Immune system research helps answer questions about the COVID-19 vaccineExBulletin

Mary Louise Kelly, Host:

As the COVID-19 vaccine is deployed, three major questions remain. First, can vaccinated people still spread the disease? Second, does the vaccine remain effective as the virus evolves? And third, how long does the vaccine last? Richard Harris of NPR says immunologists are working hard to get answers.

Richard Harris, Signature Line: Let’s start with the first question as to whether vaccinated people can still spread the disease. Marion Pepper, an immunologist at the University of Washington, says this is an open question about the vaccine in general, not just this vaccine.

Marion Pepper: It’s hard to say because we’re constantly attacked by a variety of pathogens and we don’t know when the immune system is responding.

Harris: We never know about them because we may have infections that don’t get sick, but we may be spreading the disease. Howard Hughes researcher at Rockefeller University, Michel Nussenzwei, says your immune system may not be able to completely prevent the virus from starting to multiply in you after infection.

MICHEL NUSSENZWEI: Spreading it is actually a function of the amount of virus you are producing.

Harris: If your immune system starts up fast enough, you can prevent the virus from starting to multiply.

NUSSENZWEI: It’s a bit of a race between the immune system and the virus.

Harris: Vaccines are likely to prevent the spread of large numbers of viruses, but scientists are still trying to figure them out. It is difficult to answer the second question as to whether the vaccine will remain effective as the virus evolves. Scientists are not worried about the current mutation. And in the long run, Pepper says there are ways to adapt to your immune system.

PEPPER: Everyone is clearly worried about the evolution of the virus, but the responsiveness of memory B cells also evolves over time.

Harris: Memory B cells remember the infection and help the immune system produce antibodies. And they don’t just remember the viruses they encountered. Surprisingly, they can produce randomly changing antibodies, which help protect against new virus strains.

Pepper: Mature cells deliberately introduce mutations into DNA at almost the only time in the body.

Harris: Obviously, there are viruses that can circumvent this clever system. Therefore, a new flu shot is required every year. For COVID, you have to wait. Finally, the question is how long the vaccine will last. Stephen Jameson of the University of Minnesota School of Medicine states that in some cases, the memory of the immune system can be very long.

STEPHEN JAMESON: A type of natural infectious disease that can immunize you for a lifetime. You only get it once. You are protected for the rest of your life.

Harris: Vaccines mimic natural infections and provoke an immune response, but boost immunity may be needed to maintain immunity. It depends on the nature of the infection. For people with COVID-19, there is already evidence that immunity lasts for months, but beyond that there are open issues.

Jameson: The good thing is that if you find that your immune response has diminished somewhat, you may need another booster, like many other vaccines. Maybe you get another booster after a year or something.

Harris: These questions reflect how scientists have come to understand our immune system in recent years. Marion Pepper also says that COVID reveals that we still don’t know how the immune system protects us from viruses.

Pepper: It’s really interesting to see this unfold in real time. Because we are learning a lot about this virus and its immune response in unprecedented ways.

Harris: I asked Michel Nussenzwei another big picture question.

Will we be saved by the immune system?

NUSSENZWEI: Yes, I’m sure.

Harris: Richard Harris, NPR News.

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