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  • This is the new one-dose Covid-19 vaccine from Johnson & Johnson.

  • In early March, more than 6,000 doses

  • were supposed to be shipped to the city of Detroit, Michigan.

  • But the mayor said, no thanks.

  • "Moderna and Pfizer are the best.

  • And I am going to do everything I can

  • to make sure the residents of the city of Detroit get the best."

  • He was referring to these numbers: the vaccines' "efficacy rates."

  • The vaccines from Pfizer/BioNTech and Moderna have super high efficacy rates:

  • 95 and 94 percent.

  • But Johnson & Johnson? Just 66%.

  • And if you only look at these numbers, it's natural to think that these vaccines

  • are worse than these.

  • But that assumption is wrong.

  • These numbers are arguably not even the most important measure

  • of how effective these vaccines are.

  • To understand what is, you first have to understand what vaccines are even supposed to do.

  • A vaccine's efficacy rate is calculated in large clinical trials,

  • when the vaccine is tested on tens of thousands of people.

  • Those people are broken into two groups:

  • half get the vaccine, and half get a placebo.

  • Then, they're sent out to live their lives,

  • while scientists monitor whether or not they get Covid-19 over several months.

  • In the trial for Pfizer/BioNTech, for example, there were 43,000 participants.

  • In the end, 170 people were infected with Covid-19.

  • And how those people fall into each of these groups determines a vaccine's efficacy.

  • If the 170 were evenly split,

  • that would mean you're just as likely to get sick with the vaccine as without it.

  • So it would have a 0% efficacy.

  • If all 170 were in the placebo group, and zero people who got the vaccine were sick,

  • the vaccine would have an efficacy of 100%.

  • With this particular trial, there were 162 in the placebo group,

  • and just eight in the vaccine group.

  • It means those who had the vaccine were 95% less likely to get Covid-19:

  • The vaccine had a 95% efficacy.

  • Now, this doesn't mean that if 100 people are vaccinated, 5 of them will get sick.

  • Instead, that 95% number applies to the individual.

  • So, each vaccinated person is 95% less likely than a person without a vaccine

  • to get sick, each time they're exposed to Covid-19.

  • And every vaccine's efficacy rate is calculated in the same way.

  • But each vaccine's trial might be done in very different circumstances.

  • "So, one of the biggest considerations here, when we look at these numbers,

  • is the timing in which these clinical trials were performed."

  • This is the number of daily Covid-19 cases in the US since the pandemic began.

  • The Moderna trial was done completely in the US, here, in the summer.

  • The Pfizer/BioNTech trial was primarily based in the US, too, and at the same time.

  • Johnson & Johnson, however, held their US trial at this time,

  • when there were more opportunities for participants to be exposed to infections.

  • And most of their trial took place in other countries, primarily South Africa and Brazil.

  • And in these other countries, not only were case rates high,

  • but the virus itself was different.

  • The trials took place as variants of Covid-19 emerged,

  • and became the dominant infections in these countries;

  • variants that are more likely to get participants sick.

  • In South Africa, most of the cases in the Johnson & Johnson trial were that of the variant,

  • not the original strain that was in the US over the summer.

  • And despite that, it still significantly reduced infections.

  • "If you're trying to make one-to-one, head-to-head comparisons between vaccines,

  • they need to have been studied in the same trial, with the same inclusion criteria,

  • in the same parts of the world, at the same time."

  • "If we were to take Pfizer and Moderna's vaccines,

  • and redo their clinical trial at the same time that we saw J&J's clinical trial,

  • we might see quite different efficacy numbers for those."

  • These efficacy numbers really just tell you what happened in each vaccine's trial,

  • not exactly what will happen in the real world.

  • But many experts argue this isn't even the best number to judge a vaccine by anyway.

  • Because preventing any infection at all is not always the point of a vaccine.

  • "The goal of a vaccine program for Covid-19 is not necessarily to get to 'Covid zero,'

  • but it's to tame this virus, to defang it,

  • to remove its ability to cause serious disease, hospitalization, and death."

  • It helps to look at the different outcomes of an exposure to Covid-19 like this:

  • The best-case scenario is, you don't get sick at all.

  • The worst case is death.

  • In between, there's being hospitalized, severe-to-moderate symptoms,

  • or having no symptoms at all.

  • In the absolute best circumstances, vaccines give you protection all the way to here.

  • But realistically, that isn't the main objective of Covid-19 vaccines.

  • The real purpose is to give your body enough protection to cover these possibilities,

  • so if you do get an infection, it feels more like a cold

  • than something you'd be hospitalized for.

  • And this is one thing that every one of these Covid-19 vaccines do well.

  • In all these trials, while some people in the placebo groups were hospitalized,

  • or even died from Covid-19,

  • not one fully vaccinated person, in any of these trials,

  • was hospitalized or died from Covid-19.

  • "One thing that I wish that mayor would have understood,

  • was that all three vaccines have essentially 100% effectiveness in protecting from death."

  • The mayor of Detroit did backtrack, and said he'd start taking Johnson & Johnson doses,

  • because it's still "highly effective against what we care about most."

  • Efficacy matters. But it doesn't matter the most.

  • The question isn't which vaccine will protect you from any Covid infection,

  • but which one will keep you alive?

  • Or out of the hospital?

  • Which one will help end the pandemic?

  • And that's any of them.

  • "The best vaccine right now for you is the one that you're offered."

  • "With each shot that goes into someone's arm, we get closer to the end of this pandemic."

This is the new one-dose Covid-19 vaccine from Johnson & Johnson.

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Why you can't compare Covid-19 vaccines

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    林宜悉 posted on 2021/03/20
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