Coincidentally with the news of the plague epidemic
in the post immediately below, Quanta Magazine is leading off their current issue with the headline story.
From what I understand, the plague vaccine is not as effective as some other disease vaccines, for example polio, a focus of the
Bill and Melinda Gates Foundation, which Mr. Gates this week said should be
eradicated by the end of this year rather than the 2018 target the Foundation was using as recently as June.
Back to the plague, according to the Centers for Disease Control
the efficacy of the vaccine is in question because of the lack of follow-up studies, so treatment with hard core antibiotics such as Cipro or Levaquin is probably the best bet in plague affected areas. Oddly enough one of my MD's is one of the go-to guys for tropical and infectious diseases, ebola etc. but I couldn't reach him before posting this piece.
Anyhoo, on to the big brains at Quanta:
If you didn't get a flu shot, you are endangering more than just your
own health. Calculations of herd immunity against common diseases don't
make exceptions.
As the annual flu season approaches, medical professionals are again
encouraging people to get flu shots. Perhaps you are among those who
rationalize skipping the shot on the grounds that “I never get the flu”
or “if I get sick, I get sick” or “I’m healthy, so I’ll get over it.”
What you might not realize is that these vaccination campaigns for flu
and other diseases are about much more than your health. They’re about
achieving a collective resistance to disease that goes beyond individual
well-being — and that is governed by mathematical principles
unforgiving of unwise individual choices.
When talking about vaccination and disease control, health
authorities often invoke “herd immunity.” This term refers to the level
of immunity in a population that’s needed to prevent an outbreak from
happening. Low levels of herd immunity are often associated with
epidemics, such as the measles outbreak in 2014-2015
that was traced to exposures at Disneyland in California. A study
investigating cases from that outbreak demonstrated that measles
vaccination rates in the exposed population may have been as low as 50 percent. This number was far below the threshold needed for herd immunity to measles, and it put the population at risk of disease.
The necessary level of immunity in the population isn’t the same for
every disease. For measles, a very high level of immunity needs to be
maintained to prevent its transmission because the measles virus is
possibly the most contagious known organism. If people infected with
measles enter a population with no existing immunity to it, they will on
average each infect 12 to 18 others.
Each of those infections will in turn cause 12 to 18 more, and so on
until the number of individuals who are susceptible to the virus but
haven’t caught it yet is down to almost zero. The number of people
infected by each contagious individual is known as the “basic
reproduction number” of a particular microbe (abbreviated R0), and it varies widely among germs. The calculated R0 of the West African Ebola outbreak was found to be around 2 in a 2014 publication, similar to the R0 computed for the 1918 influenza pandemic based on historical data.
If the Ebola virus’s R0 sounds surprisingly low to you,
that’s probably because you have been misled by the often hysterical
reporting about the disease. The reality is that the virus is highly
infectious only in the late stages of the disease, when people are
extremely ill with it. The ones most likely to be infected by an Ebola
patient are caregivers, doctors, nurses and burial workers — because
they are the ones most likely to be present when the patients are
“hottest” and most likely to transmit the disease. The scenario of an
infectious Ebola patient boarding an aircraft and passing on the disease
to other passengers is extremely unlikely because an infectious patient
would be too sick to fly. In fact, we know of cases of travelers who
were incubating Ebola virus while flying, and they produced no secondary
cases during those flights.
Note that the R0 isn’t related to how severe an infection is, but to how efficiently it spreads. Ebola killed about 40 percent of those infected in West Africa, while the 1918 influenza epidemic had a case-fatality rate of about 2.5 percent.
In contrast, polio and smallpox historically spread to about 5 to 7
people each, which puts them in the same range as the modern-day HIV
virus and pertussis (the bacterium that causes whooping cough).
Determining the R0 of a particular microbe is a matter of
more than academic interest. If you know how many secondary cases to
expect from each infected person, you can figure out the level of herd
immunity needed in the population to keep the microbe from spreading.
This is calculated by taking the reciprocal of R0 and subtracting it from 1. For measles, with an R0
of 12 to 18, you need somewhere between 92 percent (1 – 1/12) and 95
percent (1 – 1/18) of the population to have effective immunity to keep
the virus from spreading. For flu, it’s much lower — only around 50
percent. And yet we rarely attain even that level of immunity with vaccination....
...
MUCH MORE
Related:
The Black Death: Ecological Invasion Resembles a Drunken Walk More so Than Waves
And as noted in early September:
...No word from Swiss Re on whether the new strain would be considered a
trigger for the first ever pandemic bonds launched all of 10 weeks ago:
28 June 2017, Zurich
World
Bank launches first-ever bonds to combat pandemic outbreaks – Swiss Re
Capital Markets joint structurer and sole book-runner for transaction