Oct. 8, 2021 -- The protection from Pfizer’s COVID-19 vaccine may begin to wane against infection after 2 months, but it still prevents hospitalization and death for at least 6 months, according to two new studies published Wednesday in TheNew England Journal of Medicine.

The new findings support what Pfizer, the CDC, and top health officials have said in recent weeks: Initial protection against getting the coronavirus itself may drop over time, but people who get the vaccine avoid the worst effects of severe disease.

In the first study, researchers in Qatar estimated vaccine efficacy against COVID-19 infection and severe, critical, or fatal cases between Jan. 1 and Sept. 5. They based the report on infections among 900,000 vaccinated people in Qatar.

After the first Pfizer dose, protection against infection was “negligible” for the first 2 weeks but jumped to about 37% in the third week. Protection then reached a peak of about 78% in the first month after the second dose.

Efficacy fell gradually after that, with the decline speeding up after the fourth month. For some people who got the vaccine, protection dropped as low as 20% between 5 and 7 months after the second dose.

“These findings suggest that a large proportion of the vaccinated population could lose its protection against infection in the coming months, perhaps increasing the potential for new epidemic waves,” the researchers wrote.

The effectiveness against symptomatic infection was higher than the effectiveness against asymptomatic infection, but both rates waned over time, the researchers wrote. A similar pattern was seen for the different variants, including the Beta and Delta variants.

Effectiveness against severe, critical, and fatal COVID-19 cases increased to 66% by the third week after the first dose and reached 96% in the first 2 months after the second dose. The protection lasted at this level for about 6 months.

How Do COVID-19 mRNA Vaccines Work?Some of the COVID-19 vaccines are known as mRNA shots. How are they different from traditional vaccines? And do they contain the real virus?189

[MUSIC PLAYING]

SPEAKER: How does a COVID-19

mRNA vaccine work?

COVID vaccines are now

available.

Some of the COVID-19 vaccines

are mRNA vaccines, but what does

this mean?

mRNA vaccines are

different from traditional

vaccines.

mRNA vaccines don't expose you

to any real virus instead,

they're made with messenger

Ribonucleic Acid or mRNA.

This is a type of molecule that

gives instructions to the cell

for how to make different kinds

of proteins.



mRNA molecules are

a natural part of our cells

and how our bodies work.

Researchers have been working

with mRNA vaccines

for many years.

They are made more easily

and safely in a lab

than a vaccine that uses

a virus.

Because of this they can also

be made faster.

The COVID-19 mRNA vaccines

have passed many tests in labs

and in thousands of people,

and meet strict standards

from the FDA.



So how do these vaccines work?

First, a COVID-19 mRNA vaccine

is injected into a muscle

in your upper arm.

Some muscle cells take the mRNA

instructions in the vaccine

and make a harmless piece

of a protein called

a spike protein.

This protein is found

on the outside of the SARS-CoV-2

virus that causes COVID-19.



The muscle cells then destroy

the instructions for how to make

the spike protein.

The mRNA never goes

into the nucleus of your cells

where your DNA is stored.

The newly made spike protein now

sits on the surface

of the muscle cells.



Your immune system senses

the spike protein

as a foreign threat to destroy,

it starts making antibodies

to fight anything

with that spike protein on it.

This will help your body's

immune system recognize

and fight the real virus if it

ever shows up.

It's like recognizing someone

by the hat they wear.

Your body is then

prepared to spot COVID-19

and fight it off before it grows

in your body's cells.



Fast facts to remember

about COVID-19 mRNA vaccines.

They help get your body

ready to fight off the COVID-19

virus before it makes you sick,

they don't use

any live, dead, or weak virus,

they can't give you COVID-19,

they don't affect your DNA.

Want to learn more,

go to cdc.gov to find more

information about mRNA vaccines.

You can also learn more about

how the vaccines were approved

at fda.gov.



[SWOOSH]



[MUSIC PLAYING]



From Krames/delivery/aws/e1/19/e1194689-aff0-4d9e-9fd2-2c0084642589/b37084c0-2e1f-4b66-958c-96e7a6c3f4db_krames_activating_health_how_mrna_vaccine_works_021021_,4500k,2500k,1000k,750k,400k,.mp402/10/2021 12:00:0018001200photo of COVID-19 mRNA vaccine/webmd/consumer_assets/site_images/article_thumbnails/video/1800x1200_krames_activating_health_how_mrna_vaccine_works_video.jpg091e9c5e8210a400

“Protection against SARS-CoV-2 infection appeared to wane rapidly following its peak after the second dose, but protection against hospitalization and death persisted at a robust level for six months after the second dose,” the researchers wrote.

In the second study, researchers in Israel looked at COVID-19 antibodies among more than 4,800 health care workers who were tested regularly after vaccination. Among those, 20 had breakthrough infections.

The research team found that the level of antibodies circulating in the blood decreased at a consistent rate over 6 months. The level of neutralizing antibodies, which correlates with protection, decreased rapidly in the first 3 months but then slowly declined after that.

Six months after the second dose, neutralizing antibodies were substantially lower among men than women. They were also lower for people ages 65 and older and those with weak immune systems.

Neutralizing antibodies were significantly higher in those who had a body mass index of 30 or above. But the researchers said it’s unclear whether the higher level is more protective and whether vaccinated obese people face higher or lower risks for breakthrough infections.

“As this pandemic continues to evolve, the importance of determining immune correlates of protection after vaccination becomes clearer,” the researchers wrote. “Strategies to prolong host immunity need to be evaluated in order to protect the population against SARS-CoV-2 and its variants.”

Show Sources

The New England Journal of Medicine: “Waning of BNT162b2 Vaccine Protection against SARS-CoV-2 Infection in Qatar,” “Waning Immune Humoral Response to BNT162b2 Covid-19 Vaccine over 6 Months.”

© 2021 WebMD, LLC. All rights reserved. View privacy policy and trust info