From contact tracing of 4.1k households where index vaxxed >21days and contact positive 2-14 days of index
4 Jan 4 - 28 Feb from 365k households w/ single index case and 1m+ contacts
1/
No statistical difference between Ox/AZ and Pfizer efficacy for onward transmission
No statistical difference in effect by age
Well controlled:
adjusted for age of index case and contact, sex, region, calendar week, index of multiple deprivation quintile, household type
2/
limitations:
Pillar 2 symptomatic case only so may miss asymptomatic cases (=overestimate efficacy).
Assumed contact symptom >2days of index was transmission but cd be co-primary (=underestimate),
and all 2-14 days are household transmission not independent (=underestimate)
3/
Fantasy commentary letter in Lancet (not a peer reviewed study)!
It's an unreasonable proposition for most countries like the UK to achieve elimination + constraints of reality negates claimed economic and liberty benefits if attempted...
Some seasonality expected for resp viruses, hard to say how much. England had unique circumstance Feb 7-13th.
- week long cold snap across country of similar magnitude
- no change in restrictions
- no increase in daily mobility
1/
Due to variables being reasonably controlled we can estimate how temperature may affect general transmission dynamics.
Note Seasonality: viruses transmit at ALL times of year but climate affects biology and behaviour which impacts on how much transmission occurs.
2/
Cases by specimen date in England showed a marked deceleration in the rate of decline the week after the cold period. From more than -5% per day to less than -2%.
(daily change adjusted for day of the week effect in testing)
Scotland where data from care home residents and 85+ were vaxxed 1st. Follow up time after 5 weeks means age will confound VE. With few absolute events adjustment for age becomes statistically underpowered (and doesn't capture full care home risk). Hence wide confidence interval
Also interesting to think about vax tech.
Oxford uses chimp adenovirus vector. Although engineered not to replicate, it's tough and can persist for weeks-months before cleared. Continuing to stimulate immune response by causing Sars-Cov2 spike protein production.
But Ab tires don't increase until 2nd dose for Pfizer, especially in the older age cohort who are the priority vaccine targets. How much protection are we giving them?👇
The 86% is a pooled estimate of all ages with younger population dominating.