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Why the second dose of the coronavirus vaccine is so important

2021-02-05T20:13:06.193Z


The so-called primary booster vaccines, those that work best with two or more doses, to boost the body's immune system.


Is immunity lost if a second dose is not received?

4:01

(CNN) -

Imagine that you finally received your coronavirus vaccine.

You waited several weeks, maybe a few calls, before you hit the jackpot at a vaccination clinic.

Or maybe you are a healthcare worker who got the vaccine at work.

Now for the hard part: making sure you get your second dose on time.

It means another appointment and keeping an eye on the calendar.

Also, perhaps, a little anxiety.

Doctors have been warning people that the first dose can have an effect.

And now, people are starting to report that the second dose can cause more side effects than the first dose.

It is not an unexpected find.

Moderna and Pfizer said in their submissions to the US Food and Drug Administration (FDA) that there was a noticeable difference in dose reactions when they were testing their vaccines in volunteers.

"Local adverse reactions collected grade 3 were reported more frequently after dose 2 than after dose 1," says Moderna's statement.

Grade 3 adverse reactions include swelling, pain, body aches, headache, and fever.

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An analogy to understand how the second dose works

But why?

Analogies always help.

Imagine you look out your window one night and see someone loitering.

It looks creepy and you might be a little alarmed, but don't panic.

“The first time someone sees this peeping person, they may be quite scared.

They might go to the police station and report this person and someone will draw a sketch and that will go to all the police stations, ”says University of Arizona Professor of Evolutionary Biology Michael Worobey.

A few weeks later, he hears a noise, looks out the window, and sees the same face.

He is more likely to react strongly this time, knowing that he has seen this face before.

Your heart is pounding, your hands get wet, and your mind races.

You can even call 911. And the police will be ready to grab the guy.

"The next time that person tries to do something, there will likely be a much bigger response because now more people are familiar with that face," explains Worobey.

The first dose of vaccine is like the first look at the stranger: the body's immune system takes notice and takes some precautions, but the second time is even more prepared to recognize and respond to that indication.

This is how vaccines work in general, of course.

They are meant to be like a wanted poster, educating the immune system to be on the lookout.

So-called primary booster vaccines, those that work best with two or more doses, elicit this response.

"With the first dose, you should generate an immune response from scratch," said Worobey.

The body produces antibodies, but it also begins to generate immune cells called B cells to produce targeted antibodies.

This takes time, a process known as ripening.

"You end up with a finely tuned B cell population," said Worobey.

“Then the second time you give a person the injection, those cells are sitting like an army of clones and can immediately start to produce a huge immune response, which is what happens when people feel like they have been kicked. on the teeth.

Thomas Geisbert, professor and expert in Emerging Viral Threats in the medical branch of the University of Texas, points out that some vaccines generate a great response with a single dose.

But the main push strategy builds a more durable defense force, he says.

"Your immune system is already activated from the first dose," he said.

Then, with a second dose, "you tend to develop a longer and lasting response."

The flu-like symptoms that accompany any viral infection are not caused by the virus itself.

They are caused by the body's response.

Fever and muscle aches come from inflammation, which in turn is a signal that immune cells called T cells are sending out an alarm in the form of signaling chemicals called cytokines.

"It swells at the injection site," Geisbert said.

"People may have chills or aches and pains, or feel sick or tired."

That bodes well for predicting whether vaccines will provide better protection than natural immunity.

"These symptoms mean that your immune system is picking up and the vaccine is really working," said the director of the US Centers for Disease Control and Prevention, Dr. Rochelle Walensky, in a briefing at the Casa Blanca, last month.

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More information on immunity and coronavirus is still to be expected

The new coronavirus has only been around for about a year, so no one can say yet whether it will be more like measles, which people get once in a lifetime, or like the flu, which people get over and over again.

Studies indicate that immunity to the coronavirus lasts for months anyway - six months, nine months, or even longer.

That's not in 100% of the population: immunity varies greatly from person to person, and some cases of people infected twice by coronavirus have been documented.

But they seem to be rare cases.

These studies also take snapshots of people's immune systems over time and show that immediately after infection, two types of antibodies increase in number and then collapse, while a third type builds up more slowly.

And then the B cells that have been "trained" to recognize the virus begin to produce specific antibodies that build up in the blood.

Vaccination can speed up this process, giving people faster protection, but perhaps also providing a broader level of protection than a natural infection.

"Because this is all going so fast, the studies and key data are not there yet," Geisbert said.

Covid-19 Coroavirus Vaccine

Source: cnnespanol

All news articles on 2021-02-05

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