For all those still debating the scientists dosing recommendations. Here is the paper I posted on the previous thread with clear data as to why this decision has been taken. In short, with Pfizer having more people protected at 89% is better than fewer people protected at 91%. Think of it like choosing between EITHER your mum or dad having 91% protection or ONE of them 89%. What would you choose?
www.cas.mhra.gov.uk/ViewandAcknowledgment/ViewAttachment.aspx?Attachment_id=103741
Published efficacy between dose 1 and 2 of the Pfizer vaccine was 52.4% (95% CI 29.5-68.4%). Based on the timing of cases accrued in the phase 3 study, most the vaccine failures in the period between doses occurred shortly after vaccination, the period before any immune response is expected. Using data for those cases observed between day 15 and 21, efficacy against symptomatic COVID-19 was estimated at 89% (95% CI 52-97%), suggesting that short term protection from dose 1 is very high from day 14 after vaccination. Similar findings were seen with the Moderna mRNA vaccine out to 108 days after the first dose (see Annex A).
The level of protection gained from a single dose of the AstraZeneca vaccine was assessed in an exploratory analysis. Vaccine efficacy from 22 days post dose 1 was 73% (95% CI 48.79-85.76). High protection against hospitalisation was seen from 21 days after dose 1 until two weeks after the second dose, suggesting that a single dose of the AstraZeneca will provide high short-term protection against severe disease. Protective immunity from the first dose likely lasts for a duration of 12 weeks (unpublished data).
With most vaccines an extended interval between the prime and booster doses leads to a better immune response to the booster dose. There is evidence that a longer interval between the first and second doses promotes a stronger immune response with the AstraZeneca vaccine.
There is currently no strong evidence to expect that the immune response from the Pfizer-BioNTech vaccine would differ substantially from the AstraZeneca and Moderna vaccines.
The second dose is still important to provide longer lasting protection and is expected to be as or more effective when delivered at an interval of 12 weeks from the first dose.