The overall objective of the project is to determine the impact of pregnancy on the response to influenza immunization.
The study compares immune responses to influenza vaccination between a group of pregnant women and a group of non-pregnant controls women. Specifically, the study has three aims: 1. To compare the quality of antibodies induced by influenza immunization in pregnant and non-pregnant women; 2. To identify immune predictors of vaccine responses in pregnant women and compare them to the determinants of vaccine responses in non-pregnant women; 3. To identify immune predictors of the transfer of maternal antibodies to the newborn following influenza immunization during pregnancy;
Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
SINGLE
Enrollment
109
Alpharix-Tetra®, Vaxigrip Tetra® and Influvac Tetra® were used as influenza vaccines in the 2020-2021, 2021-2022, and 2022-2023 seasons respectively.
CHU Saint-Pierre
Brussels, Belgium
Haemagglutination Inhibition Assay titre
Haemagglutination Inhibition Assay (HAI) titres are used to measure responses to relevant influenza strains. The HAI method exploits the property of the influenza virus to haemagglutinate red blood cells. HAI titres are determined as the highest serum dilution inhibiting haemagglutination. An HAI titre of \>=40 is considered protective in adults. HAI titres will be measured in : * Pregnant women * Non-pregnant women
Time frame: 28 days post vaccination
Haemagglutination Inhibition Assay titre
Haemagglutination Inhibition Assay (HAI) titres are used to measure responses to relevant influenza strains. The HAI method exploits the property of the influenza virus to haemagglutinate red blood cells. HAI titres are determined as the highest serum dilution inhibiting haemagglutination. An HAI titre of \>=40 is considered protective in adults. HAI titres will be measured in : * Pregnant women * In umbilical cord blood
Time frame: At delivery
Haemagglutination inhibition assay titre
Haemagglutination Inhibition Assay (HAI) titres are used to measure responses to relevant influenza strains. The HAI method exploits the property of the influenza virus to haemagglutinate red blood cells. HAI titres are determined as the highest serum dilution inhibiting haemagglutination. An HAI titre of \>=40 is considered protective in adults. HAI titres will be measured in : * Pregnant women: at day of vaccination, day 7 post-vaccination, day 28 post-vaccination, at delivery, week 6 and 12 post-delivery * Non-pregnant women: at day of vaccination, day 7, day 28, and Month 6 post-vaccination
Time frame: up to 11 months after vaccination
Micro neutralization assay titre
Micro neutralization assay (MNA) titres are measured on serum samples with detectable HAI titres to determine cross reactivity to related virus strains. This method assesses the ability of serum antibodies to prevent virus from infecting a single layer of cells in a micro titre plate. MNA titres will be measured in : * Pregnant women: at day of vaccination, day 7 post-vaccination, day 28 post-vaccination, at delivery, week 6 and 12 post-delivery * Non-pregnant women: at day of vaccination, day 7, day 28, and Month 6 post-vaccination
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Time frame: up to 11 months after vaccination
Influenza virus specific IgG titre
IgG titres specific to influenza virus Hemagglutinin (HA) and Neuraminidase (NA) are measured using conventional Enzyme-linked immunosorbent assay (ELISA) methods. The Enzyme-Linked Lectin Assay (ELLA) is used for detection of NA-specific antibodies only, using reverse genetics viruses with irrelevant HA to ensure only NA antibodies are measured. ELLA is an ELISA variant but adapted to measure the concentration of antibody to NA, determining the amount of sialic acid cleaved from fetuin. IgG titres specific to Influenza Antigens will be assessed by ELISA and ELLA in: * Pregnant women: at day of vaccination, day 7 post-vaccination, day 28 post-vaccination, at delivery, week 6 and 12 post-delivery * Non-pregnant women: at day of vaccination, day 7, day 28, and Month 6 post-vaccination
Time frame: up to 11 month after vaccination
Influenza virus specific IgG antibody avidity
IgG avidity will be measured using chaotropic salts. IgG avidity will be assessed in : * Pregnant women: at day of vaccination, day 7 post-vaccination, day 28 post-vaccination, at delivery, week 6 and 12 post-delivery * Non-pregnant women: at day of vaccination, day 7, day 28, and Month 6 post-vaccination
Time frame: up to 11 months after vaccination