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  • (pensive music)

  • - [Narrator] Throughout the pandemic,

  • athletes have been the most tested population

  • on the planet, sometimes providing examples

  • of emerging theories about COVID-19.

  • And as countries around the world continue

  • to fight back COVID-19,

  • attention has turned to Tokyo

  • where the Olympics are under way.

  • One challenge some athletes are facing:

  • testing positive for the virus,

  • despite having been vaccinated.

  • This isn't the first we've heard of this.

  • - What are chances of getting COVID-19

  • after receiving a vaccine?

  • Well, you've got a better chance

  • of buying a winning lottery ticket

  • but it happened to Warriors player Damion Lee.

  • - [Reporter 1] He will be out at least two weeks.

  • It was not a false positive as first thought,

  • even though Walman had been vaccinated.

  • - [Reporter 2] Yankees GM Brian Cashman says

  • that three players tested positive

  • and three others are likely infected.

  • About 85% of the team is vaccinated,

  • including those who have the virus.

  • - [Narrator] These examples are known

  • as breakthrough infections,

  • which occur when someone tests positive

  • for COVID-19 at least two weeks after getting

  • their final shot.

  • Do these breakthrough cases mean the vaccines are failing?

  • - No, the vaccines are not failing.

  • The vaccines are working extremely well,

  • and as expected.

  • They do protect the majority of recipients

  • from severe disease.

  • - [Narrator] That's what vaccines are designed to do:

  • Prevent death and severe disease.

  • But most vaccines, including those created

  • to fight COVID-19

  • don't completely protect you from infection.

  • So it's not all that surprising

  • that breakthrough infections are showing up.

  • As of July 12th, more than 159 million people in the US

  • have been fully vaccinated.

  • CDC data suggests just under 5,500

  • have had breakthrough infections,

  • resulting in hospitalizations or deaths.

  • That's one in approximately 29,000 people

  • who have been vaccinated.

  • - Breakthrough infections are something

  • that we want to monitor

  • but in terms of their overall influence in the pandemic,

  • they play a much smaller role

  • than transmission among people who haven't been vaccinated.

  • - [Narrator] But these cases raise questions

  • about our immunity to the virus

  • and hint at a future in which it isn't gone completely

  • and we learn to live with it.

  • That's due in part to variants.

  • Research shows that variants,

  • including Delta, can partially evade the immune response

  • from prior infection and vaccination.

  • - We mount a really good immune response

  • against the virus that our body's trying to recognize.

  • Your body is really good

  • at recognizing and neutralizing those specific threats.

  • But when the virus starts to change,

  • sometimes it doesn't recognize the virus as well.

  • And so that's how you sort of see it chip away

  • at that immune response.

  • That's one of the reasons that health officials

  • are really sort of concerned

  • about this global vaccination drive

  • in order to prevent the virus from spreading,

  • both to save lives

  • and to prevent it from further mutating

  • and evading immune response.

  • - [Narrator] The Delta variant

  • is the most contagious version

  • of the virus to be identified,

  • but research suggests that full vaccination

  • is still protective against severe disease and death:

  • the outcomes that have made COVID-19 so devastating.

  • What dictates whether someone is more likely

  • to get infected, even if they're vaccinated?

  • Dr. Hatziioannou says there are four main variables.

  • First is the amount of virus that is circulating

  • in your community.

  • - So if a great number of people around you are infected,

  • then the possibility

  • of you getting exposed obviously increases.

  • If you're in close proximity with people

  • that are infected,

  • particularly those that are unvaccinated

  • and have generally higher viral loads,

  • then the probability of you getting infected increases.

  • - [Narrator] The second is tied to vaccine uptake.

  • - So if a large proportion of the population is vaccinated,

  • then your virus transmission,

  • virus loads, everything decreases.

  • So the chances of spreading the virus

  • amongst this population obviously decreases.

  • - [Narrator] That's because vaccinated people act

  • as a kind of shield,

  • even when they do get infected.

  • A recent CDC study found that vaccinated people

  • carried less virus and potentially didn't spread it

  • as much as unvaccinated people.

  • Cases were also shorter and less severe.

  • Vaccines help create a kind of immune memory

  • of what a virus looks like,

  • helping the body fight it off more quickly

  • when it spots it.

  • That makes it harder for the virus to spread overall.

  • Roughly half of all Americans are fully vaccinated

  • but in some states and globally,

  • the vaccination rate is much lower,

  • giving the virus more opportunity to spread and mutate.

  • That's why having large gathering,

  • like concerts or the Olympics can be so challenging

  • from a public health perspective.

  • Third, individual behavior matters.

  • - So as measures have been abandoned,

  • such as masking and social distancing,

  • when you don't have a significant number

  • of the population vaccinated,

  • then the ability of the vaccines to protect you

  • from getting infected decrease.

  • - [Narrator] Finally, even after vaccination,

  • individual immune systems vary in their ability

  • to prevent and fight off infection.

  • Older and immunocompromised people seem

  • to be more susceptible to breakthrough cases,

  • and those tend to be severe.

  • - That's why health officials

  • are considering additional doses right now,

  • primarily for people who have a compromised immune system

  • and might not have produced a good immune response

  • after two doses of the vaccine.

  • - [Narrator] Breakthrough cases might be asymptomatic

  • or mild, so people may not know to get tested.

  • But that's not the case for athletes.

  • - We're actually seeing breakthrough infections happen

  • a lot more amongst sports teams,

  • like baseball or for the Olympics

  • because those are the people

  • that get tested pretty regularly,

  • even if they're vaccinated.

  • - [Narrator] At the Olympics,

  • organizers of the games are scrambling

  • to deal with a rising load of athletes and officials

  • who are testing positive upon arrival in Japan,

  • some with breakthrough infections.

  • The vaccination rates are low in Japan.

  • Cases there are rising

  • and organizers didn't require those participating

  • to get vaccinated.

  • Dr. Hatziioannou and many other experts remain concerned

  • that holding a large-scale international event prior

  • to reaching a critical mass

  • of vaccinated individuals has the potential

  • to contribute to the virus's spread around the world.

  • - The Olympics is a special event

  • and it's truly remarkable

  • that it brings all these people

  • from all these different countries together

  • but it also poses a perfect ground

  • to mix variants and spread the virus

  • that will then go back to each athlete's country.

(pensive music)

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Breakthrough Covid-19 Cases Raise Questions About Immunity | WSJ(Breakthrough Covid-19 Cases Raise Questions About Immunity | WSJ)

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    moge0072008 發佈於 2021 年 07 月 29 日
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