The added value of serologic testing: A comparison of influenza incidence among pregnant persons based on molecular-based surveillance versus serologic testing

Kittikraisak W.; Tinoco Y.; Levine M.Z.; Mott J.A.; Kanjanapattanakul W.; Munayco C.; Rawangban B.; Hunt D.R.; Mohanty S.; Wesley M.; Soto G.; Florian R.; Gonzales O.; Cabrera S.; Llajaruna E.; Asavapiriyanont S.; Ellison D.W.; Malek P.; Azziz-Baumgartner E.; Dawood F.S. · International Journal of Infectious Diseases (2024) · DOI: 10.1016/j.ijid.2024.107264

Resumen

Background: We examined the added value of serologic testing for estimating influenza virus infection incidence based on illness surveillance with molecular testing versus periodic serologic testing. Methods: Pregnant persons unvaccinated against influenza at <28 weeks gestation were enrolled before the 2017 and 2018 influenza seasons in Peru and Thailand. Blood specimens were collected at enrollment and ≤14 days postpartum for testing by hemagglutination inhibition assay for antibodies against influenza reference viruses. Seroconversion was defined as a ≥4-fold rise in antibody titers from enrollment to postpartum with the second specimen's titer of ≥40. Throughout pregnancy, participants responded to twice weekly surveillance contacts asking about influenza vaccination and influenza-like symptoms (ILS). A mid-turbinate swab was collected with each ILS episode for influenza real-time reverse transcription polymerase chain reaction (rRT-PCR). Results: Of 1,466 participants without evidence of influenza vaccination during pregnancy, 296 (20.2%) had evidence of influenza virus infections. Fifteen (5.1%) were detected by rRT-PCR only, 250 (84.4%) by serologic testing only, and 31 (10.5%) by both methods. Conclusions: Influenza virus infections during pregnancy occurred in 20% of cohort participants; >80% were not detected by a broad illness case definition coupled with rRT-PCR.