Tthe growing prevalence of new variants of coronavirus raises questions about protecting people who have already received their COVID-19 shots from evolving forms of the SARS-CoV-2 virus. Here, specialist in microbiology and infectious diseases William Petri of the University of Virginia answers some frequently asked questions about COVID-19 booster shots.
1. What is a booster shot?
Boosters are an additional dose of a vaccine given to maintain vaccine-induced protection against a disease. They are commonly used to boost many vaccines because immunity can wear out over time. For example, the file flu vaccine needs reinforcement every year and diphtheria and tetanus vaccine every 10 years.
The promoters are usually identical to the original vaccine. However, in some cases, the booster shot has been modified to improve protection against new viral variants. He seasonal flu vaccine, above all, it requires annual reinforcement because the flu virus changes so quickly.
2. Do I need a COVID-19 booster?
Not yet. In early July 2021, none of the U.S. government authorities recommended a booster. This includes the Centers for Disease Control and Prevention, the Food and Drug Administration, and the Advisory Committee on Immunization Practices at the CDC.
3. Why is reinforcement not recommended yet?
Although vaccine-induced immunity may not last forever, it is unclear when reinforcement will be needed.
Encouragingly, all currently authorized COVID-19 vaccines induce robust immune memory against coronavirus. The vaccine teaches the immune system memory B cells to produce antibodies when you are exposed to the virus. Researchers have detected high levels of memory B cells in the lymph nodes of people who received the Pfizer vaccine at least 12 weeks after getting the shot.
Studies also suggest that authorized COVID-19 vaccines continue to offer protection even against emerging strains of coronavirus. Among study participants, he had the Johnson & Johnson vaccine 73% and 82% efficiency 14 days and 28 days after firing, respectively, to prevent severe beta variant disease. And a preliminary study that has not been reviewed by experts found that the Pfizer vaccine was 88% effective against the delta variant.
The other source of long-lasting antibody responses against coronavirus are the so-called cells plasmablasts residing in the bone marrow. These cells continuously produce antibodies and do not require reinforcement to maintain their activity. Fortunately, plasmablasts have been detected in the bone marrow of people who received the COVID-19 vaccine up to 11 months, indicating a certain degree of long-lasting immune memory.
4. How will I know if I need reinforcement?
You may have to wait for an outbreak in vaccinated people. Researchers continue to discover the best way to measure the strength of someone’s vaccine-induced immunity. COVID-19 vaccines have been so effective that there are not many flaws to try.
The best candidate to measure are certain antibodies that the vaccine induces the immune system to produce. They recognize the ear protein which allows the coronavirus to enter and infect cells. Evidence supporting the importance of anti-ear antibodies includes a study showing that slightly more effective mRNA vaccines such as Pfizer and Moderna generate higher levels of antibodies in the blood than adenovirus vector vaccines such as Johnson & Johnson and AstraZeneca. In a preliminary study which has not yet been peer-reviewed, peak antibody levels were lower in people who captured COVID-19 after being vaccinated with the Oxford-AstraZeneca vaccine.
Medical workers would love to be able to do a blood test to tell patients how well they are protected or not from COVID-19. This would be a clear indication of whether a booster shot is needed.
But until researchers know for sure how vaccine-induced immunity is measured, the next indication that boosters may be needed are advanced infections in older adults who have already been vaccinated. People over the age of 80 manufacture lower levels of antibodies after vaccination, so that their immunity may decrease before that of the general population. It is also likely that the elderly are the more susceptible to new viral variants which avoid the protection offered by current vaccines.
5. I am immunocompromised: should I worry?
Reinforcement may be needed for immunocompromised people. In one study, 39 of 40 kidney transplant recipients and a third of dialysis patients has not been able to produce antibodies after vaccination. Another study identified 20 patients with rheumatic or musculoskeletal diseases on drugs that suppress the immune system that also had no detectable antibodies. Both studies were done after patients received the full dose of vaccine.
Drivers have been shown to help in these cases. In one study, a third of patients with solid organ transplantation who had a suboptimal response to two doses of Pfizer or Moderna vaccines were able to develop an antibody response with a third dose.
Those who are immunocompromised may wonder if the vaccine they have received is successfully generating immunity in their body. A preliminary study that has not yet been reviewed by experts found that in test aimed specifically at anti-ear antibodies the trigger for the vaccines may be helpful in determining if the vaccine was working. But for now, the The FDA does not recommend it antibody tests to assess immunity.
6. Does my reinforcement have to match my first shots?
Probably not. Recent research has shown that mRNA vaccines, such as Pfizer and Moderna, can be mixed with adenovirus-based vaccines such as AstraZeneca with comparable results.