Effectiveness of seasonal trivalent influenza vaccination against hospital-attended acute respiratory infections in pregnant women: A retrospective cohort study

doi:10.1016/j.vaccine.2016.05.032

Vaccine

Volume 34, Issue 32, 12 July 2016, Pages 3649-3656

https://doi.org/10.1016/j.vaccine.2016.05.032 Get rights and content

Highlights

•
Pregnant women are at higher risk of serious influenza infection than non-pregnant women.
•
Few population-based studies have evaluated the effectiveness of seasonal influenza vaccine in pregnant women.
•
This cohort study compared the health of 3,007 vaccinated and 31,694 unvaccinated pregnant women.
•
Antenatal vaccination was associated with significantly fewer hospitalisations for respiratory disease.
•
These results support the value of implementing antenatal influenza vaccination programs.

Abstract

Background

Pregnant women are at risk of serious influenza infection. Although previous studies indicate maternal influenza vaccination can prevent hospitalisation in young infants, there is limited evidence of the effect in mothers.

Methods

A cohort of 34,701 pregnant women delivering between 1 April 2012 and 31 December 2013 was created using birth records. Principal diagnosis codes from hospital emergency department (ED) and inpatient records were used to identify episodes of acute respiratory illness (ARI) during the 2012 and 2013 southern hemisphere influenza seasons. Cox regression models were used to calculate adjusted hazard ratios (aHRs) by maternal vaccination status, controlling for Indigenous status, socioeconomic level, medical conditions, and week of delivery.

Results

3,007 (8.7%) women received a seasonal influenza vaccine during pregnancy. Vaccinated women were less likely to visit an ED during pregnancy for an ARI (9.7 visits per 10,000 person-days vs. 35.5 visits per 10,000 person-days; aHR: 0.19, 95% CI: 0.05−0.68). Vaccinated women were also less likely to be hospitalised with an ARI compared to unvaccinated women (16.2 hospitalisations per 10,000 person-days vs. 34.0 hospitalisations per 10,000 person-days; aHR: 0.35, 95% CI: 0.13−0.97).

Conclusions

Influenza vaccination during pregnancy was associated with significantly fewer hospital attendances for ARI in pregnant women.

Section snippets

Background

Seasonal influenza causes serious morbidity and mortality during annual epidemics, leading to nearly five million cases of severe illness and 500,000 deaths every year worldwide [1]. Severe complications resulting in hospitalisation mainly occur in high-risk groups, including pregnant women [2], [3], [4], [5]. Pregnant women are three times as likely as non-pregnant women to be hospitalised as a result of influenza infection and are at twice the risk of influenza-associated mortality [6]. The

Setting

Western Australia has a resident population of 2.6 million people, with 71% of the population residing in the metropolitan area [19]. There are approximately 33,000 births each year in Western Australia [20]. In Australia, seasonal trivalent influenza vaccine is offered at no cost to pregnant women under the National Immunisation Program [21]. The seasonal influenza vaccination program typically begins 15 March each year and vaccination activity ends by August. More than 70% of antenatal

Results

A total of 40,027 midwives records for women in the Perth, metropolitan area were provided for analysis, which linked to 5,541 vaccination records, 277 inpatient hospital records, 393 emergency department presentation records, and 229 notification records for laboratory-confirmed influenza; 4,903 records were removed because the woman spent no time at risk during influenza season while pregnant, 413 records were removed due to missing covariate information, and 10 records were excluded because

Discussion

To our knowledge, this is the first, population-based cohort study demonstrating a protective effect of seasonal trivalent influenza vaccine in preventing hospital-attended respiratory illness in pregnant women. Serious infections during pregnancy which require hospital intervention have been linked to a two to three fold increase in the odds of intrauterine fetal demise, preterm birth, caesarean delivery and fetal distress [29], indicating prevention of hospitalisations through antenatal

Conclusions

Evidence from this cohort study suggests that antenatal influenza vaccination protects against a proportion of severe acute respiratory illnesses resulting in emergency department presentation or hospital admission during pregnancy. Influenza infection during pregnancy poses a significant burden to pregnant women and their unborn infants [3], [4], and a large portion of women are being denied the benefits of seasonal influenza vaccination. Fewer than 50% of pregnant women receive an influenza

Author Contributions

AR performed all data management and analysis and led the writing of the manuscript; NK, HM, SO, and PE each contributed to the study design, interpretation of data, and writing of the manuscript. GS contributed to the study design.

Funding

This work was supported by the Western Australia Department of Health. This project was conducted as part of an evaluation of a state vaccination program.

Conference presentations

The findings described in this manuscript have been presented in brief at the 11th Australian Influenza Symposium in October 2015 in Geelong, Australia, as well as the Incidence, Severity and Impact of Influenza 2016 meeting of the International Society for Influenza and Other Respiratory Virus Diseases in Paris, France in January 2016.

Acknowledgements

The authors would like to thank the Linkage and Client Services Teams at the Western Australian Data Linkage Branch, in particular Alexandra Godfrey and Mikhalina Dombrovskaya, as well as the Data Custodians Maureen Hutchinson (Midwives Notification System), Dr Robyn Gibbs (Western Australia Antenatal Influenza Vaccination Database), Dr Gary Dowse (Western Australian Notifiable Infectious Diseases Database), Vikki Mirosevich (Hospital Morbidity Data Collection), and Andrew Puljic (Emergency

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Influenza vaccination during pregnancy is highly recommended. We examined the association between maternal influenza vaccination and adverse birth outcomes.
This cross-sectional study used data from the Pregnancy Risk Assessment Monitoring System (PRAMS) during 2012–2017. The primary exposure was the receipt of influenza vaccination during pregnancy. Low birth weight (LBW), preterm birth (PTB), and small for gestational age (SGA) were the primary outcomes. We conducted multivariable logistic regression models to estimate the adjusted odds ratios (AOR) and 95% confidence intervals (CI). Covariates used to adjust confounding included maternal age, marital status, education, race and ethnicity, insurance status before pregnancy, and smoking status. For a subgroup in 2012–2015, we analyzed the association between influenza vaccination in each trimester and adverse birth outcomes.
During 2012–2017, compared with unvaccinated women, women vaccinated during pregnancy had a lower risk of LBW and PTB. During 2012–2015, maternal influenza vaccination in the 1st and 3rd trimesters was associated with a reduced risk of LBW and PTB, and vaccination in the 3rd trimester had a greater protective effect than in the 1st trimester. Influenza vaccination was not associated with SGA regardless of trimester.
Our findings suggest that influenza vaccination during pregnancy is a safe and effective way to protect newborns.
Knowledge, attitudes, and practices (KAP) towards seasonal influenza and influenza vaccine among pregnant women in Kyrgyzstan: A cross-sectional study
2023, Vaccine
Influenza is an acute respiratory disease of global importance due to its pandemic potential. Pregnant women are more susceptible to severe illness and adverse outcomes of influenza, and vaccination is the most effective preventive measure for mother and infant. The coverage rate of influenza immunization in Kyrgyzstan is below national targets, despite the World Health Organization’s (WHO) recommendation to prioritize pregnant women for vaccination.
This study sought to understand drivers and barriers to influenza vaccine uptake in pregnant women in Kyrgyzstan. A knowledge, attitudes, and practices (KAP) survey was administered from December 2018 to March 2019 to 1,193 pregnant women aged 18 and older attending public health institutions in Kyrgyzstan. Multivariate regression analysis was used to determine the association between variables and outcomes of interest. Nearly half (56.2 %) of the 1,193 participants expressed willingness to be vaccinated during their current pregnancy. Participants with only a high school education had a significantly greater intention for vaccination (95 % CI: 1.4–3.2, p < 0.005) in the multivariate analysis compared to participants with university degrees. Participants with underlying health conditions had a higher intention of being vaccinated (95 % CI: 1.2–1.9, p < 0.005). The main reason for vaccine refusal was the belief that influenza vaccines could have adverse effects on the fetus (28.4 %); belief that vaccines could harm their pregnancy (24.3 %); and concern about vaccine effectiveness (10.6 %). These findings are important as they can inform targeted strategies and policy updates to facilitate influenza vaccine implementation and improve uptake among pregnant women in Kyrgystan, and may support strengthening of national influenza vaccine programs in other countries in Central Asia.
Longitudinal, population-based cohort study of prenatal influenza vaccination and influenza infection in childhood
2022, Vaccine
Citation Excerpt :
Since maternal antibodies cross the placenta during pregnancy [4], prenatal administration of seasonal inactivated influenza vaccine (IIV) is recommended for pregnant women in many countries, including Australia, at any stage of pregnancy to protect both mothers and their newborns from influenza illness during their first few months of life [2,5]. Several studies have found that maternal influenza vaccination is effective in reducing the risk of laboratory-confirmed influenza (LCI) illness and acute respiratory infections (ARIs) in young infants [6,7]. A systematic review and meta-analysis of four randomized controlled trials and five observational studies reported a lower risk of LCI infection by 48% and lower risk of LCI-associated hospitalizations by 72% among children aged less than six months following maternal influenza vaccination [6].
Influenza vaccination is recommended to protect mothers and their infants from influenza infection. Few studies have evaluated the health impacts of in utero exposure to influenza vaccine among children more than six months of age.
We used probabilistically linked administrative health records to establish a mother–child cohort to evaluate the risk of influenza and acute respiratory infections associated with maternal influenza vaccination. Outcomes were laboratory-confirmed influenza (LCI) and hospitalization for influenza or acute respiratory infection (ARI). Adjusted hazard ratios (aHRs) accounted for child’s Aboriginal status and were weighted by the inverse-probability of treatment.
14,396 (11.5%) children were born to vaccinated mothers. Maternally vaccinated infants aged < 6 months had lower risk of LCI (aHR: 0.33; 95% CI: 0.13, 0.85), influenza-associated hospitalization (aHR: 0.39; 95% CI: 0.16, 0.94) and ARI-associated hospitalization (aHR: 0.85; 95% CI: 0.77, 0.94) compared to maternally unvaccinated infants. With the exception of an increased risk of LCI among children aged 6 months to < 2 years old following first trimester vaccination (aHR: 2.28; 95% CI: 1.41, 3.69), there were no other differences in the risk of LCI, influenza-associated hospitalization or ARI-associated hospitalization among children aged > 6 months.
Study results show that maternal influenza vaccination is effective in preventing influenza in the first six months and had no impact on respiratory infections after two years of age.
Comparison of influenza antibody titers among women who were vaccinated in the 2<sup>nd</sup> and the 3<sup>rd</sup> trimesters of pregnancy
2021, Vaccine
Citation Excerpt :
Pregnant women are at higher risk for severe illness and complications from influenza, particularly during the 2nd and the 3rd trimesters due to changes in the immune system, heart, and lungs during pregnancy [1–3]. Influenza vaccination offers significant protection against influenza in pregnant women and may reduce the severity of influenza illness when infection does occur [1,4,5]. Influenza vaccination during pregnancy may also benefit the infants of vaccinated mothers.
We compared cord blood antibody titers in unvaccinated pregnant women to those vaccinated with seasonal influenza vaccine during the 2^nd and the 3^rd trimesters.
Pregnant women had cord blood collected at delivery for hemagglutination inhibition assay against vaccine reference viruses: A/California/07/2009 (H1N1)pdm09, A/Switzerland/9715293/2013 (H3N2), and B/Phuket/3073/2013 (Yamagata lineage). Geometric mean titer (GMT) ratios were calculated comparing vaccinated versus unvaccinated pregnant women, and women vaccinated in the 2^nd and the 3^rd trimesters. Proportions of women achieving defined titers were compared using the χ² test.
Of 307 women, 190 (62%) were unvaccinated. Fifty and 67 were vaccinated during the 2^nd and the 3^rd trimesters, respectively. Median enrollment age was 29 years (interquartile range 24–34). Sixteen (5%) women had pre-existing conditions, but none were immunocompromised. GMT ratios comparing vaccinated and unvaccinated women were 5.90 (95% confidence interval [CI] 5.06–6.96) for influenza A/California, 5.39 (95% CI 4.18–6.08) for influenza A/Switzerland, and 5.05 (95% CI 4.43–5.85) for influenza B/Phuket. Similarly, the GMT ratios comparing the 3^rd and the 2^nd trimester vaccinated women were 2.90 (95% CI 2.54–3.39), 2.82 (95% CI 2.56–3.13), and 2.83 (95% CI 2.56–3.14), respectively. The proportions of women with defined titers for the three vaccine reference viruses did not differ between 2^nd and 3^rd trimester vaccinated women (titers ≥40: 68–92% versus 70–93%; ≥110: 32% versus 33–63%; and ≥330: 4–10% versus 3–21%).
Pregnant women vaccinated against influenza had more placental transfer of influenza antibodies to their infants than unvaccinated women. Placental transfer of antibodies was higher among those vaccinated in the 3^rd trimester than in the 2^nd trimester. There was no difference in the proportions of women achieving antibody titers corresponding to protection against influenza in children. Findings support the current World Health Organization’s recommendation that pregnant women may be vaccinated in either 2^nd or 3^rd trimester of pregnancy.
Safety and protective effects of maternal influenza vaccination on pregnancy and birth outcomes: A prospective cohort study
2020, EClinicalMedicine
Citation Excerpt :
In addition to reassuring safety of maternal influenza vaccination, our study found influenza vaccination during pregnancy reduced a pregnant woman's risk of pre-delivery hospitalisation with influenza like illness by around 39%. This protective effect was most pronounced for those women who delivered during periods of high influenza activity, consistent with previous studies [20, 21]. Across the three influenza seasons 2015–2018 in South Australia, influenza A (H3N2) was the dominant circulating virus followed by influenza B [17].
Our study aimed to assess the safety and protective effect of maternal influenza vaccination on pregnancy and birth outcomes.
The study population comprised 1253 healthy nulliparous pregnant women in South Australia between 2015 and 2018. Participants were followed prospectively, with vaccination status (confirmed by medical records), pregnancy, and birth outcome data collected by midwives. Adjusted relative risks (aRRs) and adjusted hazard ratios (aHRs) were estimated accounting for time-varying vaccine exposure and temporal nature of each outcome.
Maternal influenza vaccination (48%, 603 of 1253) reduced the risk for pre-delivery hospitalisation with influenza like illness (aHR 0•61; 95% CI 0•39, 0•97). Maternal influenza vaccination was not associated with spontaneous abortion (aHR 0•42, 95% CI 0•12, 1•45), chorioamnionitis (aRR 0•78, 95% CI, 0•32, 1•88), gestational hypertension (aHR 0•78, 95% CI 0•47, 1•29), pre-eclampsia (aHR 0.84, 95% CI 0•54, 1•27), gestational diabetes (aHR 1•16, 95% CI 0•82, 1•66) nor preterm birth (aHR 0•94, 95% CI 0•59, 1•49). No associations between antenatal influenza vaccination and congenital anomalies, admission to the neonatal care unit, low Apgar scores, and mechanical ventilation were observed. Results were not materially changed after adjustment for pertussis vaccination. We observed a protective effect of maternal influenza vaccination on low birth weight (aHR 0•46, 95% CI 0•23, 0•94) and a marginal protective effect on small for gestational age births (aHR 0•65, 95% CI 0•40, 1•04) during periods of high influenza activity.
These results support the safety of maternal influenza vaccination and suggest a protective effect in reducing the rates of low birthweight and small for gestational age births.
There was no funding for this study.
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Coronavirus disease 2019 (COVID-19) emerged in 2019 and rapidly became a global pandemic, infecting millions and killing hundreds of thousands. The disease altered the practices of hospitals, clinics, and patients. These changes have implications for advanced practice registered nurses (APRNs). APRNs must remain current on best practices for treatment and diagnosis of COVID-19 while being cognizant of changes to their scope of practice. As the pandemic continues, APRNs will remain on the front lines treating patients with COVID-19 while also caring for vulnerable populations within the community. To provide high-quality care, APRNs must use a multifaceted approach that heeds ongoing updates to evidence-based practice.

View all citing articles on Scopus

¹: Deceased.

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Effectiveness of seasonal trivalent influenza vaccination against hospital-attended acute respiratory infections in pregnant women: A retrospective cohort study

Highlights

Abstract

Background

Methods

Results

Conclusions

Section snippets

Background

Setting

Results

Discussion

Conclusions

Author Contributions

Funding

Conference presentations

Acknowledgements

Am J Obstet Gynecol

Am J Obstet Gyncol

Vaccine

Vaccine

Am J Obstet Gyncol

Am J Obstet Gynecol

J Reprod Immunol

J Reprod Immunol

Influenza (seasonal)

Impact of influenza on acute cardiopulmonary hospitalizations in pregnant women

Am J Epidemiol

Impact of influenza exposure on rates of hospital admissions and physician visits because of respiratory illness among pregnant women

CMAJ

Hospitalizations with respiratory illness among pregnant women during influenza season

Obstet Gyncecol

Severe 2009 H1N1 influenza in pregnant and postpartum women in California

N Engl J Med

Mortality associated with seasonal and pandemic influenza among pregnant and nonpregnant women of childbearing age in a high-HIV-prevalence setting - South Africa, 1999−2009

Clin Infect Dis

Risk of fetal death after pandemic influenza virus infection or vaccination

N Engl J Med

Meeting of the Strategic Advisory Group of Experts on immunization, April 2012–conclusions and recommendations

Wkly Epidemiol Rec

Effectiveness of seasonal influenza vaccination during pregnancy in preventing influenza infection in infants, England, 2013/14

Euro Surveill

Influenza vaccine given to pregnant women reduces hospitalization due to influenza in their infants

Clin Infect Dis

Maternal influenza vaccination and effect on influenza virus infection in young infants

Arch Pediatr Adolesc Med

Effectiveness of maternal influenza immunization in mothers and infants

N Engl J Med

Is routine influenza immunization warranted in early pregnancy?

Vaccine

A global perspective of maternal influenza immunization

Vaccine

Effectiveness of influenza vaccine during pregnancy in preventing hospitalizations and outpatient visits for respiratory illness in pregnant women and their infants

Am J Perinatol

1306.5 Western Australia at a Glance