Pfizer and Moderna are testing a third ‘booster’ dose for their COVID-19 vaccines

Photo Credit: Andriy Onufriyenko - Getty Images

Photo Credit: Andriy Onufriyenko – Getty Images


In an attempt to ensure the effectiveness of their COVID-19 vaccines against new variants of the novel coronavirus, both Pfizer and Moderna are testing a third booster shot of their respective two-dose vaccines.

On February 25, Pfizer announced that it is studying a third booster dose in some people who received their first dose of the vaccine more than six months ago. The company specifically stated that 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 “specific variant vaccine” that targets B.1.351 (the highly infectious South African variant).

Moderna also announced that it has finished manufacturing a specific variant vaccine to target B.1.351, and the company is set to begin a phase 1 clinical trial of the vaccine. Moderna says she will explore using the new vaccine as a “booster dose” for people who are already vaccinated. This booster vaccine will be tested in a phase 1 clinical trial to see if it can “boost immunity against the variants of interest,” Moderna noted.

Both companies hinted that it will be months before even preliminary data is available. In the meantime, you probably have questions about possible COVID-19 booster shots. This is what the experts know so far.

How do COVID-19 mRNA vaccines work?

Both the Pfizer and Moderna vaccines use a newer 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 attaches to human cells, found on the surface of SARS-CoV-2, according to the Centers for Control and Disease Prevention (CENTERS FOR DISEASE CONTROL AND PREVENTION).

The mRNA gives your cells instructions to make a part of that protein that is unique to SARS-CoV-2. Your immune system recognizes these new protein fragments as foreign invaders and generates an immune response to fight what it interprets as an infection (even if there is no threat). This causes you to develop specific antibodies against SARs-CoV-2, which will help you fight future infections.

Your body eventually removes both the mRNA and the proteins, but the antibodies stick around. However, how long they last is still being studied; the CDC specifically says that more data is needed on both vaccines.

How effective are the 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 approximately 95% effective after the second dose in adults 16 years of age and older.

Results of Moderna’s Phase 3 clinical trial, which were published in The New England Journal of Medicine, found the company’s vaccine to be approximately 94.1% effective against COVID-19 in people 18 years of age and older

But, and this is a big but, the rehearsals were carried out prior to Variants like B.1.1.7, which was first detected in the UK, and B.1.351 began to spread rapidly, says William Schaffner, MD, infectious disease specialist and professor at Vanderbilt University School of Medicine. . In other words, there is a possibility that the effectiveness of vaccines today is less than what the data from months ago indicates.

With the new research underway, both Pfizer and Moderna are “trying to preemptively address whether the variants could affect the immunity generated by their vaccines,” says Reynold Panettieri, MD, director of the Institute for Translational Science and Medicine at the University of Rutgers.

Is a third booster dose needed for protection from 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 could make their vaccines less effective.

“It’s still early in the science,” says Dr. Schaffner. “It is very possible that we can use the standard vaccine as a booster to protect against variants, if we need it. 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 expert Amesh A. Adalja, MD, a principal investigator at the Johns Hopkins Center for Health Safety. “One is to reformulate the vaccine and the other is to add another booster with the same formulation,” he explains. Creating a booster could boost 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 parent, dominant strain of SARS-CoV-2. .

It’s also possible that a booster shot could make an already effective vaccine even more effective. “They may be trying to see if they can get the efficacy close to 100%,” says Dr. Panettieri.

Until medical experts know more, Dr. Adalja emphasizes that receiving two doses of the Pfizer or Moderna vaccine will still offer dignified protection. “The priority must remain to vaccinate people with the original vaccine, which impacts all variants when it comes to what matters: severe illness, hospitalization and death,” he says.

Also, 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 accurate as of press time. However, as the COVID-19 pandemic rapidly evolves and the scientific community’s understanding of the novel coronavirus develops, some of the information may have changed since it was last updated. While we aim to keep all of our stories up to date, please visit the online resources provided by Centers for Disease Control and Prevention, WHO, and you local public health department to stay informed on the latest news. Always talk to your doctor for professional medical advice.

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