It is important to remember that some people with antibodies to SARS-CoV-2 may become infected after vaccination (vaccine breakthrough infection) or after recovering from a past infection (reinfected).
At this time, it is unknown for how long antibodies persist following infection and if the presence of antibodies confers protective immunity.
Reinfections can and have happened even shortly after recovery, the researchers said. And they will become increasingly common as immunity wanes and new SARS-CoV-2 variants arise.
Although the immune correlates of protection are not fully understood, evidence indicates that antibody development following infection likely confers some degree of immunity from subsequent infection for at least 6 months.
How Strong Is Immunity After a COVID-19 Infection? About 90% of people develop some number of protective antibodies after a COVID-19 infection, according to the CDC. But how high those levels climb appears to be all over the map.
After you recover from a virus, your immune system retains a memory of it. That means that if you get infected again, proteins and immune cells in your body can recognize and kill the virus, protecting you from the disease and reducing its severity.
If I already had COVID-19 and recovered, do I still need to get a COVID-19 vaccine? You should get a COVID-19 vaccine even if you already had COVID-19. Getting a COVID-19 vaccine after you recover from COVID-19 infection provides added protection to your immune system.
It takes a couple of weeks for your body to build immunity after vaccination.
"People who have not knowingly been infected with COVID should be vaccinated, and after that, be assured that they are protected against serious disease from this virus,"
Data released by the U.S. Food and Drug Administration (FDA) show that COVID-19 protection from the Pfizer/BioNTech vaccine was demonstrated in the clinical trials at about 14 days after the first shot. The FDA said some level of immunity may start sooner, but how much is not certain.
The bottom line It's possible to get sick with more than one COVID-19 variant at the same time. But it's not clear if dual infection is more serious than being sick with only one variant.
Here's what we know from studies of prior variants, including Delta: On average, people can begin spreading the virus 2-3 days before their symptoms begin, but infectiousness peaks 1 day before their symptoms begin. On average, people can continue to spread the virus another 8 days after their symptoms began.
A UCLA study shows that in people with mild cases of COVID-19, antibodies against SARS-CoV-2 — the virus that causes the disease — drop sharply over the first three months after infection, decreasing by roughly half every 36 days. If sustained at that rate, the antibodies would disappear within about a year.
A COVID-19 vaccination may also cause a positive antibody test result for some but not all antibody tests. You should not interpret the results of your SARS-CoV-2 antibody test as an indication of a specific level of immunity or protection from SARS-CoV-2 infection.
Fortunately, there's no reason to be worried. Just because you didn't have a reaction – or not much of one – doesn't mean your body isn't mounting a response to the vaccine. The reality is that not everyone has a reaction. As a matter of fact, studies show only about 50% of patients experience side effects.
If you had COVID-19 before being vaccinated, the first injection may cause more noticeable side effects than for people who have not had the coronavirus. If you have never had COVID-19, you may notice more side effects after the second dose than after the first dose.
• COVID-19 vaccines are safe and effective.
• Millions of people in the United States have received COVID-19 vaccines under the most intense safety monitoring in U.S. history.
• CDC recommends you get a COVID-19 vaccine as soon as possible.
Vaccines work by stimulating your immune system to produce antibodies, exactly like it would if you were exposed to the disease. After getting vaccinated, you develop immunity to that disease, without having to get the disease first.
Because vaccines are not 100% effective, as the number of people who are fully vaccinated goes up, the number of vaccine breakthrough infections will also increase. However, the risk of infection remains much higher for unvaccinated than vaccinated people.
Symptoms. People with post-COVID conditions (or long COVID) may experience many symptoms. People with post-COVID conditions can have a wide range of symptoms that can last more than four weeks or even months after infection. Sometimes the symptoms can even go away or come back again.
When SARS-CoV-2, the virus causing COVID-19, enters the body, its spike protein binds with the ACE2 receptor, gaining entry to the cell. The immune system responds by producing protective antibodies that bind to the invading virus, blocking or neutralizing its effects.
When a person gets a viral or bacterial infection, a healthy immune system makes antibodies against one or more components of the virus or bacterium.
The COVID-19 coronavirus contains ribonucleic acid (RNA) surrounded by a protective layer, which has spike proteins on the outer surface that can latch on to certain human cells. Once inside the cells, the viral RNA starts to replicate and also turns on the production of proteins, both of which allow the virus to infect more cells and spread throughout the body, especially to the lungs.
While the immune system could potentially respond to different parts of the virus, it's the spike proteins that get the most attention. Immune cells recognize the spike proteins as a foreign substance and begin producing antibodies in response.
After infection with the COVID-19 virus, it can take two to three weeks to develop enough antibodies to be detected in an antibody test, so it's important that you're not tested too soon.
Antibodies may be detected in your blood for several months or more after you recover from COVID-19.
Advancing public health But even a mild SARS-CoV-2 infection can cause long COVID. And with the high transmissibility of the Omicron variant—which often results in milder disease outcomes—many patients may be concerned about developing long COVID.
“The first is the severity of the coronavirus infection itself — whether the person has a mild case, or a severe one,” Galiatsatos says. Milder cases are less likely to cause lasting scars in the lung tissue.