A 3-month interval between doses of the Oxford COVID-19 vaccine results in higher vaccine efficacy than a 6-week interval, with the first dose offering 76% protection in the 3 months between doses.
These results, from an exploratory analyses from a phase 3 randomised controlled trial published in The Lancet, suggest that the interval between doses can be safely extended to 3 months given the protection a single dose offers, which may allow countries to vaccinate a larger proportion of the population more rapidly.
The authors note that this regimen may be beneficial while vaccine supplies are initially limited. Study lead author Professor Andrew Pollard, University of Oxford, UK, says: "Vaccine supply is likely to be limited, at least in the short term, and so policy-makers must decide how best to deliver doses to achieve the greatest public health benefit. Where there is a limited supply, policies of initially vaccinating more people with a single dose may provide greater immediate population protection than vaccinating half the number of people with 2 doses. In the long term, a second dose should ensure long-lived immunity, and so we encourage everyone who has had their first vaccine to ensure they receive both doses."