- The coronavirus has already gone through many mutations and will continue to evolve over time.
- Growing evidence suggests the vaccines will provide long lasting immunity, even against new variants.
- But experts are watching the variants closely to see whether a booster shot will be needed to end the pandemic.
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As coronavirus variants emerge and spread, speculation is increasing about whether we’ll eventually need booster shots to maintain our protection against COVID-19.
All viruses mutate. The coronavirus that causes COVID-19, SARS-CoV-2, has already gone through many mutations and will continue to evolve over time.
But that doesn’t necessarily mean our vaccines will lose their power to protect us, or that we’ll need a booster shot.
Our immune system is complex and robust, so even when the coronavirus mutates, our cells — which are skilled at remembering pathogens — will still be able to recognize the virus and get to work.
Due to the complex nature of our immune system, many infectious disease specialists don’t expect booster shots to be necessary — at least anytime soon.
Emerging evidence suggests the vaccines will provide long lasting protection and hold up against the current variants.
The Centers for Disease Control and Prevention (CDC) also recently stated there’s no data to suggest we’ll need COVID-19 vaccine boosters — but that scientists will continue to monitor the virus to see if this changes over time.
This week Pfizer and BioNTech said that they will seek an emergency use authorization (EUA) for another booster shot from the U.S. Food and Drug Administration, according to Reuters. The pharma companies will ask that a booster shot be allowed under emergency circumstances due to a greater risk of infection about 6 months after the vaccine and due to the rise of new, more infectious variants.
Growing evidence suggests the shots will provide long lasting immunity, even against new variants.
In addition to antibodies that act fast and attack the coronavirus spike protein, our bodies have the cell-mediated immune response, which includes T cells and memory B cells.
“Vaccines induce much more than antibodies. T-cell immunity is a critical component of immunity that the press often ignores when reporting on vaccination studies,” Dr. Amesh Adalja, an infectious disease specialist and a senior scholar at the Johns Hopkins University Center for Health Security, told Healthline.
Both T cells and memory B cells hide in our lymph nodes and jump into action if they detect a pathogen in the future.
T cells are crucial for long lasting immunity and protection against severe disease.
All the major vaccine clinical trials looked at T-cell production and concluded that the shots produce a strong and durable T-cell response, according to Dr. Monica Gandhi, an infectious disease specialist with the University of California, San Francisco.
Multiple studies have found that those T cells, which target several parts of SARS-CoV-2, hold up over time.
Memory B cells are also generated “and would be expected to spring into action upon reexposure and generate antibodies long after vaccination,” Adalja said.
Memory B cells are a type of B cell that the immune system produces in response to exposure to an antigen. They persist in the body (in lymph tissue, organs, bone marrow, and in circulation) for months to years, depending on the specific antigen they were produced in response to.
A paper published last month found that B cells are able to produce new antibodies that specifically target a variant if a person with immunity is exposed to a new variant.
Memory B cells “aren’t going to produce antibodies against some old ancestral strain, they’re going to produce antibodies against what they see,” Gandhi said.
Scientists have yet to discover just how long protection from our T cells and memory B cells will last, but research on other viruses show they can, in certain cases, last for years.
With measles, for example, T cells have been detected up to 34 years after vaccination.
As of now, it doesn’t look like people who originally got vaccinated with the one-dose Johnson & Johnson shot will need a booster shot of one of the messenger RNA (mRNA) vaccines like Pfizer-BioNTech or Moderna.
According to Gandhi, there’s currently no evidence there are more breakthrough infections in people who have received the J&J shot than people who’ve gotten one of the mRNA vaccines.
The J&J shot works similarly to the mRNA vaccines. It uses DNA “to produce mRNA, and then it looks exactly like an mRNA vaccine. It’s not that different,” Gandhi said.
Gandhi said antibodies always peter out after vaccination, and if scientists were to only measure antibodies when evaluating the durability of immunity, they would always recommend booster shots.
Antibody levels aren’t our only clue as to how immunity persists. T cells and memory B cells step up to fight, too.
According to Adalja, people who are immunocompromised who did not produce strong immune responses after vaccination may benefit from a booster shot.
“There may be a need for boosters in immunosuppressed population in a shorter time interval, but I do not think short-term boosters will be needed for the general population,” Adalja said.
Scientists will need to continue studying how vaccinated people’s immune responses — including both those in the general population along with people who are immunocompromised — behave over time.
If more and more vaccinated people begin to experience breakthrough infections that are severe, we may need another dose to boost antibodies against new variants.
“To me, the threshold for booster vaccines is when fully vaccinated individuals are getting hospitalized with breakthrough infections, and that is not something that is occurring outside of rare occurrences,” Adalja said.
As new variants emerge and spread, speculation is increasing regarding whether we’ll eventually need booster shots to maintain our protection against COVID-19.
But many infectious disease specialists say vaccine-induced immunity against severe COVID-19 appears to be strong and long lasting, suggesting we probably won’t need a booster shot anytime soon.
Scientists will continue observing people over time to understand how long protection against severe disease lasts.