As the global availability of vaccines increases, and reaches areas disproportionately affected by arsenic and malnutrition, resolving questions about potential environmental and biologic barriers to maternal immunization has become increasingly urgent. It is not known whether arsenic, a known developmental toxicant, can alter maternal immune responses to vaccination and whether exposure to arsenic during pregnancy can impair the transfer of maternal vaccine-induced antibody to the newborn. Moreover, factors known to affect arsenic metabolism and toxicity outcomes, particularly micronutrients critical in one-carbon metabolism, have not been evaluated in studies of arsenic immunotoxicity and vaccine-induced protection in mothers and their newborns. The objective in this study is to investigate whether maternal arsenic exposure and one-carbon metabolism micronutrient deficiencies alter maternal and newborn measures of vaccine-induced protection, respiratory morbidity, and systemic immune function following influenza vaccination during pregnancy.
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Change in influenza hemagglutination-inhibition (HI) antibody titer
Timeframe: Comparing baseline to 28 days post vaccination, birth, and 3 months post-partum
Mean percent influenza virus antibody avidity
Timeframe: Measured at baseline, 28 days post vaccination, birth, and 3 months post-partum
Seroconversion rate
Timeframe: Defined as a post-vaccination HI titer of ≥40 given a pre-vaccination titer ≤10 or, alternatively, a ≥4-fold increase in HI titer between pre-vaccination and post-vaccination sera if the pre-vaccination titer was >10.
Change in geometric mean HI antibody titer (GMT)
Timeframe: Comparing baseline to 28 days post vaccination, birth, and 3 months post-partum
Geometric mean ratio of infant:mother HI titer
Timeframe: Birth and 3 months post-partum
Change in influenza virus neutralizing antibody titer
Timeframe: Comparing baseline to 28 days post vaccination, birth, and 3 months post-partum
Change in anti-influenza virus total immunoglobulin G (IgG) enzyme immunoassay
Timeframe: Comparing baseline to 28 days post vaccination, birth, and 3 months post-partum