Publications by authors named "Christine Posavad"

Background: Following maternal COVID-19 vaccination, the persistence of antibodies in sera and breast milk for mothers and infants is not well characterized. We sought to describe the persistence of antibodies through 2 months after delivery in maternal and infant serum and breast milk following maternal COVID-19 mRNA vaccination and to examine differences by receipt of booster dose during pregnancy or postpartum.

Methods: This is a prospective cohort study with enrollment from July 2021 to January 2022 at 9 US academic sites.

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  • - The study assessed the effectiveness of a COVID-19 Sanofi booster vaccine by measuring neutralizing antibody levels in COVAIL recipients as a predictor of COVID-19 risk.
  • - Higher levels of antibody titers were found to be associated with a lower risk of COVID-19, indicated by adjusted hazard ratios of 0.30 and 0.25 for different titer measurements.
  • - An increase of 10-fold in the weighted average titer substantially reduced the risk, suggesting that higher antibody levels can offer better protection against the virus.
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  • Maternal vaccination with mRNA COVID-19 vaccines can help protect infants from COVID-19 by passing antibodies through the placenta during pregnancy.
  • Infants born to mothers who received a booster shot had higher levels of protective antibodies and were 56% less likely to contract COVID-19 in their first 6 months compared to those whose mothers did not receive a booster.
  • The study suggests that higher antibody levels at delivery reduce infection risk significantly, emphasizing the importance of maternal vaccination until infants can be vaccinated themselves.
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  • Vaccine protection against SARS-CoV-2 diminishes over time, making updated boosters necessary, as assessed in a phase 2 clinical trial with various mRNA and protein-based vaccines targeting multiple variants.* -
  • The trial measured safe levels of immunity by evaluating pseudovirus neutralization and found that variant-containing vaccines performed better than wild-type ones against different strains.* -
  • Updated vaccines targeting variants like Beta or Omicron BA.1 show strong neutralizing antibody responses across various SARS-CoV-2 strains while still maintaining immunity to the original virus.*
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We compared the serologic responses of 1 dose versus 2 doses of a variant vaccine (Moderna mRNA-1273 Beta/Omicron BA.1 bivalent vaccine) in adults. A 2-dose boosting regimen with a variant vaccine did not increase the magnitude or the durability of the serological responses compared to a single variant vaccine boost.

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  • A multicenter study analyzed the immune responses to COVID-19 vaccinations in pregnant women, focusing on both primary doses and boosters from July 2021 to January 2022.
  • Results showed that booster vaccinations led to significantly higher antibody levels in mothers and their newborns, particularly against the Omicron BA.1 variant, compared to those who received only the primary 2-dose series.
  • Efficient transplacental antibody transfer was observed for all vaccination regimens, indicating robust immune responses in mothers and effective protection for infants.
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As part of a multicenter study evaluating homologous and heterologous COVID-19 booster vaccines, we assessed the magnitude, breadth, and short-term durability of binding and pseudovirus-neutralizing antibody (PsVNA) responses following a single booster dose of NVX-CoV2373 in adults primed with either Ad26.COV2.S, mRNA-1273, or BNT162b2 vaccines.

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In this brief report, we compare the magnitude and durability of the serologic response of one versus two doses (separated by 56 days) of a variant vaccine (Moderna mRNA-1273 Beta/Omicron BA.1 bivalent vaccine) in adults.

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Vaccine protection against COVID-19 wanes over time and has been impacted by the emergence of new variants with increasing escape of neutralization. The COVID-19 Variant Immunologic Landscape (COVAIL) randomized clinical trial (clinicaltrials.gov NCT05289037) compares the breadth, magnitude and durability of antibody responses induced by a second COVID-19 vaccine boost with mRNA (Moderna mRNA-1273 and Pfizer-BioNTech BNT162b2), or adjuvanted recombinant protein (Sanofi CoV2 preS DTM-AS03) monovalent or bivalent vaccine candidates targeting ancestral and variant SARS-CoV-2 spike antigens (Beta, Delta and Omicron BA.

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In a randomized clinical trial, we compare early neutralizing antibody responses after boosting with bivalent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) messenger RNA (mRNA) vaccines based on either BA.1 or BA.4/BA.

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In a randomized clinical trial, we compare early neutralizing antibody responses after boosting with bivalent SARS-CoV-2 mRNA vaccines based on either BA.1 or BA.4/BA.

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Article Synopsis
  • Multiple safe and effective COVID-19 vaccines have been developed globally, utilizing different technologies and strategies to enhance their efficacy.! -
  • Vaccines with specific "prefusion-stabilizing S mutations" trigger stronger antibody responses in humans, leading to better recognition and neutralization of the spike protein compared to those without these modifications.! -
  • The study findings suggest a need for improved designs in future S-engineered vaccines to ensure they remain effective against new variants of the virus.!
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Background: Protection from SARS-CoV-2 vaccines wanes over time and is compounded by emerging variants including Omicron subvariants. This study evaluated safety and immunogenicity of SARS-CoV-2 variant vaccines.

Methods: This phase 2 open-label, randomized trial enrolled healthy adults previously vaccinated with a SARS-CoV-2 primary series and a single boost.

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  • The Omicron variant of SARS-CoV-2 includes various sublineages such as BA.2, BA.2.12.1, BA.4, and BA.5, which are now more prevalent than the earlier BA.1 variant.
  • These sublineages have mutations that enhance binding to ACE2, reduce cell fusion capabilities, and significantly lower neutralizing antibody responses from previous infections or vaccines.
  • However, booster shots using the original Wuhan-Hu-1 spike sequence can significantly enhance neutralizing antibody levels, suggesting that while initial vaccinations may be less effective against Omicron, boosters can still provide strong protection against severe illness.
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The Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exhibits reduced susceptibility to vaccine-induced neutralizing antibodies, requiring a boost to generate protective immunity. We assess the magnitude and short-term durability of neutralizing antibodies after homologous and heterologous boosting with mRNA and Ad26.COV2.

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Importance: COVID-19 vaccination is recommended during pregnancy for the protection of the mother. Little is known about the immune response to booster vaccinations during pregnancy.

Objective: To measure immune responses to COVID-19 primary and booster mRNA vaccination during pregnancy and transplacental antibody transfer to the newborn.

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Background: Pregnant women were excluded from investigational trials of COVID-19 vaccines. Limited data are available to inform pregnant and postpartum women on their decisions to receive a COVID-19 vaccine.

Methods: The goal of this observational, prospective cohort study is to evaluate the immunogenicity and safety of various Emergency Use Authorization (EUA) or licensed COVID-19 vaccines administered to pregnant or lactating women and describe the transplacental antibody transfer and kinetics of antibodies in mothers and infants.

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Waning immunity after two SARS-CoV-2 mRNA vaccinations and the emergence of variants precipitated the need for a third dose of vaccine. We evaluated early safety and immunogenicity after a third mRNA vaccination in adults who received the mRNA-1273 primary series in the Phase 1 trial approximately 9 to 10 months earlier. The booster vaccine formulations included 100 mcg of mRNA-1273, 50 mcg of mRNA-1273.

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Antigen-specific T persist and protect against skin or female reproductive tract (FRT) HSV infection. As the pathogenesis of HSV differs between humans and model organisms, we focus on humans with well-characterized recurrent genital HSV-2 infection. Human CD8+ T persisting at sites of healed human HSV-2 lesions have an activated phenotype but it is unclear if T can be cultivated .

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Background: Although the three vaccines against coronavirus disease 2019 (Covid-19) that have received emergency use authorization in the United States are highly effective, breakthrough infections are occurring. Data are needed on the serial use of homologous boosters (same as the primary vaccine) and heterologous boosters (different from the primary vaccine) in fully vaccinated recipients.

Methods: In this phase 1-2, open-label clinical trial conducted at 10 sites in the United States, adults who had completed a Covid-19 vaccine regimen at least 12 weeks earlier and had no reported history of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection received a booster injection with one of three vaccines: mRNA-1273 (Moderna) at a dose of 100 μg, Ad26.

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Vaccine-induced neutralizing antibodies (nAbs) are key biomarkers considered to be associated with vaccine efficacy. In United States government-sponsored phase 3 efficacy trials of COVID-19 vaccines, nAbs are measured by two different validated pseudovirus-based SARS-CoV-2 neutralization assays, with each trial using one of the two assays. Here we describe and compare the nAb titers obtained in the two assays.

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Background: While Coronavirus disease 2019 (Covid-19) vaccines are highly effective, breakthrough infections are occurring. Booster vaccinations have recently received emergency use authorization (EUA) for certain populations but are restricted to homologous mRNA vaccines. We evaluated homologous and heterologous booster vaccination in persons who had received an EUA Covid-19 vaccine regimen.

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Vaccine-induced neutralizing antibodies (nAbs) are key biomarkers considered to be associated with vaccine efficacy. In United States Government-sponsored phase 3 efficacy trials of COVID-19 vaccines, nAbs are measured by two different validated pseudovirus-based SARS-CoV-2 neutralization assays, with each trial using one of the two assays. Here we describe and compare the nAb titers obtained in the two assays.

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