Romina Libster: The power of herd immunity (with English subtitles) | TED

56,898 views ・ 2015-02-25

TED


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Translator: Gisela Giardino Reviewer: Romina Pol
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One of the first patients I had to see as a pediatrician was Sol,
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a beautiful month-old baby
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who was admitted with signs of a severe respiratory infection.
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Until then, I had never seen a patient worsen so fast.
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In just two days she was connected to a respirator
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and on the third day she died.
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Sol had whooping cough.
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After discussing the case in the room and after a quite distressing catharsis,
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I remember my chief resident said to me,
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"Okay, take a deep breath. Wash your face.
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And now comes the hardest part:
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We have to go talk to her parents."
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At that time, a thousand questions came to mind,
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from, "How could a one-month-old baby be so unfortunate?"
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to, "Could we have done something about it?"
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Before vaccines existed,
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many infectious diseases killed millions of people per year.
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During the 1918 flu pandemic
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50 million people died.
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That's greater than Argentina's current population.
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Perhaps, the older ones among you remember the polio epidemic
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that occurred in Argentina in 1956.
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At that time, there was no vaccine available against polio.
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People didn't know what to do. They were going crazy.
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They would go painting trees with caustic lime.
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They'd put little bags of camphor
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in their children's underwear, as if that could do something.
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During the polio epidemic, thousands of people died.
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And thousands of people were left with very significant neurological damage.
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I know this because I read about it,
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because thanks to vaccines, my generation was lucky
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to not live through an epidemic as terrible as this.
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Vaccines are one of the great successes of the 20th century's public health.
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After potable water,
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they are the interventions that have most reduced mortality,
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even more than antibiotics.
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Vaccines eradicated terrible diseases such as smallpox from the planet
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and succeeded in significantly reducing mortality
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due to other diseases such as measles,
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whooping cough, polio and many more.
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All these diseases are considered vaccine-preventable diseases.
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What does this mean?
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That they are potentially preventable,
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but in order to be so, something must be done.
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You need to get vaccinated.
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I imagine that most, if not all of us here today,
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received a vaccine at some point in our life.
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Now, I'm not so sure that many of us know
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which vaccines or boosters we should receive after adolescence.
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Have you ever wondered who we are protecting
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when we vaccinate?
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What do I mean by that?
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Is there any other effect beyond protecting ourselves?
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Let me show you something.
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Imagine for a moment
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that we are in a city
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that has never had a case of a particular disease,
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such as the measles.
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This would mean that no one in the city has ever had contact with the disease.
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No one has natural defenses against, nor been vaccinated against measles.
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If one day, a person sick with the measles appears in this city
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the disease won't find much resistance
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and will begin spreading from person to person,
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and in no time it will disseminate throughout the community.
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After a certain time
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a big part of the population will be ill.
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This happened when there were no vaccines.
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Now, imagine the complete opposite case.
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We are in a city
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where more than 90 percent of the population
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has defenses against the measles, which means
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that they either had the disease, survived, and developed natural defenses;
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or that they had been immunized against measles.
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If one day,
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a person sick with the measles appears in this city,
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the disease will find much more resistance
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and won't be transmitted that much from person to person.
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The spread will probably remain contained
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and a measles outbreak won't happen.
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I would like you to pay attention to something.
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People who are vaccinated
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are not only protecting themselves,
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but by blocking the dissemination of the disease
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within the community,
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they are indirectly protecting the people in this community
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who are not vaccinated.
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They create a kind of protective shield
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which prevents them from coming in contact with the disease,
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so that these people are protected.
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This indirect protection
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that the unvaccinated people within a community receive
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simply by being surrounded by vaccinated people,
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is called herd immunity.
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Many people in the community
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depend almost exclusively on this herd immunity
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to be protected against disease.
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The unvaccinated people you see in infographics are not just hypothetical.
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Those people are our nieces and nephews, our children,
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who may be too young to receive their first shots.
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They are our parents, our siblings,
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our acquaintances,
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who may have a disease,
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or take medication that lowers their defenses.
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There are also people who are allergic to a particular vaccine.
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They could even be among us,
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any of us who got vaccinated,
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but the vaccine didn't produce the expected effect,
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because not all vaccines are always 100 percent effective.
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All these people depend almost exclusively on herd immunity
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to be protected against diseases.
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To achieve this effect of herd immunity,
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it is necessary that a large percentage of the population be vaccinated.
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This percentage is called the threshold.
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The threshold depends on many variables:
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It depends on the germ's characteristics,
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and those of the immune response that the vaccine generates.
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But they all have something in common.
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If the percentage of the population in a vaccinated community
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is below this threshold number,
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the disease will begin to spread more freely
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and may generate an outbreak of this disease within the community.
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Even diseases which were at some point controlled may reappear.
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This is not just a theory.
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This has happened, and is still happening.
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In 1998, a British researcher published an article
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in one of the most important medical journals,
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saying that the MMR vaccine,
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which is given for measles, mumps and rubella,
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was associated with autism.
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This generated an immediate impact.
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People began to stop getting vaccinated, and stopped vaccinating their children.
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And what happened?
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The number of people vaccinated,
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in many communities around the world, fell below this threshold.
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And there were outbreaks of measles in many cities in the world --
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in the U.S., in Europe.
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Many people got sick.
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People died of measles.
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What happened?
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This article also generated a huge stir within the medical community.
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Dozens of researchers began to assess if this was actually true.
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Not only could no one find
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a causal association between MMR and autism at the population level,
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but it was also found that this article had incorrect claims.
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Even more, it was fraudulent.
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It was fraudulent.
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In fact, the journal publicly retracted the article in 2010.
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One of the main concerns and excuses for not getting vaccinated
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are the adverse effects.
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Vaccines, like other drugs, can have potential adverse effects.
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Most are mild and temporary.
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But the benefits are always greater than possible complications.
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When we are ill, we want to heal fast.
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Many of us who are here
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take antibiotics when we have an infection,
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we take anti-hypertensives when we have high blood pressure,
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we take cardiac medications.
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Why? Because we are sick and we want to heal fast.
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And we don't question it much.
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Why is it so difficult to think of preventing diseases,
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by taking care of ourselves when we are healthy?
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We take care of ourselves a lot when affected by an illness,
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or in situations of imminent danger.
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I imagine most of us here,
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remember the influenza-A pandemic
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which broke out in 2009 in Argentina and worldwide.
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When the first cases began to come to light,
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we, here in Argentina, were entering the winter season.
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We knew absolutely nothing.
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Everything was a mess.
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People wore masks on the street, ran into pharmacies to buy alcohol gel.
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People would line up in pharmacies to get a vaccine,
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without even knowing if it was the right vaccine
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that would protect them against this new virus.
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We knew absolutely nothing.
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At that time, in addition to doing my fellowship at the Infant Foundation,
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I worked as a home pediatrician for a prepaid medicine company.
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I remember that I started my shift at 8 a.m.,
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and by 8, I already had a list of 50 scheduled visits.
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It was chaos; people didn't know what to do.
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I remember the types of patients that I was examining.
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The patients were a little older than what we were used to seeing in winter,
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with longer fevers.
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And I mentioned that to my fellowship mentor,
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and he, for his part, had heard the same from a colleague,
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about the large number of pregnant women
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and young adults
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being hospitalized in intensive care,
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with hard-to-manage clinical profiles.
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At that time, we set out to understand what was happening.
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First thing Monday morning, we took the car
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and went to a hospital in Buenos Aires Province,
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that served as a referral hospital for cases of the new influenza virus.
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We arrived at the hospital; it was crowded.
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All health staff were dressed in NASA-like bio-safety suits.
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We all had face masks in our pockets.
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I, being a hypochondriac, didn't breathe for two hours.
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But we could see what was happening.
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Immediately, we started reaching out to pediatricians
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from six hospitals in the city and in Buenos Aires Province.
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Our main goal was to find out
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how this new virus behaved in contact with our children,
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in the shortest time possible.
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A marathon work.
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In less than three months,
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we could see what effect this new H1N1 virus had
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on the 251 children hospitalized by this virus.
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We could see which children got more seriously ill:
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children under four, especially those less than one year old;
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patients with neurological diseases;
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and young children with chronic pulmonary diseases.
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Identifying these at-risk groups was important
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to include them as priority groups
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in the recommendations for getting the influenza vaccine,
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not only here in Argentina,
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but also in other countries which the pandemic not yet reached.
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A year later,
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when a vaccine against the pandemic H1N1 virus became available,
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we wanted to see what happened.
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After a huge vaccination campaign
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aimed at protecting at-risk groups,
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these hospitals, with 93 percent of the at-risk groups vaccinated,
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had not hospitalized a single patient
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for the pandemic H1N1 virus.
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(Applause)
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In 2009: 251.
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In 2010: zero.
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Vaccination is an act of individual responsibility,
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but it has a huge collective impact.
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If I get vaccinated, not only am I protecting myself,
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but I am also protecting others.
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Sol had whooping cough.
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Sol was very young,
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and she hadn't yet received her first vaccine against whooping cough.
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I still wonder what would have happened
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if everyone around Sol had been vaccinated.
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(Applause)
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