Astrazeneca Vaccine 3 or 12 week gap?
The chairman of the WHO’s advisory group, Dr Alejandro Cravioto, has said that a longer gap is “associated with greater vaccine efficacy“, and that “The two doses of Astrazeneca should ideally be given between 8 and 12 weeks apart, for best protection from the disease“.
Trials involving 17,177 participants in the UK, Brazil, and South Africa have produced the following results.
- A single standard dose of vaccine provided 76% protection overall against symptomatic covid-19 in the first 90 days after vaccination .
- The study found vaccine efficacy reached 82.4% after a second dose in those with a dosing interval of 12 weeks or more (95% confidence interval 62.7% to 91.7%).
- If the two doses were given less than six weeks apart the efficacy was only 54.9% (CI 32.7% to 69.7%).
The World Health Organisation has also recommended the Oxford/AstraZeneca vaccine for Covid-19 for all age groups, including the over-65s.
More details at www.bmj.com
For comparison to the Pfizer vaccine, where the results were:
- Pfizer vaccine efficacy between the first and second doses was 52% (95% credible interval 29.5% to 68.4%).
- Seven or more days after the second dose, vaccine efficacy then rose to 95% (90.3% to 97.6%).
More at www.bmj.com