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Observational Study
. 2021 Jul;15(4):446-456.
doi: 10.1111/irv.12836. Epub 2021 Jan 16.

A Retrospective observational cohort study of the effect of antenatal influenza vaccination on birth outcomes in Cape Town, South Africa, 2015-2016

Meredith L McMorrow  1   2   3 , Liza Rossi  4 , Susan Meiring  5 , Katherine Bishop  4 , Raphaela Itzikowitz  6 , Washiefa Isaacs  4 , Faakhiera Stellenboom  4 , Sibongile Walaza  4   7 , Orienka Hellferscee  4   8 , Florette K Treurnicht  4 , Heather J Zar  6   9 , Stefano Tempia  1   2   4   10 , Cheryl Cohen  4   7
Affiliations
Observational Study

A Retrospective observational cohort study of the effect of antenatal influenza vaccination on birth outcomes in Cape Town, South Africa, 2015-2016

Meredith L McMorrow et al. Influenza Other Respir Viruses. 2021 Jul.

Abstract

Background: There are conflicting data concerning the impact of antenatal influenza vaccination on birth outcomes including low birthweight (LBW), preterm birth, small for gestational age (SGA), and stillbirth.

Methods: We conducted a retrospective observational cohort study of infants born to women residing in Mitchells Plain, Cape Town. Infants were born at 4 health facilities during May 28 - December 31, 2015 and April 15 - December 31, 2016. We performed crude and multivariable logistic regression, propensity score (PS) matching logistic regression, and inverse probability of treatment weighted (IPTW) regression to assess vaccine effectiveness (VE) against LBW, preterm birth, SGA, and stillbirth adjusting for measured confounders.

Results: Maternal vaccination status, antenatal history, and ≥1 birth outcome(s) were available for 4084/5333 (76.6%) pregnancies, 2109 (51.6%) vaccinated, and 1975 (48.4%) unvaccinated. The proportion LBW was lower in vaccinated (6.9%) vs. unvaccinated (12.5%) in multivariable [VE 0.27 (95% CI 0.07-0.42)], PS [VE 0.30 (95% CI 0.09-0.51)], and IPTW [VE 0.24 (95% CI 0.04-0.45)]. Preterm birth was less frequent in vaccinated (8.6%) than unvaccinated (16.4%) in multivariable [VE 0.26 (0.09-0.40)], PS [VE 0.25 (95% CI 0.09-0.41)], and IPTW [VE 0.34 (95% CI 0.18-0.51)]. The proportion SGA was lower in vaccinated (6.0%) than unvaccinated (8.8%) but not in adjusted models. There were few stillbirths in our study population, 30/4084 (0.7%).

Conclusions: Using multiple analytic approaches, we found that influenza vaccination was associated with lower prevalence of LBW (24-30%) and preterm birth (25-34%) in Cape Town during 2015-2016.

Keywords: influenza vaccines; pregnancy outcome; premature birth.

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Figures

FIGURE 1
FIGURE 1
Influenza activity and number of women vaccinated by week, Cape Town, South Africa, 2015‐2016
FIGURE 2
FIGURE 2
Summary of enrolled mothers who received antenatal influenza vaccination and those who did not receive antenatal influenza vaccination with data available on at least one birth outcome, Cape Town, South Africa, 2015‐2016
See this image and copyright information in PMC

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References

    1. Jamieson DJ, Honein MA, Rasmussen SA, et al. H1N1 2009 influenza virus infection during pregnancy in the USA. Lancet. 2009;374(9688):451–458. - PubMed
    1. Van Kerkhove MD, Vandemaele KA, Shinde V, et al. Risk factors for severe outcomes following 2009 influenza A (H1N1) infection: a global pooled analysis. PLoS Med. 2011;8(7):e1001053. - PMC - PubMed
    1. Tempia S, Walaza S, Cohen AL, et al. 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. 2015;61(7):1063–1070. - PMC - PubMed
    1. Poehling KA, Edwards KM, Weinberg GA, et al. The underrecognized burden of influenza in young children. N Engl J Med. 2006;355(1):31–40. - PubMed
    1. Cohen C, Walaza S, Treurnicht FK, et al. In‐ and Out‐of‐hospital Mortality Associated with Seasonal and Pandemic Influenza and Respiratory Syncytial Virus in South Africa, 2009–2013. Clin Infect Dis. 2018;66(1):95–103. - PMC - PubMed

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