Effectiveness of quadrivalent influenza vaccine in pregnant women and infants, 2018–2019

• Published in: Vaccine 2020-06, Vol.38 (29), p.4625-4631
• Main Authors: Maltezou, Helena C., Asimakopoulos, George, Stavrou, Sofoklis, Daskalakis, George, Koutroumanis, Pelopidas, Sindos, Michael, Theodora, Marianna, Katerelos, Panos, Kostis, Evangelos, Gavrili, Stavroula, Kossyvakis, Athanassios, Theodoridou, Maria, Mentis, Andreas, Drakakis, Petros, Loutradis, Dimitrios, Rodolakis, Alexandros
• Format: Article
• Language: English
• Subjects: Antibiotics; Confidence intervals; Effectiveness; Female; Fetuses; Fever; Guillain-Barre syndrome; Health care; Hospitals; Humans; Illnesses; Immunization; Infant; Infants; Influenza; Influenza vaccination; Influenza Vaccines; Influenza, Human - epidemiology; Influenza, Human - prevention & control; Laboratories; Medical personnel; Miscarriage; Mortality; Pandemics; Pneumonia; Pregnancy; Pregnancy Complications, Infectious - epidemiology; Pregnancy Complications, Infectious - prevention & control; Pregnant Women; Premature labor; Professional ethics; Quadrivalent; Regression analysis; Seasons; Statistical analysis; Vaccination; Vaccines; Womens health
• ISSN: 0264-410X; 1873-2518
• DOI: 10.1016/j.vaccine.2020.04.060

Influenza is associated with an increased risk for serious illness, hospitalization and/or death in pregnant women and young infants. We prospectively studied the effectiveness of a quadrivalent inactivated influenza vaccine (QIV) in pregnant women and their infants during the 2018–2019 influenza season. A QIV was offered to pregnant women cared in a maternity hospital in Athens. Women were contacted weekly by telephone during the influenza season and PCR test was offered to women or infants who developed influenza-like illness (ILI). We studied 423 pregnant women and 446 infants. Unvaccinated pregnant women had a 7.5% probability to develop laboratory-confirmed influenza compared to 2.1% among vaccinated women (Odds ratio: 3.6; confidence intervals: 1.14–11.34, p-value = 0.029). Infants whose mothers were not vaccinated had a 7.9% probability to develop laboratory-confirmed influenza compared to 2.8% among infants of vaccinated mothers (Odds ratio = 2.849, confidence intervals: 0.892–9.102, p-value = 0.053). Cox regression analyses showed that QIV vaccination was significantly associated with a decreased probability for laboratory-confirmed influenza, ILI, healthcare seeking and hospitalization among pregnant women and a decreased probability for laboratory-confirmed influenza, healthcare seeking and prescription of antibiotics among infants. The effectiveness of QIV against laboratory-confirmed influenza was 72% among pregnant women and 64.5% among infants during the 2018–2019 influenza season. Vaccination of pregnant women with the QIV was associated with a lower risk for laboratory-confirmed influenza for them and their infants during the influenza season. Our findings strongly support the World Health Organization recommendations for vaccinating pregnant women against influenza.