[conspire] Trend lines (was: COVID-19 "breakthrough" infections)

[Rick Moen]

I wrote:

> o  Pfizer has 95% efficacy.
> o  Moderna has 94.1% efficacy.
> o  J&J Janssen has 66.3% efficacy.

The three members of my immediate family being in Clan Moderna, 
I'm liking our odds -- but of course the awkward bit is that the
pandemic is not over, and we vaccinated people are playing a blind game
of "chicken" with the asymptomatically infected:  This is where
things become trickier.  One of the things we've learned during this 
pandemic is that, for _this_ bug, asymptomatic person-to-person
transmission in the community is, and remains, the heart of the problem.

Datum:  Last Friday, June 11, as on most days, 55 Californians died of
COVID-19.  This is far from over, and infections will now start rising,
again.  Hospitalisations statewide are down from their October 2020 peak
-- but only by half.

As of Friday, 55.6% statewide of _eligible_ (age 12+ [1]) Californians have 
been fully vaccinated, and another 11% have gotten one dose.  Youngsters
0-12 comprise about 15% of the state population, so 0.85 * 0.556 = 47.3%
of all Californians are fully vaccinated (as of Friday).  Of
California's 58 counties, the six with the highest vaccination percentage
are all in the Bay Area, Marin leading with 75 of 12+ covered (thus,
0.85 * 0.75 = 63.8% [2] of all residents).

Marin Co.:         75% of 12+, 64% of all residents
San Francisco Co.: 70% of 12+, 60% of all residents
San Mateo Co.:     69% of 12+, 59% of all residents  <- we are here!
Santa Clara Co.:   69% of 12+, 59% of all residents  <- greetings, neighbours!
Alameda Co.:       66% of 12+, 56% of all residents
Contra Costa Co.:  66% of 12+, 56% of all residents
Napa Co.:          63% of 12+, 54% of all residents
Sonoma Co.:        61% of 12+, 52% of all residents
Santa Cruz Co:[3]  60% of 12+, 51% of all residents
Solano Co:         49% of 12+, 42% of all residents


Epidemiogists' best guess of the percentage of vaccination _or_ previous
infection resulting in immunity, required for herd immunity among a
population, where outbreaks no longer grow, is 70% to 85%.  My local
two counties' 59% _vaccination_ coverage gets us close, but not there yet.

On the other hand, San Mateo County Health Dept. estimates that
R-effective for the county, as of yesterday, was 0.72.[4]  Santa Clara 
County's is 0.75, and the state as a whole is 0.78.[5]  That's great
news.  But there's a catch.

As a reminder, R-effective (a variant of R-zero) is the average number
of persons an infected person will also infect.  A value below 1.0 will
prospectively result in _decreasing_ spread, an epidemic burning itself
out, within the area in question.  The $10,000 question is whether our
good R-effective will persist.  Data modeling says _no_.  R-effective
for San Mateo County is estimated to have risen in recent days to 1.12,
crossing the critical 1.0 level on June 6th.[6]

Bottom line:  Watch those trend lines.


Pfizer expects to get an FDA Emergency Use Authorization for ages 2-11 
around September, which will certainly make the autumn 2021 school term
safer.


[1] Also, some folks are ineligible for medical reasons, but few enough
to disregard in present calculations.

[2] For calculation simplicity, I'm assuming age skew is the same
statewide, 85% being age 12+.  For obvious reasons, California is
varied in this and other pandemic-relevant areas such as housing
density, income/mobility, etc.  E.g., rural Lassen County, with only 22%
of residents age 12+ vaccinated, has the benefit of very low density, but
suffers the risk of its paltry hospital capacity getting overwhelmed.

[3] Santa Cruz County is _not_ considered a Bay Area county, unlike the
other nine, but is a lot closer to me than the North Bay counties,
so I care more.

[4] https://www.smchealth.org/data-dashboard/county-data-dashboard

[5] https://calcat.covid19.ca.gov/cacovidmodels/?ftag=MSF0951a18

[6] https://calcat.covid19.ca.gov/cacovidmodels/?ftag=MSF0951a18 (still,
    but using the selector to pick our county specifically).  OTOH,
    Santa Clara County, a mile south of our house, is holding at
    R-effective of 0.75.  At this date, San Mateo County is one of two
    California "hot spots" of rising spread, the other being rural Modoc 
    County with R-effective = 1.36.