What Is The Difference Between A Third Dose And A Booster Shot
A booster dose, on the other hand, is intended to offer a boost of immunity a certain period of time after original vaccination because there is evidence that the effectiveness of the vaccine wanes over time. Learn more about booster doses.
A third dose of an mRNA vaccine is recommended for people who are immunocompromised, and it should be given at least 28 days after the second dose. The third dose is recommended because there is evidence that this group doesnt build up the same level of immunity after two doses. Learn more about third doses.
Why Is A Third Shot Of A Covid
The CDC recommends a third dose of the two-shot vaccines for people with certain health conditions to help further protect them from getting severely ill or dying due to COVID-19. Some people have conditions or take specific medication doses that can cause them to have a decreased immune system. Data suggest that two doses of the mRNA COVID-19 vaccine may not have a strong enough response in these individuals, and that they may benefit from a third dose.
How Does Immunity From A Vaccine Compare To Immunity From Infection
Vaccine-induced immunity and natural immunity both provide protection against getting the infection in the future. Which one provides better immunity can depend on the type of infection it is.
We are still learning about COVID-19 and immunity, but a recent study showed that vaccine-induced immunity was better than natural immunity in protecting against COVID-19. Getting the vaccine also allowed the immune system to recognize other coronavirus strains, which could provide protection against new variants that develop.
An important advantage of any vaccine-induced immunity is that you can get immunity without actually getting sick. For COVID-19, this is especially important because even if you recover from it, many people continue to have debilitating symptoms for months.
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Coronavirus Measures Still Needed After Vaccination
7 to 14 days after full vaccination with one of the COVID-19 vaccines , 60-90% of vaccinated people are protected against COVID-19. This means that not everyone is protected. The chance of getting COVID-19 after full vaccination is very small, but not zero. If you do get COVID-19, your illness will usually be less serious. It is still important to follow the general coronavirus rules, even after vaccination.
It Takes Time For The Vaccination To Provide Immunity

Clinical studies indicate that the vaccination may provide some protection around 12 days after the first dose is given, but you must get both doses in order to achieve full protection. When both doses are administered, the vaccine is more than 90% effective at preventing COVID-19 infection.
On May 13, the CDC stated that people who are fully vaccinated no longer need to wear masks or maintain social distancing in most situations. However, the CDC also noted that people with weakened immune conditions, such as cancer, should talk to their healthcare provider about the need for protective measures even after vaccination. Therefore, to protect our patients from COVID-19, MSK requires that all staff, patients, and visitors must continue to wear masks while at MSK. This requirement includes people who are fully vaccinated.
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Even If Youre Fully Vaccinated Its Important To Continue To Take Precautions
Although getting vaccinated is an important step in protecting people from COVID-19, it does not mean they can stop practicing precautions such as masking, social distancing, and hand hygiene. Those measures are still critical as we continue to battle the pandemic. Right now theres so much COVID circulating, getting the vaccines doesnt mean you can go back to life as before, says Dr. Marks. I think its important to continue to take all the recommended precautions, so you can protect yourself and others. Until we really get a decrease in the COVID thats circulating, all of that remains necessary.
Note: Following CDC, FDA and New York State guidance, NewYork-Presbyterian has resumed the use of the Johnson & Johnson COVID-19 vaccine, in addition to continuing to offer the Pfizer and Moderna vaccines.
If you received the J& J vaccine within the last three weeks and develop severe headache, abdominal pain, leg pain, or shortness of breath, please contact your health care provider.
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How Long Vaccine Immunity Lasts
After the imitation infection goes away, your body still remembers the infection and how to fight it. Some vaccines, like ones for measles or hepatitis B can make you immune forever. For others, immunity may wane in time, and this is likely the case with SARS-CoV-2. But how long does immunity last?
The starting baseline seems to be from 8 months up, for most people. A recent study published in Science found that most people still have a clear detectable level of immunity after 8 months. Another study has shown that antibody levels dont seem to decline after 4 months in people whove had the disease, and vaccines seem to offer much longer protection to the disease than an infection. When we put all this together, we end up with an optimistic picture: antibodies decline at a very slow rate, and could therefore last for a very, very long time maybe several years.
That amount of memory would likely prevent the vast majority of people from getting hospitalized disease, severe disease, for many years, said Shane Crotty, a virologist at the La Jolla Institute of Immunology who co-led the study, for the New York Times.
Matters become complicated because its not just antibodies memory B cells, helper T cells, killer T cells can all remember and fight the coronavirus.
So were in a timeline varying from we could need vaccination every year and immunity could last for several years. Unfortunately, finding a more accurate estimate will require more time and research.
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How Quickly Immunity Sets In
Vaccines develop your immunity by imitating an infection, without actually exposing you to the virus. Sometimes, the imitation infection can cause some minor symptoms, but thats not an actual infection just the body building up immunity . According to the CDC, it typically takes a few weeks after vaccination to achieve immunity. This is after the second dose, if its a two-dose vaccine.
For some vaccines , studies have shown that more than one dose is needed for everyone to develop the best immune response. For example, after one dose of the MMR vaccine, some people may not develop enough antibodies to fight off infection. The second dose helps make sure that almost everyone is protected, the CDC notes.
Because it can take a while for immunity to kick in, this means that someone who was infected right before getting the vaccine could develop symptoms and get the disease.
This period before immunity kicks in can vary between different vaccines. For instance, Pfizer measured its reported 95% efficacy starting 7 days after the second dose, while Moderna measured it 14 days after the second dose. So if you want to enjoy the full immunity offered by the vaccine, youd still have to wait a couple of weeks.
To a lesser extent, the first dose also provides immunity in some people. For instance, one recent study found that protection from taking the first dose of the Pfizer vaccine only starts after 12 days, increasing to 52% a few weeks later.
Who Can Get A Third Dose Of A Covid
Based on CDC recommendations, third vaccine doses are available now for people who are considered moderately or severely immunosuppressed. These would include those who:
- Receive active cancer treatment for tumors or cancers of the blood.
- Received an organ transplant and are taking medicine to suppress the immune system.
- Have either had a stem cell transplant within the last two years or are taking medicine to suppress the immune system.
- Were diagnosed with DiGeorge syndrome or Wiskott-Aldrich syndrome.
- Are diagnosed with HIV and have a high viral load or low CD4 count, or are not currently taking medication to treat HIV.
- Are taking drugs such as high-dose steroids or other medications that may cause severe suppression of the immune system.
If you are not sure whether you fit into any of these categories, please contact your medical provider.
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How Effective Is The Covid
As with any vaccine, the Pfizer vaccine may not fully protect everyone who gets it. However, it is highly effective if people have both doses. That means, if you do catch COVID-19, youre far less likely to fall seriously ill and less likely to transmit the virus to others.
The COVID-19 vaccine stimulates your bodys immune system to produce antibodies and other proteins that will fight the virus if youre exposed to it. This reduces the risk of getting infected and if you do get COVID-19, it means you could have no symptoms or will have much fewer, milder symptoms and recover faster.
While the data is clear that vaccines protect people from the effects of COVID-19, research is ongoing to determine whether a vaccinated person could still transmit the virus to someone else so to be safe, we must assume there is still a risk of transmission.
Am I Eligible For A Third Dose Of The Covid
In the United States, people with weakened immune systems are eligible for a third dose of the COVID-19 vaccine along with people who are 65 and older and those who live or work in certain high-risk settings. While the criteria will most likely change, this group currently includes patients whove had or are receiving:
- Organ transplants
- Stem cell transplants within the past two years
- Active cancer treatment for tumors or blood cancer and are undergoing chemotherapy that affects the immune system
- Severe primary immunodeficiency
- Advanced or untreated HIV
- Active treatment with high-dose corticosteroids or other drugs that may suppress your immune response.
There is not enough data yet to know whether immunocompromised people who got the one-dose Johnson & Johnson vaccine need another dose, but we expect to know more soon.
You are not eligible for a third dose of the vaccine at this time if you are healthy, do not have one of these specific conditions, do not take certain immunosuppressive medications, are under 65, or do not live and work in a high-risk setting.
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Why Are Booster Doses Recommended
The protection of some vaccines lessens over time as the bodys antibody levels drop. In those cases, an extra dose of vaccine can refill the antibody tank and boost the immune response. Thats why booster shots are recommended for tetanus, for example.
The COVID-19 vaccines remain effective in reducing risk of severe disease, hospitalization and death, even against the Delta variant. However, the CDC has found that the COVID-19 vaccines protection against mild to moderate disease decreases over time. Based on that information, the vaccines protection against severe disease, hospitalization and death also could diminish in the months ahead.
How Long The Johnson & Johnson Vaccine Takes To Be Fully Protective Against Covid

The Johnson & Johnson COVID shot is one dose only. Youâre considered fully vaccinated two weeks, or 14 days, after your Johnson & Johnson vaccine, per the CDC, but your immune system continues to react to the shot for at least a month. Data from Johnson & Johnson published in the New England Journal of Medicine in January 2021 shows that the protectiveness of its vaccine against serious COVID also grows over time, becoming even more effective at 28 days post-shot â from 85% prevention of hospitalizations at 14 days to 100% prevention at 28 days. U.S. clinical trials revealed that for mild to moderate cases, the efficacy dropped a little, from 74.4% on Day 14 to 72% at 28 days.
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Is The Pfizer Booster The Same As The First Two Shots
Yes. According to Pfizer, its COVID-19 booster would be a third jab of the same vaccine you got with the first two doses.
Pfizer is working separately with its partner BioNTech on a version of the COVID-19 vaccine that targets the delta variant.
For more on coronavirus treatments and vaccines, here’s what we know about monoclonal antibody treatments, the new federal vaccine mandates and why some people may not want the shot.
The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.
Factors That Can Affect Immunity
There are different factors that can affect your immune response to a vaccine. Some examples include:
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Age: Very young children and older adults may have a decreased response to vaccines.
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Genetics: Your genes may influence how you respond to certain vaccines.
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Vaccine type: Some vaccines dont provide as much immunity as others, so booster shots may be needed.
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Health conditions: Certain conditions, like celiac disease and diabetes, may lower your response to vaccines.
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Being immunocompromised: People with a weakened or suppressed immune system may not develop strong immunity after vaccination.
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Are You Safe After Second Dose Of Vaccine
Both the Pfizer-BioNTech and Moderna COVID-19 vaccines introduce a part of the new coronavirus called the spike protein to your immunity system. The protein which is found on the virus surface is the one that helps the virus to bind and enter the host cells in the human body. The immune system has its own memory which uses the vaccine to understand and store the information about the spike protein. This helps your immunity system to protect you from the COVID-19 virus attack in the future.
A Mild Reaction To The Vaccine Is Just Your Immune System Working
Dr. Marks says a lot of people wonder what it means if they experience side effects, such as a fever or arm rash, and if that should prevent them from getting their second dose. These mild side effects are actually just your immune system responding. They are often more pronounced after the second dose. It means you have a vigorous immune system when you get those reactions, says Dr. Marks. If people didnt feel well at the first dose, they should be prepared for that possibility again and make sure they take some extra time if they need it. If you had an allergic reaction or a very severe reaction from the first dose, you should talk to your doctor, but otherwise people should get the second dose.
At the same time, people should not worry if they feel no effects after getting the vaccine. We know from the studies, some people also have no reaction to the vaccine, says Dr. Marks. So if you do not experience these mild reactions this is not a cause for concern either.
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How Long The Moderna Vaccine Takes To Be Fully Effective Against Covid
People who get the Moderna shot are on a slightly slower schedule than Pfizer vaccine, Quigley says: two shots, with four weeks between them. Like Pfizer, people with Moderna COVID vaccines will be considered fully protected 14 days post-second jab. According to the CDC study, Moderna and Pfizerâs vaccines are 90% protective against COVID two weeks after the second shot.
Phase Two And Three Clinical Trials Vaccine And Placebo
The efficacy of the Pfizer vaccine was tested in about 44,000 participants aged 16 years and over where COVID-19 was already circulating in communities. About half of these participants were randomised to receive the vaccine and the other half received a saline placebo.
The trial looked at how many people got COVID-19 symptoms after they were vaccinated compared to how many got COVID-19 after getting the placebo.
Participants had two doses of the vaccine or placebo, getting their second dose within 19 to 42 days after their first dose. They were then closely monitored and evaluated for at least 2 months after their second dose.
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Shall I Get My Booster
Yes – it may be the only shot at a normal Christmas.
You may be feeling confused about why you need to get yet another vaccine dose, if scientists said the first two worked so well.
There is a new Covid variant that has prompted a huge booster campaign.
Early indications are that this variant, called Omicron, may reduce the effectiveness of the vaccines, which were designed against the first Covid strain from Wuhan.
It means that in order to get the best protection against it, immunity levels need to be high.
Speaking of the importance of boosters, Deborah Dunn-Walters, professor of Immunology, University of Surrey & Chair of the British Society for Immunology COVID-19 and Immunology taskforce, said: Until the answers to these questions are known it is sensible to increase protective measures where we can.
Since we know that immunity does wane to some extent, and that boosters can increase immunity, then accelerating the booster program will protect more people.”
Risk Of Getting Covid

After the first vaccination, you may still get COVID-19 because your immunity to the virus is not yet fully developed. After the second vaccination, there is a much lower risk of becoming ill, because you are better protected. That is why it is important to get the second vaccination as well.
Information on how effective the vaccines are is provided on the page about COVID-19 vaccines. All vaccines prevent people from becoming ill due to the coronavirus. However, the vaccines work in different ways. See also the information provided on Government.nl.
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