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TEDxRiodelaPlata

Romina Libster: The power of herd immunity

ロミーナ・リブスター: 集団免疫の力

November 20, 2014

ワクチンはどのように病気を防ぐのでしょう―そしてワクチン接種には小さすぎる子どもたちの間では? 「集団免疫」というコンセプトは感染の輪を断ち切る為に必要なクリティカルマス(変化が起きるのに必要な数の)人口が摂取を受けるというものです。健康衛生研究者のロミーナ・リブスターはどのように集団免疫が彼女の故郷の町で死に至るH1N1ウイルスの大流行を未然に防いだかを紹介します。(スペイン語)

Romina Libster - Medical researcher
Dr. Romina Libster investigates influenza and other respiratory viruses, searching for ways to most effectively keep viruses from spreading. Full bio

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Double-click the English subtitles below to play the video.
小児科医になり最初に診た患者のうちの一人は
00:12
One of the first patients
I had to see as a pediatrician was Sol,
生後一ヶ月の美しい赤ん坊 ソルでした
00:17
a beautiful month-old baby
ソルは重度の呼吸器感染症で入院したのでした
00:19
who was admitted with signs
of a severe respiratory infection.
私はその時まで これほど早く患者が急変する様を
見たことがありませんでした
00:23
Until then, I had never seen
a patient worsen so fast.
2日間 彼女は呼吸器に繋がれ
00:28
In just two days
she was connected to a respirator
3日目に亡くなりました
00:31
and on the third day she died.
ソルは百日咳にかかっていたのです
00:34
Sol had whooping cough.
部屋で症例について話し合い
沈痛な気持ちを切り替えた後
00:37
After discussing the case in the room
and after a quite distressing catharsis,
チーフレジデントがこう言ったのを覚えています
00:42
I remember my chief resident said to me,
「深呼吸して 顔を洗って来なさい
00:44
"Okay, take a deep breath. Wash your face.
ここからが一番大変だよ
00:48
And now comes the hardest part:
ご両親に説明しに行かなければ」
00:50
We have to go talk to her parents."
その時 何千という疑問が湧きました
00:53
At that time, a thousand questions
came to mind,
「1ヶ月の赤ん坊があんな不運に
見舞われなけりゃいけないなんて?」や
00:57
from, "How could a one-month-old
baby be so unfortunate?"
「もっと何かできたんじゃないかしら?」
01:03
to, "Could we have done
something about it?"
ワクチンが出来る前
01:07
Before vaccines existed,
多くの感染症が毎年何百万という
人々の生命を奪いました
01:09
many infectious diseases
killed millions of people per year.
1918年のインフルエンザ大流行では
01:14
During the 1918 flu pandemic
5千万人が亡くなりました
01:18
50 million people died.
アルゼンチンの総人口よりも多い数です
01:21
That's greater than Argentina's
current population.
皆さんの中には1956年にアルゼンチンを
襲ったポリオ大流行を
01:24
Perhaps, the older ones among you
remember the polio epidemic
知っている方も
いらっしゃるのではないでしょうか
01:28
that occurred in Argentina in 1956.
当時 ポリオワクチンはまだ無く
01:32
At that time, there was no vaccine
available against polio.
皆 手立てが無く
我を忘れていました
01:35
People didn't know what to do.
They were going crazy.
生石灰を木々に塗りたくったり
01:37
They would go painting trees
with caustic lime.
樟脳の入った小袋を
01:40
They'd put little bags of camphor
それが何か役に立つとでも言うかのように
子供の下着に入れたりしました
01:41
in their children's underwear,
as if that could do something.
ポリオ大流行により
何千人もの人々が亡くなりました
01:45
During the polio epidemic,
thousands of people died.
そして 何千人もの人々に
神経系の重篤な障害が残りました
01:50
And thousands of people were left
with very significant neurological damage.
これは読んで知ったことですが
01:56
I know this because I read about it,
ワクチンのお陰で私たちの世代は
01:59
because thanks to vaccines,
my generation was lucky
これ程酷い疫病に悩まされずに済んだのです
02:02
to not live through an epidemic
as terrible as this.
ワクチンは公衆衛生における
20世紀最大の成功の一つです
02:05
Vaccines are one of the great successes
of the 20th century's public health.
安全な飲み水に次いで
02:11
After potable water,
抗生物質に比べても 最も死亡率の
02:13
they are the interventions
that have most reduced mortality,
低下に寄与した発明で
02:16
even more than antibiotics.
ワクチンは天然痘のような重篤な病気を
地上から駆逐し
02:19
Vaccines eradicated terrible diseases
such as smallpox from the planet
麻疹や百日咳、ポリオなどといった病気による
02:24
and succeeded in significantly
reducing mortality
死亡率を大きく減少させることに寄与しました
02:28
due to other diseases such as measles,
死亡率を大きく減少させることに寄与しました
02:30
whooping cough, polio and many more.
これら全ての病気はワクチンで
防げる病気だと考えられています
02:34
All these diseases are considered
vaccine-preventable diseases.
これはどういうことでしょう?
02:41
What does this mean?
つまり こうした病気は
予防できるはずなのですが
02:43
That they are potentially preventable,
予防する為には
しなくてはならないことがあります
02:46
but in order to be so,
something must be done.
ワクチンを受ける必要があるのです
02:49
You need to get vaccinated.
今日ここにいる皆さんのほとんどは
02:52
I imagine that most,
if not all of us here today,
一生のうちいつか ワクチンを受けるでしょう
02:55
received a vaccine
at some point in our life.
でもこの中で何人が
青年期を過ぎてどのワクチンや
03:00
Now, I'm not so sure that many of us know
追加免疫を受けるべきかを
知っているかとなると分かりません
03:04
which vaccines or boosters
we should receive after adolescence.
いったい誰を守る為にワクチンを打つのだろう
03:10
Have you ever wondered
who we are protecting
と思ったことは?
03:14
when we vaccinate?
これはどういう意味でしょう?
03:16
What do I mean by that?
自分を守る以外の効果があるのでしょうか?
03:18
Is there any other effect
beyond protecting ourselves?
ご説明しましょう
03:24
Let me show you something.
今 一度も麻疹などの疫病が流行ったことのない
03:27
Imagine for a moment
今 一度も麻疹などの疫病が流行ったことのない
03:30
that we are in a city
街にいるとしましょう
03:32
that has never had a case
of a particular disease,
街にいるとしましょう
03:35
such as the measles.
ここでは誰も病気に罹ったことがなく
03:37
This would mean that no one in the city
has ever had contact with the disease.
その為に誰も麻疹への耐性が無く
ワクチンを打った事もありません
03:42
No one has natural defenses against,
nor been vaccinated against measles.
ある日 麻疹患者が街を訪れます
03:47
If one day, a person sick with the measles
appears in this city
麻疹は抵抗に遭うこと無く
03:52
the disease won't find much resistance
瞬く間に人から人へと感染って行き
03:56
and will begin spreading
from person to person,
コミュニティ全体へと感染してしまいます
03:59
and in no time it will disseminate
throughout the community.
しばらくすると
04:03
After a certain time
人口の殆どが病気になってしまいます
04:05
a big part of the population will be ill.
ワクチンが無い場合にはこうなりますが
04:09
This happened when there were no vaccines.
逆の場合を考えてみましょう
04:14
Now, imagine the complete opposite case.
この街では
04:19
We are in a city
人口の90%以上が麻疹への抗体があり―
04:21
where more than 90 percent
of the population
つまり
04:24
has defenses against
the measles, which means
既に一度麻疹に罹り自然に抗体が出来ているか
04:26
that they either had the disease,
survived, and developed natural defenses;
麻疹ワクチンを打っているか
どちらかです
04:30
or that they had been
immunized against measles.
ある日
04:35
If one day,
麻疹患者が街を訪れます
04:36
a person sick with the measles
appears in this city,
麻疹はかなりの抵抗に遭い
04:41
the disease will find much more resistance
人から人へとそれが伝染することもありません
04:44
and won't be transmitted
that much from person to person.
感染は最小限度に留まり
04:48
The spread will probably remain contained
麻疹の大流行は起こりません
04:52
and a measles outbreak won't happen.
ここで注意をして頂きたいのが
04:56
I would like you
to pay attention to something.
ワクチンを受けた人々は
05:00
People who are vaccinated
自分自身だけを守るのではなく
05:03
are not only protecting themselves,
コミュニティで病気が
流行することを防ぐという点で
05:06
but by blocking the dissemination
of the disease
05:09
within the community,
間接的にワクチンを受けていない
コミュニティの住人たちも
05:11
they are indirectly protecting
the people in this community
守っているのです
05:16
who are not vaccinated.
ワクチンを受けることで
05:18
They create a kind of protective shield
病気との接触を防ぐシールドを張り
05:21
which prevents them from
coming in contact with the disease,
人々を守ります
05:24
so that these people are protected.
このようにして
05:28
This indirect protection
コミュニティでまだ
ワクチンを受けていない人々が
05:31
that the unvaccinated people
within a community receive
ワクチンを接種した人々に囲まれる
ことで生まれる間接的なシールドは
05:35
simply by being surrounded
by vaccinated people,
「集団免疫」と呼ばれています
05:39
is called herd immunity.
コミュニティの人々の多くは
05:44
Many people in the community
この集団免疫だけによって
05:47
depend almost exclusively
on this herd immunity
病気から守られています
05:50
to be protected against disease.
この図表で見る
ワクチンを受けていない人々の割合は実際のものです
05:54
The unvaccinated people you see
in infographics are not just hypothetical.
彼らは私たちの甥、姪、子どもたちなどの
05:59
Those people are our nieces
and nephews, our children,
ワクチンを接種するには若すぎる
子どもたちです
06:02
who may be too young
to receive their first shots.
また 私たちの親が、兄妹が
06:06
They are our parents, our siblings,
知り合いが
06:09
our acquaintances,
何か病気にかかっていたり
06:10
who may have a disease,
免疫を弱める薬を飲んでいて
未接種かも知れないのです
06:12
or take medication
that lowers their defenses.
特定のワクチンへアレルギーが
ある人達もいます
06:17
There are also people who are
allergic to a particular vaccine.
ワクチンを接種しても
06:23
They could even be among us,
期待した効果が生じていない人は
06:25
any of us who got vaccinated,
ここにもいるかもしれません
06:27
but the vaccine didn't produce
the expected effect,
全てのワクチンが100%
常に効力がある訳では無いのです
06:31
because not all vaccines
are always 100 percent effective.
このような人たちは集団免疫だけによって
病気から守られています
06:35
All these people depend
almost exclusively on herd immunity
06:40
to be protected against diseases.
集団免疫を有効にする為には
06:44
To achieve this effect of herd immunity,
人口の大多数がワクチン接種を
受ける必要があります
06:49
it is necessary that a large percentage
of the population be vaccinated.
この必要な接種率は
「閾値(いき値)」と呼ばれ
06:54
This percentage is called the threshold.
閾値は様々な変数に左右されします
06:57
The threshold depends on many variables:
ウイルスの性質だったり
07:01
It depends on the germ's characteristics,
ワクチンが生じさせる免疫反応だったり
07:03
and those of the immune response
that the vaccine generates.
そしてそれらは全て共通点があります
07:07
But they all have something in common.
もしコミュニティでのワクチン接種率が
07:10
If the percentage of the population
in a vaccinated community
閾値以下であれば
07:15
is below this threshold number,
病気が伝染しやすくなるので
07:18
the disease will begin
to spread more freely
コミュニティの中で大流行が
発生する可能性があります
07:22
and may generate an outbreak
of this disease within the community.
一旦収束しかけた病気ですら
再流行するかも知れません
07:27
Even diseases which were
at some point controlled may reappear.
これは理論上の空論ではなく
07:36
This is not just a theory.
実際に起った状況で
今でも見られる現象です
07:38
This has happened,
and is still happening.
1998年 イギリス人の研究者が
07:42
In 1998, a British researcher
published an article
著名な医学誌に論文を発表しました
07:47
in one of the most important
medical journals,
麻疹、おたふく風邪、風疹を予防する
07:50
saying that the MMR vaccine,
新三種混合ワクチンは
07:52
which is given for measles,
mumps and rubella,
自閉症の発症に関連している
というものです
07:55
was associated with autism.
この発表はすぐさま 反響を呼びました
07:57
This generated an immediate impact.
人々はワクチン接種を止め
子どもたちへの接種も止みました
08:00
People began to stop getting vaccinated,
and stopped vaccinating their children.
それでどうなったでしょう?
08:05
And what happened?
世界中でワクチン接種した人口は
08:07
The number of people vaccinated,
閾値以下に減少し
08:09
in many communities around the world,
fell below this threshold.
世界各国の都市で麻疹の大流行が起こりました
08:13
And there were outbreaks of measles
in many cities in the world --
アメリカ ヨーロッパ などでもです
08:17
in the U.S., in Europe.
多くの人びとが病気になり
08:19
Many people got sick.
麻疹により亡くなりました
08:21
People died of measles.
それから
08:25
What happened?
この論文について医学界で大きな議論が起こり
08:27
This article also generated a huge stir
within the medical community.
何十人もの研究者達が
その真偽を確認するための研究を始めました
08:31
Dozens of researchers began to assess
if this was actually true.
しかし誰も
08:36
Not only could no one find
新三種混合ワクチンと自閉症の間に
因果関係を見いだせなかっただけでなく
08:40
a causal association between MMR
and autism at the population level,
この論文には正しくない主張が
書かれていたことが分かりました
08:45
but it was also found that this article
had incorrect claims.
論文は意図的に操作されていたのです
08:50
Even more, it was fraudulent.
08:53
It was fraudulent.
医学誌はこの論文を2010年に
正式に撤回しています
08:56
In fact, the journal publicly retracted
the article in 2010.
ワクチン接種を避ける理由や口実の一つは
09:04
One of the main concerns and excuses
for not getting vaccinated
副作用です
09:08
are the adverse effects.
ワクチンは薬と同じく
副作用を起こす可能性があります
09:11
Vaccines, like other drugs,
can have potential adverse effects.
ほとんどは軽度で一時的なもので
09:17
Most are mild and temporary.
そうした副作用よりも
常に利点の方が大きいのです
09:20
But the benefits are always greater
than possible complications.
私たちは病気の時は早く治りたいものです
09:27
When we are ill,
we want to heal fast.
私たちはよく
09:32
Many of us who are here
感染症にかかると抗生物質を飲み
09:34
take antibiotics
when we have an infection,
高血圧になると降圧剤を飲みます
09:37
we take anti-hypertensives
when we have high blood pressure,
循環器系の為の薬を飲みます
09:41
we take cardiac medications.
病気から早く治りたいからです
09:43
Why? Because we are sick
and we want to heal fast.
そこに疑問はほとんどありませんね
09:46
And we don't question it much.
では何故 自分達が健康なうちに
09:48
Why is it so difficult
to think of preventing diseases,
適切なケアをして 病気から身を守る事が
難しく感じるのでしょう?
09:53
by taking care of ourselves
when we are healthy?
私たちは病気になったり目前に危機が迫ると
09:56
We take care of ourselves a lot
when affected by an illness,
必死に身体のケアをしますね
10:00
or in situations of imminent danger.
ここにいる私たちの殆どが
10:03
I imagine most of us here,
2009年にアルゼンチンそして世界中で起こった
10:06
remember the influenza-A pandemic
A型インフルエンザの大流行を
覚えているはずです
10:10
which broke out in 2009
in Argentina and worldwide.
最初の症例が明らかになった時
10:14
When the first cases
began to come to light,
アルゼンチンは冬になったばかりで
10:17
we, here in Argentina,
were entering the winter season.
私たちは何も知らず
10:21
We knew absolutely nothing.
全ては混乱していました
10:23
Everything was a mess.
人々は町中でマスクを付け
アルコール除菌ジェルを買いに薬局へ走り
10:25
People wore masks on the street,
ran into pharmacies to buy alcohol gel.
薬局ではワクチン接種の列が出来
10:30
People would line up
in pharmacies to get a vaccine,
ましてそれがこの新しいウイルスに対して
10:34
without even knowing
if it was the right vaccine
有効なワクチンかどうかも
分かっていないというのに―
10:36
that would protect them
against this new virus.
私たちは何も知りませんでした
10:39
We knew absolutely nothing.
当時 私は Infant Foundationの
奨学生としての研究に加え
10:41
At that time, in addition to doing
my fellowship at the Infant Foundation,
南米式前払い制医療会社で
小児専門の家庭医として働いていました
10:46
I worked as a home pediatrician
for a prepaid medicine company.
シフトが始まる朝8時
10:51
I remember that I started
my shift at 8 a.m.,
それまでに50人の予約が
入っていました
10:54
and by 8, I already had a list
of 50 scheduled visits.
そこはカオスでした
誰もどうすればいいか分かっていませんでした
10:58
It was chaos;
people didn't know what to do.
私が診療した患者たちの傾向をよく覚えています
11:02
I remember the types of patients
that I was examining.
患者たちは通常冬に診る患者たちよりも
少し年齢が上で
11:07
The patients were a little older than
what we were used to seeing in winter,
熱が長く続いていました
11:11
with longer fevers.
その事を当時の職場の指導医に報告すると
11:14
And I mentioned that
to my fellowship mentor,
彼は彼で同じような報告を同僚から聞いていて
11:17
and he, for his part, had heard
the same from a colleague,
妊婦の多くや若者達が
11:21
about the large number
of pregnant women
11:24
and young adults
病院のICUにケアの難しい臨床例として
11:25
being hospitalized in intensive care,
収容されているということでした
11:28
with hard-to-manage clinical profiles.
それで私たちは何が起こっているのかを
解明しようとしました
11:32
At that time, we set out to understand
what was happening.
月曜の朝一番に車で
11:39
First thing Monday morning,
we took the car
ブエノスアイレスの郊外にある
11:42
and went to a hospital
in Buenos Aires Province,
新型インフルエンザ患者の
受け入れ病院へ行きました
11:45
that served as a referral hospital
for cases of the new influenza virus.
そこに着くとそこは混み合っていて
11:50
We arrived at the hospital;
it was crowded.
医療スタッフはNASAのような
防護服を着ていました
11:53
All health staff were dressed
in NASA-like bio-safety suits.
私たちは全員ポケットにマスクを忍ばせ
11:57
We all had face masks in our pockets.
神経質な私は2時間
息を止めていました
11:59
I, being a hypochondriac,
didn't breathe for two hours.
それでも何が起こっているかは分かりました
12:02
But we could see what was happening.
直ぐに私たちは市内の6病院そして
12:05
Immediately, we started
reaching out to pediatricians
ブエノスアイレス郊外の病院の
小児科医たちに連絡をし始めました
12:09
from six hospitals in the city
and in Buenos Aires Province.
目的は この新しいウイルスが
12:13
Our main goal was to find out
子どもたちに
どのような症状をもたらすか
12:16
how this new virus behaved
in contact with our children,
出来る限り短期間で調べることでした
12:20
in the shortest time possible.
マラソンのような過酷な仕事でした
12:23
A marathon work.
3ヶ月以内に
12:26
In less than three months,
この新たなH1N1ウイルスが持つ性質を
12:28
we could see what effect
this new H1N1 virus had
251人の感染し入院している子どもたちで
確認することができました
12:34
on the 251 children
hospitalized by this virus.
最も症状が重く出る子どもたちは
12:41
We could see which children
got more seriously ill:
4歳以下で特に1歳以下の子どもたち
12:45
children under four, especially those
less than one year old;
特に神経系の病を患う子どもたち
12:48
patients with neurological diseases;
そして慢性的な呼吸器疾患の
ある子どもたちでした
12:51
and young children
with chronic pulmonary diseases.
これらの高リスクグループを
見分けることは重要でした
12:55
Identifying these at-risk groups
was important
彼らをインフルエンザワクチン接種の
12:59
to include them as priority groups
優先リストへ組み込む為です
13:02
in the recommendations
for getting the influenza vaccine,
この情報はアルゼンチンのみならず
13:05
not only here in Argentina,
感染大流行がまだ襲っていない
国々にも伝えられました
13:07
but also in other countries
which the pandemic not yet reached.
1年後
13:12
A year later,
H1N1ウイルスワクチンが出来て
13:14
when a vaccine against the pandemic
H1N1 virus became available,
私たちは状況を見守りました
13:19
we wanted to see what happened.
高リスクグループを守ることを唱った
13:22
After a huge vaccination campaign
大掛かりなワクチンキャペーンの後
13:25
aimed at protecting at-risk groups,
高リスクグループの人々の93%が
ワクチンの接種を受けた病院では
13:30
these hospitals, with 93 percent
of the at-risk groups vaccinated,
H1N1ウイルスに羅患した
13:36
had not hospitalized a single patient
患者の入院は1例もありませんでした
13:40
for the pandemic H1N1 virus.
(拍手)
13:43
(Applause)
2009年には251例だったものが
13:47
In 2009: 251.
2010年にはゼロになりました
13:53
In 2010: zero.
ワクチン接種は個人の
責任に基づく行為ですが
13:56
Vaccination is an act
of individual responsibility,
集団へ大きな影響を及ぼす力があります
14:01
but it has a huge collective impact.
私がワクチンを接種すると
自分だけでなく
14:06
If I get vaccinated,
not only am I protecting myself,
周囲の人々をも守ることが出来るのです
14:11
but I am also protecting others.
百日咳を患ったソルは
14:15
Sol had whooping cough.
まだとても小さく
14:19
Sol was very young,
百日咳のワクチンを
まだ受けていませんでした
14:21
and she hadn't yet received
her first vaccine against whooping cough.
まだこう考えるのです
14:26
I still wonder what would have happened
もしソルの周りにいた全員が
ワクチンを接種していたらどうだったかしらと
14:30
if everyone around Sol
had been vaccinated.
(拍手)
14:37
(Applause)
Translator:Eriko T.
Reviewer:Tamami Inoue

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Romina Libster - Medical researcher
Dr. Romina Libster investigates influenza and other respiratory viruses, searching for ways to most effectively keep viruses from spreading.

Why you should listen

Dr. Romina Libster is a staff scientist and assistant investigator at the National Scientific and Technical Research Council, in Buenos Aires, Argentina. She received her Doctor of Medicine, with High Honors from the University Of Buenos Aires School Of Medicine in 2004. She then completed her pediatric internship and residency at the “Pedro de Elizalde” Children’s Hospital in Buenos Aires, Argentina from 2004-2008. Upon completion of this training she began her Post-Doctoral Research Fellowship at the Fundación INFANT in Buenos Aires under the tutelage of a renowned investigator, Dr. Fernando P. Polack. Shortly after assuming her fellowship position, she began the Master in Clinical Effectiveness Program in Buenos Aires. She conducted a series of complex and innovative studies on respiratory viruses, with a special focus on influenza. Romina was invited by Dr. Kathryn M. Edwards to join the Vanderbilt Vaccine Research Program team at Vanderbilt University in 2009 where she is  leading a large clinical trial to determine the safety and immunogenicity of sequential rotavirus vaccine schedules. In 2013, Dr. Libster returned to her home country through a repatriation program from Fundación INFANT where she joined the faculty at the institution.

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