The Pregnancy and Influenza Multinational Epidemiologic (PRIME) study: a prospective cohort study of the impact of influenza during pregnancy among women in middle-income countries

Abstract

BackgroundThe World Health Organization identifies pregnant women as at high-risk for severe influenza, but influenza vaccines are underutilized among pregnant women. Data on influenza burden during pregnancy are largely limited to high-income countries and data on the impact of influenza on birth and perinatal outcomes are scarce.Methods/designThis prospective, longitudinal cohort study of pregnant women in middle-income countries is designed to address three primary objectives: 1) to evaluate the effect of laboratory-confirmed influenza during pregnancy on pregnancy and perinatal outcomes; 2) to estimate the incidences of all-cause acute respiratory illness and laboratory-confirmed influenza during pregnancy; and 3) to examine the clinical spectrum of illness associated with influenza viruses. Through a multi-country network approach, three sites aim to enroll cohorts of 1500–3000 pregnant women just before local influenza seasons. Women aged ≥ 18 years with expected delivery dates ≥ 8 weeks after the start of the influenza season are eligible. Women are followed throughout pregnancy through twice weekly surveillance for influenza symptoms (≥ 1 of myalgia, cough, runny nose, sore throat, or difficulty breathing) and have mid-turbinate nasal swabs collected for influenza virus testing during illness episodes. Primary outcomes include relative risk of preterm birth and mean birth weight among term singleton infants of women with and without reverse transcription polymerase chain reaction-confirmed influenza during pregnancy. Gestational age is determined by ultrasound at < 28 weeks gestation and birth weight is measured by digital scales using standardized methods. Sites are primarily urban in Bangkok, Thailand; Lima, Peru; and Nagpur, India. All sites recruit from antenatal clinics at referral hospitals and conduct surveillance using telephone calls, messaging applications, or home visits. Nasal swabs are self-collected by participants in Thailand and by study staff in Peru and India. During the first year (2017), sites enrolled participants during March–May in Peru and May–July in India and Thailand; 4779 women were enrolled.DiscussionThis study aims to generate evidence of the impact of influenza during pregnancy to inform decisions by Ministries of Health, healthcare providers, and pregnant women in middle-income countries about the value of influenza vaccination during pregnancy.

What do pregnant women think about influenza disease and vaccination practices in selected countries

“…Pregnant women were eligible for study participation if they were ≥18 y old and with at least 8 weeks of pregnancy remaining before the end of the influenza season in their countries. 15 Following the same protocol, participants completed an interview at enrollment that collected data on sociodemographic characteristics and asked whether the participant had heard of influenza and influenza vaccine prior to study enrollment. 22 If the participant indicated they had heard of influenza prior to study enrollment, they were asked additional questions regarding knowledge, attitudes, and practices of influenza disease and vaccination (Supplementary material).…”

“…For participants who reported receiving influenza vaccine during the current pregnancy, vaccination status was verified using medical records such as vaccination cards or hospital vaccination records. 15 …”

“…Detailed study methods and site descriptions have been previously published. 15 Influenza vaccination policies for pregnant woman differed by study site (Table 1). In Thailand, a policy offering influenza vaccination free of charge to pregnant women in their second and third trimesters of gestation was implemented in 2009; however, vaccination coverage in this group was reported to be low (range 0.9% to 1.1%) during the first 3 y of policy implementation.…”

“…[7][8][9][10][11][12][13][14] Understanding predictors of vaccination against influenza among pregnant women in low-and uppermiddle-income countries is important and may inform strategies for improving vaccine uptake in this population. Using data from a multi-country prospective cohort study conducted in a low middle-income country (India) and two upper middlecountries (Peru and Thailand, Table 1), 15 we assessed what factors were associated with influenza vaccination among CONTACT Carmen S. Arriola wus3@cdc.gov Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA. This work was authored as part of the Contributor's official duties as an Employee of the United States Government and is therefore a work of the United States Government.…”

“… 7–14 Understanding predictors of vaccination against influenza among pregnant women in low- and upper-middle-income countries is important and may inform strategies for improving vaccine uptake in this population. Using data from a multi-country prospective cohort study conducted in a low middle-income country (India) and two upper middle-countries (Peru and Thailand, Table 1 ), 15 we assessed what factors were associated with influenza vaccination among pregnant women by evaluating knowledge, attitudes, and practices related to influenza and influenza vaccination.…”