ABSTRACT
BACKGROUND: Most approved vaccines utilise a two-dose strategy. To enable larger groups of patients to receive the first dose, the UK government increased the gap between the two doses from three to twelve weeks. Here we report on the immunogenicity of the first dose, including effect of age and vitamin D status on these levels over an 8 week-period. METHODS: Blood samples were collected from healthcare workers (HCW) receiving their first BNT162b2 vaccine dose between January and February 2021. Antibody (Ab) production was measured, prior to and weekly for 4 weeks post immunization, and a final measurement was performed at 8 weeks. Serum vitamin D concentrations were also measured at baseline. FINDINGS: Immunization of 97 HCW induced an Ab response that peaked 3â¢2 weeks post immunization to decrease thereafter. Ab levels remained positive at 8 weeks. IgG peak concentration was negatively associated with age (ß=-0â¢440, p<0.001). Response to immunization was also significantly affected by vitamin D status (p=0â¢022), on average 29â¢3% greater peak value in individuals with 25(OH)D>50nmol/L. No other variable showed significant effect. INTERPRETATION: The first dose of BNT162b2 produced Ab levels that remained positive after 8 weeks. Peak was greater in younger subjects and 25(OH)D>50nmol/L was beneficial. Booster campaigns should take into consideration vitamin D status which is at its highest following a period of sunshine exposure or following oral supplementation (400-1000IU daily). FUNDING: Abbott Diagnostics Ltd supplied the kits used to quantify the anti-SARS -CoV-2 Spike IgG and technical support as well as provided financial support for sample collections.