A sub-analysis from the Oxford-led COV001 and COV002 trials with Vaxzevria induced strong immune responses following either a prolonged second dose interval of up to 45 weeks or following a third boosting dose.
The results, published by the University of Oxford on the pre-print server of The Lancet, demonstrated that antibody levels remain elevated from baseline for at least one year following a single dose.
“Demonstrating our vaccine generates a robust and durable immune response is important for providing confidence in longer term protection. We look forward to continuing to partner with the University of Oxford and recommending bodies around the world to further evaluate the impact of these data,” says Mene Pangalos, Executive Vice President, BioPharmaceuticals R&D, AstraZeneca.
“In addition, a third dose of Vaxzevria given at least 6 months after a second dose, boosted antibody levels six fold and maintained T cell response.”
An extended interval between the first and second dose of Vaxzevria of up to 45 weeks, resulted in up to an 18 fold increase in antibody response, measured 28 days after the second dose. With a 45 week dosing interval between the first and second dose, antibody titres were four times higher than with a 12 week interval, demonstrating that a longer dosing interval is not detrimental but can derive stronger immunity.
In addition, a third dose of Vaxzevria given at least 6 months after a second dose, boosted antibody levels six fold and maintained T cell response. A third dose also resulted in higher neutralising activity against the Alpha (B.1.1.7, ‘Kent’), Beta (B.1.351, ‘South African’) and Delta (B.1.617.2, ‘Indian’) variants.
Both the late second dose and the third dose of Vaxzevria were less reactogenic than the first dose.
The analysis included volunteers aged 18 to 55 years who were enrolled in COV001 and COV002 trials and had received either a single dose or two doses of COVID-19 Vaccine AstraZeneca.