January 12, 2022
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Antibodies are proteins made by the immune system in response to an infection or vaccination. They are present on the surface of important cells of your immune system called B cells. Other immune cells called T cells help clear the infection.
Antibody tests can detect the body’s levels of antibodies against a certain virus. When a test detects antibodies, it means that a person was previously infected or vaccinated for a disease such as COVID-19. Thus, antibodies are a signal that an individual is likely protected from future infection.
This article will explain what antibodies are, how they work, and how they differ when acquired from infection or vaccination.
HOW ANTIBODIES DEFEAT INFECTIONS
Antibodies play a key role in fighting certain types of infections. They work with other parts of your immune system to get rid of pathogens (bacteria or viruses that cause disease). That includes SARS-CoV-2, the virus that causes COVID-19.
However, it takes a while for this to work. If your immune system has never dealt with a particular virus before, it won’t have antibodies to the virus ready to go.
Antibodies attach very precisely to a specific spot on a given virus. So it takes your immune system a while to figure out which exact antibody will work to neutralize (counteract) a virus.
That’s one of the reasons it takes you a while to get better after you are infected with a new virus. Depending on the specific type of antibody, it can take a couple of weeks or so to produce the right antibodies in large enough amounts.
Even though antibodies are important for fighting and preventing many infections, not all antibodies the body produces against a virus are effective.
For example, different B cells in the body will produce multiple different antibodies that stick to different sites on the virus. But only attaching to some of these sites will actually inactivate the virus. So for a vaccine to work, it must produce this neutralizing antibody.
The body usually first produces a specific antibody type called IgM. Sometimes, doctors will test for IgM antibodies to see if you have recently been infected with a certain virus. For example, doctors commonly use this kind of test to check for recent infection with the hepatitis B virus.
A little later, the body produces other types of antibodies. An essential type is IgG antibodies. These tend to last longer than IgM antibodies. IgG antibodies are critical for controlling the initial disease and preventing re-infection if you are exposed again in the future.
HOW ANTIBODIES PREVENT INFECTIONS
After an infection, certain T cells and B cells that can recognize the virus stick around for a long time. Then, when they are re-exposed to the virus (or another pathogen), these special memory cells recognize it quickly and respond.
When this happens, you don’t get sick. Or, if you do get sick, you usually only get a very mild version of an illness. This is called protective immunity to a disease. Depending on the situation, this immunity might last for months or years.
You might also have partial immunity. This is like giving the immune system a head start that offers you some degree of protection, but not total protection.
Antibodies have a key role in treating infection and preventing disease. That’s why scientists have been so interested in understanding the role of antibodies in COVID-19.
The Food and Drug Administration (FDA) has granted Emergency Use Authorization (EUA) for some COVID-19 treatments. Some of the treatments include the use of plasma (the clear, liquid portion of blood) donated from people who have recovered from the illness.
The idea is that plasma contains antibodies to the virus that might help individuals recover more quickly from an infection.
Researchers are also hard at work developing cutting-edge synthetic (chemical) antibody therapies that might end up being an important part of treatment. Antibody products have already received EUA by the FDA. Some of these antibodies are used for prevention after exposure and early treatment in people who are high-risk for severe disease.
Studying how antibodies work in COVID-19 has also been critical for developing successful vaccines. This knowledge is also important for assessing how immunity to COVID-19 – either from infection or a vaccine – might decrease over time. This will help scientists determine when people might need booster vaccine shots to re-up their immunity.
ANTIBODIES FROM NATURAL INFECTION
When you develop antibodies through illness, your immune system reacts to protect you. First, it goes through a process of identifying the virus and eventually making effective antibodies.
Your B cells make antibodies to different parts of the virus. Some of the antibodies your body makes are effective, and some are not. These help you eliminate the virus and recover.
Hopefully, some of these antibodies also help protect you from future infections. For example, infection with COVID-19 seems to give you some protection from being re-infected, at least in the short term. However, it is still unknown how long that protection lasts.
Also, studies have indicated that people with symptoms of COVID-19 seem to produce effective, “neutralizing” antibodies. From experience with other viruses, scientists think it means that getting infected with COVID-19 probably leads to at least some level of protection against future infection.
Additionally, animal studies suggest at least some level of protective immunity, with at least some of this coming from antibody protection.
How long might natural immunity last?
How long protective immunity lasts after infection varies for different types of viruses.
Some viruses mutate (change) rather quickly. That means when you are exposed to a new strain of the virus, your previous antibodies might not work. This is why a new flu vaccine is created each year.
Immunity to some types of coronavirus may be short-lived. For example, people can get cold-like symptoms from certain coronaviruses season after season.
But coronaviruses don’t mutate as rapidly as viruses like the flu. This may mean that protective immunity could last longer for COVID-19 than it does for something like the flu.
Antibodies to COVID-19 do seem to decrease in the months after infection. However, that happens for all infectious diseases. Therefore, it doesn’t necessarily mean that immune protection is decreasing.
B cells may decrease their antibody production in the months after infection. But memory B cells can continue to circulate in the bloodstream for years. Presumably, these B cells could start releasing the neutralizing antibody if they were again exposed to the virus.
After they have studied a virus for a long time, scientists can determine whether a person is immune based on a blood test. For example, they might look for a certain concentration of a specific antibody.
Because COVID-19 is so new, scientists will have to see what immunity looks like over time. In one study, researchers found antibodies in the majority of people three months after experiencing symptoms from COVID-19.
How long immunity lasts might also be impacted by whether a person had an asymptomatic, mild, or severe infection.
Since people’s immune systems respond very differently to natural infection, it is difficult for scientists to pinpoint how long natural immunity to COVID-19 might last.
People’s immune systems respond more consistently to vaccination, which is why scientists recommend the COVID-19 vaccine even for people who have recovered from the virus.
ANTIBODIES FROM VACCINATION
Vaccination is a way for your body to build protective immunity without having to get sick first. Different types of vaccines do this in different ways.
Regardless of how a vaccine introduces your body to a virus, all vaccines essentially do the same thing:
The vaccination process prompts the body to make memory B cells, just like they do in natural infection. If you are ever exposed to the virus again, these B cells go into action right away and release antibodies that can target the virus.
These antibodies stop the virus before you get sick. Or, in some cases, you might get sick but with a much milder case. That’s because your immune system already has a head start—one it wouldn’t have had if you hadn’t been vaccinated.
Vaccine vs. natural immunity
There are a lot of similarities but also sometimes some differences between vaccine immunity and natural immunity. For example, in response to an infection or vaccination with a live virus, IgM antibodies usually are made first, followed by IgG and some other types of antibodies.
And just like in a natural infection, protective immunity doesn’t begin the moment you get vaccinated. It takes a couple of weeks or so for your immune system to form the antibodies and groups of B cells that it needs. That’s why you don’t get full protective coverage from a vaccination right away.
For the most part, the antibodies that you form from getting vaccinated are the same kind of antibodies you would get from a natural infection. One difference is that certain types of vaccines only show the immune system part of the relevant virus. Because of that, the immune system doesn’t form as many different types of antibodies as it would in the course of a natural infection.
However, this doesn’t mean that the antibodies formed are less effective than those formed in a natural infection. It’s just that someone who has been naturally infected might also have additional antibodies (many of which might be ineffective).
|Vaccine Immunity||Naturally Acquired Immunity|
|Protective immunity that builds over timeBody may be introduced to one specific antibody that has been found effective in fighting the virusThe specific antibody acquired through vaccination is effective at fighting the virusVaccines provide immunity without the risk of complications from exposure to a virus||Protective immunity that builds over timeBody may form many different antibodies in response to an illness The specific antibody acquired through infection is effective at fighting the virusNatural immunity comes with the risk of complications from exposure to a virus|
To make a vaccine, researchers carefully select a specific part of the virus shown in lab studies to trigger an antibody response that effectively neutralizes the virus.
Most of the vaccines for COVID-19 only show the immune system part of the virus. This is a protein chosen to trigger a strong immune response. (This includes the Pfizer and Moderna mRNA vaccines.) So, someone who had naturally been infected with the virus might have some additional antibody types not found in someone who had been successfully vaccinated.
The difference between vaccine-acquired and naturally acquired immunity is a very complex topic. You can’t just compare natural infection to vaccination because not every vaccine has the same properties. In addition, not every vaccine will trigger the same immune response.
In some cases, a specific vaccine might not provide as effective an antibody response as being naturally infected. But other times, the reverse might be the case. This is especially true if a vaccine has been designed to provoke a strong response.
POTENTIAL RISKS OF ANTIBODIES
Antibodies provide many benefits. They eliminate infections and provide protective immunity against future infections.
However, in rare circumstances, antibodies might actually worsen an infection. For example, antibodies might bind to a virus in such a way that makes it easier to enter cells.
This might mean that if a person is re-infected after an initial mild infection, they could then have a more severe case the second time. Or, it theoretically might mean that a person could have a worse response to potential infection if they have previously been vaccinated for the disease.
This scenario has been called “antibody-dependent enhancement.” It has been found in viruses such as dengue. In that virus, it complicated the creation of successful vaccines.
Because researchers were aware of this theoretical possibility, they have been looking very carefully to see whether this might be possible in COVID-19. However, no signs of antibody-dependent enhancement have been found in COVID-19.
Antibodies help your body fight off certain infections. They work when your body is actively ill. They also stick around to help prevent you from becoming re-infected.
Vaccines are another way your body can acquire antibodies. Vaccines introduce your body to one or more proteins from a virus. This prompts it to make B cells, which produce antibodies against a specific virus.
Vaccines are a safe and effective way to protect yourself from infectious diseases. COVID-19 vaccines are the safest way to protect yourself from COVID-19. They are widely available to everyone 12 and older. Vaccine data as of August 2021 shows that the odds of being reinfected with COVID-19 are 2.34 times greater for those who are unvaccinated than those who have received COVID-19 vaccination.
Source: Very Well Health
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Theo tuổi tác, hệ miễn dịch của chúng ta trở nên kém hiệu quả hơn trong việc đối phó với các tình trạng nhiễm trùng cũng như kém đáp ứng với việc chủng ngừa. Đồng thời, hệ miễn dịch lão hóa có mối liên hệ với tình trạng viêm mạn tính, từ đó làm tăng
With age, the human immune system becomes less effective at tackling infections and less responsive to vaccinations. At the same time, the aging immune system is associated with chronic inflammation, which increases the risk of almost all conditions linked to old age. The good news is that exercising and adopting the right diet may help