2329. Incidences and Characteristics of Influenza Among Pregnant Women in Middle-Income Countries: Preliminary Results of the Pregnancy and Influenza Multinational Epidemiologic (PRIME) Study

Abstract Background The World Health Organization recommends influenza vaccination for pregnant women. However, few data exist on influenza incidence and clinical course among pregnant women in middle-income countries where influenza vaccine use during pregnancy is often limited. We conducted a prospective cohort study of pregnant women to estimate incidences of influenza in Lima, Peru; Bangkok, Thailand; and Nagpur, India. Methods Prior to and early in the 2017 and 2018 influenza seasons, we enrolled pregnant women aged > 18 years with expected delivery dates > 8 weeks after the start of the season. We contacted women twice weekly until end of pregnancy to identify illnesses with myalgia, cough, runny nose, sore throat, or difficulty breathing and collected nasal swabs from symptomatic women for influenza real-time reverse transcription polymerase chain reaction testing. Using 2017 cohort data, we calculated crude incidences per 10,000 pregnancy-months during influenza season by site and trimester and overall incidence weighted for population of women of childbearing age in each country. Results We enrolled 4774 women with a median age of 26 years (interquartile range [IQR] 23–31) and gestational age of 20 weeks (IQR 15–24); 15% received influenza vaccine. Local influenza seasons spanned 4.5–8 months. Overall, 143 participants (3%) had influenza (113 (79%) influenza A and 30 (21%) influenza B). Weighted influenza incidence was 88.7/10,000 pregnancy-months (95% CI 68.6–114.8), though incidences varied up to two-fold by site (Figure 1). Incidences did not differ by pregnancy trimester (Figure 2). Among the 143 influenza episodes, the median duration was 7 days (IQR 5–10), 30% involved fever or chills, 43% disrupted daily activities, 47% prompted medical attention, 4% were associated with hospitalization, and < 1% were treated with antiviral medications. Conclusion Overall, pregnant women had an average risk of influenza of 0.9% per month of pregnancy spent in the influenza season with almost half of illnesses disrupting daily activities and prompting medical attention. Influenza-associated hospitalization was infrequent. These findings provide valuable inputs to estimate illnesses averted by vaccine programs and evaluate their cost–benefit among pregnant women in middle-income countries. Disclosures All authors: No reported disclosures.