As the coronavirus continues its spread around the globe, more people are becoming vaccinated. One of the primary questions about vaccination on most people’s minds is how long they are immune once they have all the shots they need.
Many infectious disease experts believe that the effectiveness of the vaccines drops over time. For this reason, research into these concerns continues. According to the Centers for Disease Control and Prevention, studies show that effectiveness against infection drops from 91.8% to 75% over time.
However, COVID-19 vaccines do not become completely ineffective — they continue to prevent infection but have a reduced ability to do so. Learn more about each of the COVID-19 vaccines in the U.S., how long they last, and whether you’ll need a booster to maintain your immunity.
How Long Do COVID-19 Vaccines Take to Work?
Vaccinations against the COVID-19 virus are administered in different doses, depending on who created it. The Moderna and Pfizer (now also called Comirnaty) immunizations are designed to be administered in two shots, while the Johnson & Johnson (now also called Janssen) vaccine only needs to be given once.
If you've gotten the Moderna or Pfizer shot, you have to wait a specific number of days before getting the second shot, and each of the three shots takes a different amount of time to reach full effectiveness.
Here’s a run-down of each shot and the waiting periods between them:
- Moderna: You have to wait 28 days between shots. After two doses, it takes two weeks after your second shot to be 90% effective against infection and 95% effective against developing a severe case if you contract the virus.
- Pfizer (Comirnaty): You’ll need to wait 21 days between shots. Pfizer/Comirnaty is 95% effective in preventing infection within two weeks of your second shot and 90% effective against developing a severe infection.
- Johnson & Johnson: Johnson & Johnson’s Janssen single dose is 72% effective in the prevention and 86% effective against developing a severe infection. It takes your body 14 days to develop immunity after one dose.
How Long Are You Immune?
The information we have currently makes it difficult to state the length of time you’ll be immune. People’s bodies all respond differently to the vaccines, so the CDC and pharmaceutical companies are working diligently to understand how long immunity lasts.
In a nutshell, it comes down to your body’s antibody production. When you get your shot, your body produces antibodies that work to fight COVID-19. Antibodies are proteins the body creates that fight viruses and bacteria. Once the antibodies are created, they continue to work inside your system to fight the virus.
Once the antibodies are created, they fight to keep you from becoming infected. As the virus dies off, antibody production slowly wanes because your immune system is winning.
The decline in antibody production seems slow enough that doctors think the vaccines will protect you for up to least one year. People with underlying conditions or who might have some immuno-compromising conditions might not be protected for as long; protection varies from person to person.
Is Your Vaccine Good Against New Strains?
It is well-documented that COVID-19 vaccinations provide protection from the strains they were designed to fight. It is not as clear if they work as well against new strains or virus mutations.
According to the CDC, the more people that are vaccinated, the fewer chances the virus has to spread and mutate. This means that the odds of contracting the most recent variant, Delta, are significantly reduced if you’re vaccinated. You’re also less likely to experience severe illness from the Delta variant if you’ve received your shots.
Will You Need a COVID-19 Booster Shot?
The jury is still out on whether you might need a booster. However, booster shots are recommended for anyone with an underlying health condition or a compromised immune system. Booster shots act exactly the way their name implies — they boost the effectiveness of your previous shots by restarting the antibody creation process.
When you get a booster, the effectiveness of your original vaccination returns to its maximum level. According to the CDC, more than 194 million people are fully vaccinated against COVID-19. Of those 194 million, 12% (25 million) received booster shots. More than 50% of that group are aged 50 or higher.
It’s important to note that the CDC says that people with vaccinations are less likely to become infected and or need hospitalization. However, you can still contract the virus even after you’re immunized.
When a virus infects you after you’ve been fully vaccinated, it is called a breakthrough infection. Since the vaccines are not 100% effective, breakthrough infections can happen; they just have a lower chance of occurring. Breakthrough infections are also less likely to require hospitalization since the risks of severe infections are reduced by full immunization.
However, if you want to be more cautious, have a condition that puts you more at risk, or your doctor suggests that you get a booster shot, the CDC recommends that you get one to be safe.
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Centers for Disease Control and Prevention. “COVID-19 Vaccinations in the United States,” “How to Talk with Patients Who Are Immunocompromised,” “Moderna COVID-19 Vaccine Overview and Safety,” “New COVID-19 Cases and Hospitalizations Among Adults, by Vaccination Status — New York, May 3 – July 25, 2021,” “Pfizer-BioNTech COVID-19 Vaccine Overview and Safety (also known as COMIRNATY),” “The Possibility of COVID-19 after Vaccination: Breakthrough Infections,” “What You Need to Know about Variants.”
National Human Genome Research Institute: “Antibody.”
Yale Medicine. “How Long Will Your Coronavirus Vaccination Last?”
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