AstraZeneca’s COVID-19 vaccine showed strong immunity following late second dose or third dose

June 30, 2021

A sub-analysis from the University of Oxford-led trials with Vaxzevria, the COVID-19 vaccine from AstraZeneca, induced strong immune responses following either a prolonged second dose interval of up to 45 weeks or following a third dose, according to a news release from AstraZeneca.

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.

An extended interval between the first and second dose of Vaxzevria (formerly AZD1222) 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 neutralizing activity against the Alpha (B.1.1.7, 'Kent'), Beta (B.1.351, 'South African') and Delta (B.1.617.2, 'Indian') variants.

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