Single-dose administration and the influence of the timing of the booster dose on immunogenicity and efficacy of ChAdOx1 nCoV-19 (AZD1222) vaccine: a pooled analysis of four randomised trials
Results of this analysis are consistent with those seen in trials and confirm that vaccine is efficacious (66.7% efficacy > 14 days after second dose), with results varying by dose interval in exploratory analyses (efficacy 76% from day 22 to 90 after vaccination).
Source:
The Lancet
SPS commentary:
In participants who received two standard doses, after the second dose, efficacy was higher in those with a longer prime-boost interval (vaccine efficacy 81.3% [95% CI 60·3–91·2] at ≥12 weeks) than in those with a short interval (vaccine efficacy 55.1% [33·0–69·9] at <6 weeks).
Based on these findings, researchers suggest “a 3-month dose interval might have advantages over a programme with a short dose interval for roll-out of a pandemic vaccine to protect the largest number of individuals in the population as early as possible when supplies are scarce, while also improving protection after receiving a second dose.”