In an attempt to ensure the effectiveness of their COVID-19 vaccines against new variants of the new coronavirus, Pfizer and Moderna are testing a third booster injection of their respective two-dose vaccines.
On February 25, Pfizer announced that it is studying a third booster dose in some people who received the first dose of the vaccine more than six months ago. The company specifically stated that the emerging and future variants of SARS-CoV-2, the coronavirus that causes COVID-19, were the reason for the study. Pfizer also said it is exploring the possibility of a new “variant-specific vaccine” that would target B.1.351 (the highly infectious South African variant).
Moderna also announced that it has finished manufacturing a specific vaccine for a variant for target B.1.351, and the company is ready to start a Phase 1 clinical trial of the vaccine. Moderna says it will explore the use of the new vaccine as a “booster dose” for people who are already vaccinated. This booster injection will be analyzed in a Phase 1 clinical trial to see if it can “increase immunity against the worrying variants,” noted Moderna.
Both companies have hinted that it will take months for preliminary data to be available. In the meantime, you are likely to have doubts about the potential booster doses of COVID-19. Here’s what the experts know so far.
How do COVID-19 mRNA vaccines work?
The Pfizer and Moderna vaccines use a new type of technology called messenger RNA (mRNA). The vaccines, which do not contain live viruses, encode a part of the spike protein – the part of the virus that binds to human cells – found on the surface of SARS-CoV-2, according to the Centers for Disease Control and Prevention (CDC) ).
The mRNA gives cells instructions to develop a piece of that protein that is unique to SARS-CoV-2. His immune system recognizes these new pieces of protein as foreign invaders and assembles an immune response to fight what he interprets as an infection (even if there is no threat). This causes you to develop specific antibodies to SARs-CoV-2, which will help you fight future infections.
Your body eventually eliminates mRNA and proteins, but the antibodies remain there. How long they last, however, is still being studied – the CDC specifically says that more data is needed for both vaccines.
How effective are Pfizer and Moderna vaccines?
Both vaccines were found to be highly effective during Phase 3 clinical trials. Pfizer’s Phase 3 clinical trial research showed that their vaccine is 52% effective after the first dose and about 95% effective after the second dose in adults with 16 years or older.
Results of the Phase 3 clinical trial of Moderna, which were published in The new English medical journal, found that the company’s vaccine is about 94.1% effective against COVID-19 in people aged 18 and over
But – and this is a big but – the tests were conducted before variants like B.1.1.7, which was first detected in the UK, and B.1.351 started to spread quickly, says William Schaffner, MD, an infectious disease specialist and professor at the Vanderbilt University School of Medicine. In other words, there is a possibility that the effectiveness of vaccines today is less than what data from months ago indicate.
With the new research being conducted, both Pfizer and Moderna are “trying to preventively assess whether variants may impact the immunity generated by their vaccines,” says Reynold Panettieri, MD, director of the Institute of Medicine and Translational Science at Rutgers University.
Is a third booster dose needed to protect COVID-19?
Both companies suggested that they are concerned about the potential impact of the South African variant on the effectiveness of their vaccines, as well as the possibility that future variants will make their vaccines less effective.
“It’s still the beginning of science,” says Dr. Schaffner. “We may be able to use the standard vaccine as a backup to protect against variants – if we need to. We still don’t know how long the standard two-dose vaccine will protect us. ”
There are different strategies for dealing with the variants, adds infectious disease specialist Amesh A. Adalja, MD, a senior fellow at the Johns Hopkins Center for Health Security. “One is to reformulate the vaccine and the other to add another booster with the same formulation”, he explains. Creating a booster can raise antibodies and T cells (a type of white blood cell that is an essential part of your immune system) enough to help fight variants of the original dominant SARS-CoV-2 strain.
It is also possible that a booster injection will make an already effective vaccine even more effective. “They may be trying to see if they can increase effectiveness to closer to 100%,” says Dr. Panettieri.
Until specialist doctors know more, Dr. Adalja emphasizes that receiving two doses of the Pfizer or Moderna vaccine will still offer valid protection. “The priority should still be to vaccinate people with the original vaccine, which has an impact on all variants when it comes to what matters – serious illness, hospitalization and death,” he says.
In addition, people across the country are still waiting to receive their first dose of the vaccine. “[A third dose] it would be logistically difficult in the short term ”, says Dr. Adalja. But, he adds, distribution should become easier over time, as more vaccination systems and supplies become available.
This article is correct at the time of publication. However, as the COVID-19 pandemic evolves rapidly and the scientific community’s understanding of the new coronavirus develops, some of the information may have changed since the last update. While our goal is to keep all of our stories up to date, visit the online resources provided by CDC, WHOit’s yours local department of public health to stay informed about the latest news. Always speak to your doctor for professional medical advice.
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