Poster Presentation Asia-Pacific Vaccine and Immunotherapy Congress 2026

Effect of time-of-day vaccination on the antibody response to mRNA and protein COVID-19 vaccine in adults (#117)

Rachel Higgins 1 , Nadia Mazarakis 1 2 , Cong Sun 1 , Zheng Quan (Ryan) Toh 1 2 , Yan Yung Ng 1 , Leanne Quah 1 , Skyy Luu 1 , Kathryn Bright 1 , Cattram Nguyen 1 2 3 , John Hart 1 , Eleanor Frances Georgina Neal 1 2 , Lien Anh Ha Do 1 2 , Claire von Mollendorf 1 2 , Kim Mulholland 1 2 4 , Francesca Orsini 1 3 , Paul Licciardi 1 2
  1. Murdoch Children's Research Institute, Parkville, VIC, Australia
  2. Department of Paediatrics, The University of Melbourne, Melbourne, Australia
  3. Clinical Epidemiology of Biostatistics Unit, Population Health, Murdoch Children's Research Institute, Melbourne, VIC, Australia
  4. London School of Hygiene & Tropical Medicine, United Kingdom

Time-of-day vaccination has been suggested as a feasible method to boost COVID-19 vaccine immunogenicity particularly in high-risk groups. However, several studies report inconsistent findings. We explored if time-of-day vaccination influences antibody responses to a fourth dose of mRNA (Moderna bivalent vaccine; mRNA-1273.214/mRNA-1273.222) or protein (Novavax; NVX-CoV-2373) COVID-19 vaccine as part of a randomised controlled trial (RCT) in Melbourne, Australia. Furthermore, we assessed if time-of-day vaccination effects differed by vaccine type or sex. At day 28 post-vaccination, antibody responses to all SARS-CoV-2 variants tested were higher for morning compared to afternoon vaccination in the Moderna group. Males in the Moderna group responded with higher antibodies to all SARS-CoV-2 variants tested after morning vaccination while responses in females were unaffected by time-of-day vaccination. Time-of-day vaccination had no effect on the response to Novavax, regardless of sex. Larger randomised trials are needed to confirm these findings to optimise vaccine timing strategies.