Public Health England released leaked study - it's a copy of a manuscript submitted to a preprint server. It's not a study of who was vaccinated, but of vaccination status of people seeking Covid tests for symptoms ...1/n khub.net/documents/1359… HT @michael_jshaw @TheGazmanRants
...This study is a test negative case control study - it's a study design that's been used in a variety of vaccines. (Here's an article about this type of controlled study: journals.lww.com/epidem/Abstrac…)...2/n
...It's data from tests for the general community (called Pillar 2: doesn't include eg hospital testing). Data was linked to the National Immunisation Register, on Feb 22. Vaccination began in the UK on Dec 8 (with BNT-Pfizer), followed soon by Oxford-AstraZeneca vaccine...3/n
...There were 44,590 people aged 70 or over who tested positive for Covid-19; 112,340 who tested negative. Vaccination program started in people 80+ who weren't living in care homes, so they adjusted analyses for age & where people lived ...4/n 
...Here are their main conclusions: efficacy for both vaccines was similar against symptomatic disease after a single dose, but there was less data on Oxford-AstraZeneca because it was introduced later: <250 people 28 days+; about 1,000 people 28 days+ for BNT-Pfizer ...5/n
...One effect of the shorter timeframe for the Oxford-AstraZeneca vaccine results is that the growth of immunity from this vaccine hadn't plateaued. But they conclude that their results correspond to the higher efficacy rate (>75%) with longer dose interval in the trials ...6/n
...Still too early to know what results will be when people get their second doses at longer interval for both vaccines. There was already a reduction in risk of hospitalization & death for people aged 80+ vaccinate with BNT-Pfizer within 21 days .../7
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