durante la gestación.

Comprehensive vaccination in pregnancy is related to immunization before, during or after gestation, and aims to protect the mother and the newborn. The risks to which every pregnant woman is exposed and the potential benefits of vaccination must be evaluated on an individual basis. In the context of emerging infectious diseases such as pertussis, the need to update traditional recommendations is particularly important.

This article describes the main vaccination strategies during pregnancy agreed by different expert institutions. The vaccines indicated during pregnancy, and those that should be considered in the immediate postpartum or prior to pregnancy are reviewed. Finally, the vaccines to be considered during pregnancy before international travel are discussed.

To determine the prevalence of preexisting antibodies against the pandemic 2009 Influenza A (H1N1) virus in pregnant women and to evaluate the seroprotection of the mothers and infants by a single injection of monovalent vaccine during the pandemic.

Seropositivity rate of H1N1 among the nonvaccinated were compared with the vaccinated women. A single dose of vaccine, either nonadjuvanted AdimFlu-S or MF59-adjuvanted vaccine, was injected to the voluntarily vaccinated group. Maternal and cord blood sera were collected to evaluate the antibody response of the H1N1 virus. Seropositivity was defined as a hemagglutination inhibition titer to H1N1 (A/Taiwan/126/09) ≥1:40.

A total of 210 healthy, singleton, pregnant women were enrolled between January 2010 and May 2010. Seropositivity (≥1:40) of maternal hemagglutination inhibition was significantly higher in the vaccinated group (78%) than the nonvaccinated group (9.5%); 41.6% (20/48) of seropositive titers were >1:80. In nine vaccinated cases resulting in negative serum titers (<1:40), the prevalence of negative titer in the women received AdimFlu-S (14.8%, 4/31) was lower (p = 0.025) than those received MF59-adjuvanted vaccine (50%, 5/10).

Subclinical infection against H1N1 was low in Taiwanese pregnant women in the pandemic 2009. Seropositivity >75% could be achieved in the paired maternal and cord serum samples by a single injection of monovalent H1N1 vaccine.