Six Questions About Waning Immunity to Covid-19 Answered

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A booster shot is administered in New York. A shot like this can help spur a person's immune system to fight Covid-19. Steve Pfost is from Newsday.

When Pfizer, Moderna and Johnson & Johnson announced their Phase 3 clinical trial results, experts cheered. The walls of the vaccines seemed to be nearly impenetrable against the disease. The FDA and CDC recommend a shot to boost immunity for all adults six to eight months after their second shot of Pfizer or Moderna's vaccine, or two months after the first shot of Johnson & Johnson.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases told the New York Times that more and more people are getting breakthrough infections, and that more and more people are winding up with infections.

Waning immunity isn't as scary as it sounds. Most people still get a high level of protection against severe disease from the vaccines. Mark Slifka is an immunologist at Oregon Health and Science University. That is a misconception. 90 percent protection against mortality and hospitalization is still provided by vaccines. Infections are still three times more likely in unvaccinated individuals. Only a small percentage of infections have led to hospitalization in vaccine patients compared to unvaccinated patients.

There are new variant that play a role in waning immunity. Scientists don't yet know if the Omicron variant has the ability to sneak past our immune system.

We reached out to the experts to learn more about waning immunity and how to protect it.

1. When you get the vaccine, what happens?

Your immune system is made up of three main soldiers that work together to stop infections from wreaking havoc on your body.

Since the beginning of the Pandemic, we have been hearing a lot about the antibodies. The most important component of immunity is the proteins and they have been used in both testing and treatment for COVID-19. They are created by B cells.

Vaccination causes B cells to make specific SARS-CoV-2-specific antibodies that attach to different parts of the virus. Your best defense is neutralizing antibodies. They cling to the spikeProtein on the outside of the virus which stops it from entering your cells.

Antibodies are great. Kennedy says that they take care of a lot of viruses. Once the virus gets inside a cell, the immune system can't do anything about it. That's where your T cells come in.

T cells find and kill their own cells after they have been exposed to the virus, so it can't spread. The T cells are important for ending an infection, but not great in preventing one, according to a researcher at the La Jolla Institute for Immunology. You will have less severe disease if you have a good T cell response.

2. What does waning immunity look like?

Your body builds up its immune army after an injury or vaccine, in case the invader is still present. Your B cells are secreting their anti-viruses for a while. When they don't come in contact with the enemy for an extended period of time, the production of cells and proteins slows down, and your immunity starts to diminish. The B cells and the T cells are used to fight an infectious disease, and the bullets that are shot by B cells are used by soldiers. It doesn't make sense for the immune system to continue to fire bullets if the invader is gone.
A small percentage of B and T cells can live for months, years and sometimes even decades after your antibody levels fall. If the virus comes back, these cells can ramp up your immune response. If they don't see the virus again, even they will die and your immunity will decline further.

Depending on what virus the cells are trained to kill, how long the cells stick around depends. The vaccine can give you many years of protection. The flu vaccine can give you a couple months of protection, but most of the time it's useless. The Pertussis vaccine is one of the vaccines that has a booster recommended by the CDC after a few years of protection. Scientists don't know how long the memory B and T cells stick around after a few months.

3. What does waning immunity look like?

After your second jab of Pfizer or Moderna or two months after your first of Johnson & Johnson, scientists have found your likelihood of getting a breakthrough infection rises, though you are still mostly protected from severe disease and death. This is the beginning of immunity waning.

Rosemary Rochford is an immunologist at the University of Colorado Anschultz School of Medicine. We don't see a lot of breakthrough disease. Those with breakthrough infections are less likely to end up in the hospital than unvaccinated people.

Kennedy says that immunity is not an on-off switch. It is a spectrum. If you have a high level of antibodies, they will destroy the virus before it can cause any symptoms. The disease will be relatively short and mild if your immune system doesn't produce as many antibodies. If you have little or no immunity left, you will be at risk of getting sick from the virus.

Initially, we saw a decline in antibodies, but they were still high. Protection against severe disease is also waning.

4. Is it possible to tell if I need a booster shot?

Not yet. There are two reasons for this. Scientists don't know the exact level of antibodies you need to be protected from. They would need to have access to blood samples from a vaccine-vaccinated population before an outbreak. They can compare the number of antibodies in a blood sample to who got sick and how sick, assuming that their exposure to disease was the same.

It took some luck to discover this threshold for other diseases. Slifka says that finding this number for measles was a convenient accident. A blood drive at Boston University led to an outbreak of the disease. Researchers could compare the level of antibodies leftover from vaccination in each sample with who got sick and who didn't, and find the level at which individuals lost protection.

The reason scientists don't know is because they don't know how much of the story is true. T cells can take over in their absence. You don't need any of the other immune functions if you have a lot of antibodies. Kennedy says you don't need any T cells. If you have a lot of T cells, then the T cells can compensate if you don't have a lot of antibodies. If you had a low level of antibodies, you could still be protected.

5. What role do new variants play?

It is possible that the changes allow the virus to evade our immune system. The previous year's vaccine doesn't provide enough protection the next year because the virus is so rapid.

Delta and Omicron are two new strains of the disease that have a spikeprotein that may help them avoid detection of antibodies.

The Delta variant is more infectious than previous versions, meaning that a person with this strain usually carries more viruses than someone with another strain. In some cases it can overwhelm the immune system with a lot of numbers. If you have a piece of cake with 100 antibodies, you can wrap up the one virus that is in your body. Says Rochford. It takes a little bit longer for the antibodies to overcome the virus, if you have 1000 viruses get in, and you have 100.

Scientists are looking at how the vaccines fare against Omicron. It is not known if the spike protein can help it evade immunity or affect the severity of the disease.

Since a booster shot increases your level of antibodies, it can help protect against the Delta variant. After the second shot of the Pfizer vaccine, the scientists found that people's blood samples were able to neutralize more strains of the virus. The booster dose increases the magnitude of the response, but also increases the breadth of different variant that aren't even in the formula.

T cells formed after an infection or vaccine mount robust immune responses against the Delta variant, according to a September 2021 correspondence in Nature. If the T cells are still there, it's likely that they will still be able to prevent severe disease, according to Sette.

6. I don't know when I should get my third shot.

The CDC and FDA have had to identify the time that seems to make the most sense for most people because immunity fades at different rates. You don't want to tell people you have to get a booster. Kennedy says that it would provide a lot of protection, but now you are over-vaccinating people. The recommended time for breakthrough infections is six to eight months after two doses of Pfizer or Moderna. Kennedy suggests that if you have a compromised immune system, you should consider getting a third shot earlier, but for most people, anywhere in the six- to eight-month range would be practical. The first Johnson and Johnson vaccine should be followed by a second shot.

Kennedy says that you should consider your risk of exposure when you consider the rate at which your immunity fades. What will you be doing over the next few months? If your plans include traveling or large gatherings, you might want to get your booster shot sooner rather than later.

The answer to when to get a booster is simple. She says when you can.

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