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  • This episode was filmed on February 9th, 2021.

  • If we have any updates about COVID-19  vaccinations or the pandemic in general,

  • they'll be in the playlist  linked in the description.

  • [♪♪♪]

  • With the COVID-19 vaccines finally  getting into people's arms,

  • you might've heard that your second dose  might feel a little rougher than the first.

  • And it's true. Participants in clinical  trials, plus the recently vaccinated public,

  • saw more frequent and more intense side  effects on their second jab than their first.

  • This is actually a sign that the  vaccines are working properly.

  • So while you should prepare to feel crummy  for a couple days, it's a good thing overall!

  • And it might hint at the  possibility of more good news:

  • that people who've recovered from  COVID-19 could only need one shot!

  • The key thing to understand is  that these reactions to vaccines,

  • things like fever, chills, and other side-effectsaren't really from the vaccine itself.

  • They're natural byproducts of your  immune system learning to fight

  • the germ the vaccine is teaching it to spot.

  • And that response is stronger  after the second shot

  • because the first shot did  what it was supposed to do!

  • To understand what I mean, let's have  a quick refresher on how vaccines work.

  • In general, vaccines teach your  immune system to spot a pathogen

  • by giving it some harmless version  or just part of it to study.

  • That way, if ever encounters a real  deal, it'll know how to fight it.

  • We call this adaptive immunity —  but it doesn't happen immediately.

  • It takes weeks to fully develop the strongtargeted response that vaccines are aiming for.

  • So the first time a vaccine introduces  your immune system to a new pathogen,

  • any discomfort you feel is something  else: your innate immunity kicking in.

  • This is a generalized first line of defense that  attacks anything the body perceives as a threat.

  • And it can definitely have some  uncomfortable side effects.

  • For instance, within a few hoursyou can have local reactions,

  • which are things like pain and  redness at the injection site

  • or tenderness in the armpit of the  arm that received the injection.

  • You can also have systemic  reactions that point to a

  • more widespread activation of your immune system.

  • These are symptoms like fatigueheadache, and all over muscle pain.

  • But often, these side-effects are  minor, or maybe not noticeable at all.

  • What matters is what's  happening in the background.

  • While your innate immunity is doing its thing,

  • the immune cells that do the  heavy lifting in adaptive immunity  

  • are studying the foreign material

  • and building up targeted weapons like antibodies.

  • That way, by the time you get  your second dose of the vaccine,

  • your adaptive immunity has the  tools it needs to fight the invader.

  • And it does.

  • That, too, can set off local  and systemic reactions.

  • So following your second shot, you get both  innate and adaptive immunity acting at once!

  • Which is why the side effects  are often more severe.

  • This strong, dual immune  reaction also ensures your body

  • takes the threat seriously and ramps  up its defenses against it even more.

  • So as much as we dislike  the potential side-effects,

  • the result is lasting protection from the virus.

  • Now, some people get the  short end of the stick here.

  • Thanks to their unique  experiences and genetic makeup,

  • they really feel it when their immune  system gets riled up, while others don't.

  • And we don't totally know why.

  • But, if you're going to feel crummy, the odds  are higher it'll happen in dose number two.

  • And that's not newsthat's exactly what was  seen in the clinical trials for these vaccines.

  • For example, across all age  groups in the Moderna trial,

  • more participants reported some  kind of local or systemic reaction

  • on their second dose of the vaccine.

  • And something similar was seen with the BioNTech  vaccine, now being distributed by Pfizer.

  • While pain at the injection site was  more common after the first dose,

  • the researchers noted more redness  and swelling after the second dose,

  • as well as more body-wide reactions  like fatigue, fever, and muscle pain.

  • Thankfully, in trials, these effects almost  always went away after two or three days.

  • There's also nothing really special  about the side effects occurring now.

  • You're hearing about them because lots of  people are getting vaccinated all at once,

  • and this is a really big dealand everyone is talking about it.

  • But these side effects are on  par with what's seen following

  • other multi-dose vaccines given to adults.

  • Take Shingrix, for example—a shingles vaccine  you might get if you're over 50 years old.

  • Most people get a sore arm, while some  feel fatigue, headaches, or muscle pain

  • that lasts a couple of days.

  • That said, some people who've already had  COVID-19 are reporting something different:

  • they seem to be having those stronger,  “second-doseside effects after dose one.

  • That may be because the disease itself  can act kind of like a first vaccine dose,

  • in that it teaches the immune  system to spot the virus.

  • So, the first dose of the vaccine may be having  similar effects to everyone else's booster.

  • What's nifty about that is that it  could mean they only need one dose.

  • To be clear, the vast majority of the  clinical trials for these vaccines

  • have only used a two-dose vaccination strategy.

  • So no one has tested this one-vaccine hypothesis!

  • But two recent preprint articles  concluded that we might be able to

  • reallocate the limited doses of the  mRNA vaccines being distributed by

  • Pfizer and Moderna without compromising safety.

  • One found that people who had  recovered from COVID-19 developed

  • at least ten times as many  antibodies after one dose of

  • an mRNA vaccine as previously  healthy people who got two.

  • And the other found that healthcare  workers who had previously had COVID-19

  • had antibody levels on par with folks  who got two doses of the mRNA vaccines

  • but had never been infected.

  • That might mean that previously  infected individuals might only need

  • one shot to protect them long term!

  • And if that's the case, we may be able to  give that second vaccine dose to someone else,

  • and hopefully get people vaccinated even faster.

  • Now, each of these studies only  had a few hundred participants,

  • and neither has been peer-reviewed, so we  can't start making sweeping statements yet.

  • And there are no changes in policy or anything.

  • So, in the meantime, keep doing what your  medical professionals tell you to do!

  • Still, if you have had COVID-19, be warned  your first vaccine shot could be the rough one.

  • And for everyone else, it might be helpful  to set your expectations ahead of time.

  • Yes, there's a good chance you'll feel  bad after your second dose in particular,

  • and need to take a day or  two to rest and recuperate.

  • But it'll be worth it, because these  expected temporary side effects are

  • way less intense and debilitating  than getting a bad case of COVID-19,

  • and we all just want to get through this  pandemic so we can relax a little bit.

  • Thanks for watching this episode of SciShow News!

  • We're here every Friday with an  update from the world of science.

  • So if you want to stay informed, be sure to  subscribe and click on that notification bell.

  • And if you have further questions about  the vaccines being rolled out in the US,

  • you might want to check out our deep  dive into the history of mRNA vaccines.

  • You can find it and all our  latest episodes regarding

  • the COVID-19 pandemic in the  playlist linked in the description.

This episode was filmed on February 9th, 2021.

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Second COVID Vaccine Shot Side Effects

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    joey joey posted on 2021/06/03
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