NSW and Vic show excellent evidence that vaccine effectiveness against onward transmission is high (>86%)!
1/
I fit the R_eff vs vaccination data for NSW and Vic to a linear relationship, to get two parameters, the R_eff at zero vax, and the vax effectiveness against onward transmission (VET). The result:
NSW: R_eff(0 vax) = 1.65; VET = 86.1%
Vic: R_eff(0 vax) = 2.27; VET = 86.4%
2/
Solid lines are the Doherty model, linearized:
Doherty uses a transmission matrix which effectively weights some ages more than others in relevance to transmission. I assume vax affects everyone equally. I take a weighted average of VET = 89.7% for AZ (86%) and Pfizer (93%).
3/
Best fits indicate VET is ~86% (close to Doherty 86-93%). NSW and Vic agree very well.
Vic tracks consistently higher than NSW. This is roughly consistent with the difference between Doherty "high" and "medium" PHSM.
4/
We don't know why there is a difference (intrinsic to Syd & Melb? Weather? Lockdown fatigue?)
5/
Conclusions:
1) NSW and Vic data both consistent with a high (86%) vaccine effectiveness against onward transmission in the simplest model.
2) Doherty Inst model was very well calibrated for NSW.
6/
Conclusions cont'd:
3) VIC shows consistently higher R_eff compared to NSW. Vic would be justified in taking a more cautious approach to re-opening. If high R_eff due to "fatigue" then may be OK. If intrinsic to Melb, more restrictions needed after opening.
7//7
Addendum:
VET here is the *overall* vax effectiveness against transmission! (Not "onward")
If vaccine has X eff against infection, Y eff against (onward) transmission if infected, then overall VET = 1-(1-X)(1-Y).
In the six stories on COVID-19 @Hayley_Gleeson has written this year for @abcnews, a total of 19 expert sources (scientists or medical practitioners) are quoted.
10 out of 19 are members of zero-covid advocacy groups @TheWHN, @RealOzSAGE, @IndependentSage, @JohnSnowProject.
These zero-covid advocacy groups are discussed in this peer-reviewed article, which estimates that fewer than 1% of scientists working on COVID-19 are members of such groups.
In simple terms, "high" or "low" means high/low compared to the average of the last 12 months!
***By design*** it is impossible to use the data to compare the size of waves that are >12 months apart, or to calculate absolute numbers of infections.
2/
That's fine for what wastewater surveillance is designed for: A tool to check short term trends (is covid prevalence increasing or decreasing?)
It's not a quantitative measure of infections, and wasn't meant to be.
I think annual boosters are probably quite effective against onward transmission, probably 50% (a combination of VE|infection and VE|symptomatic which affects onward transmission).
2/
So boosting all adults (80% of population) would have a population-wide effect on transmission of roughly ~40%. On top of that the boosters offer some additional protection against severe disease.
3/
Really good article about the body of work from @zalaly using electronic health records to study post-acute symptoms of covid in the US Veterans Health Administration.
Mirrors many of the criticisms I've made of these studies over the years.
"At best, the studies are detecting health problems...when people with poor baseline health experience a severe infection of any kind, said @anders_hviid. At worst, the findings simply reflect bias...picking up on symptoms that are not caused by Covid-19 at all."
2/
I agree. I said the same thing when I looked at @zalaly's study comparing outcomes post-hospitalization for covid-19 and influenza.
"Conservative estimates suggest that over 200 million SARS-CoV-2 infected individuals worldwide will develop persistent symptoms of COVID-19" (C. Yang and S.J. Tebutt)
Tracking down the origin of that number led me to an absolute gem of a figure...
Top-level result here is that covid is 1.35 times [95% CI, 1.10-1.66] more deadly than influenza in this cohort (VA patients hospitalized due to covid or influenza).
Around 44% of those hospitalized for influenza had been vaccinated this season. While that's lower than the average vaccination for this age cohort (most >65) of around 54% (quite possibly because the vaccine works!)
But...
2/
...it's a lot higher than the fraction of >65s vaccinated for covid in the past season (29%).
So, in a group that's almost twice as likely to have been vaccinated for influenza than covid, covid is 35% deadlier. Not exactly earth-shattering.