
Premature Vaccine Launch Has Deadly Repercussions - nsgi
https://www.npr.org/sections/goatsandsoda/2019/05/03/719037789/botched-vaccine-launch-has-deadly-repercussions
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schoen
Dengue fever is a mosquito-borne tropical illness that is now endemic to most
tropical countries and (unlike malaria) has no chemical prophylaxis and
(unlike yellow fever) has had no effective vaccine.

This article describes how there is now a dengue vaccine, which seems like
great news, but there's a catch. Dengue has a very unusual feature where
getting it _twice_ is not only possible but is frequently much worse than
getting it the first time, in the specific case where the second strain is
different from the first strain. The second (or subsequent) infection with a
different strain can cause a much more severe illness which may be fatal.

[https://en.wikipedia.org/wiki/Dengue_fever#Predisposition](https://en.wikipedia.org/wiki/Dengue_fever#Predisposition)

[https://en.wikipedia.org/wiki/Dengue_fever#Severe_disease](https://en.wikipedia.org/wiki/Dengue_fever#Severe_disease)

"While each serotype can cause the full spectrum of disease, virus strain is a
risk factor."

According to the article, the new vaccine is effective at reducing the risk of
dengue infections, _but_ is also comparable to a prior infection in terms of
increasing the _harmfulness_ of subsequent infections! So if you get the
vaccine without ever having had dengue before, you're less likely to get
dengue but it's also more likely to be worse if you do, which is probably a
bad tradeoff for most people.

The article goes on to say that the FDA has now approved the new vaccine for
use (only) in areas where dengue is present and (only) when the patient has a
confirmed history of prior infection -- in which case the vaccine is believed
to reduce risk of subsequent infections without also increasing their
severity. But a prior trial period of the vaccine in the Philippines did not
have this restriction, which means that it's believed to have decreased
infection risk _while increasing infection severity_ in some children, some of
whom died when they later contracted dengue from mosquito bites. Parents'
awareness of this history also reduced their willingness to have their
children receive other vaccines that were known to be safe:

"As result, vaccine coverage for childhood diseases in the Philippines, such
as the measles, has dropped, WHO says. And the Philippines is now facing a
large measles outbreak, with more than 26,000 cases and more than 355 deaths
during 2019."

:-(

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lotophage
I found out about the Dengvaxia controversy after frequently reading about
measles outbreak stories that often mentioned people who were from or who had
visited the Philippines. As a soon to be parent, the consequences of this and
the antivaxx "movement" utterly terrify me.

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cameldrv
The side effects seem bad, but even for those who have never had the disease,
by my reading, their overall chance of hospitalization is lower. If that's
true, you have to blame the sensationalistic reporting for not mentioning that
overall the vaccine is a huge positive.

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schoen
It's tricky to figure out how to consider it a positive or a negative. It
sounds like you're much less likely to get dengue with the vaccine, but if you
do get it, you're much more likely to die from it.

Suppose you had the no vaccine case with 100000 infections, 10 deaths, while
the vaccine case is 1000 infections, 15 deaths. It's complicated to say how to
assess whether this is worth it (and that evaluation will be affected by
things like loss aversion).

