The Johnson & Johnson vaccine requires only a single dose.
The US Food and Drug Administration (FDA) this week approved the use of the COVID-19 vaccine in adults developed at Johnson & Johnson Laboratories.
The main feature of this vaccine is that, unlike the others that are already used, it works with a single dose.
Maureen Ferran, a virologist at the University of Rochester, explains how this vaccine works, the third one approved by the FDA and how it differs from those produced by Pfizer-BioNTech and Moderna.
1. How does the Johnson & Johnson vaccine work?
It is a viral vector vaccine.
To create it, the Johnson & Johnson team took a harmless adenovirus – the viral vector – and replaced a small part of its genetic component with genes for spike proteins (the outer parts of the virus that look like a crown) from SARS-CoV.2 , the virus that produces covid-19.
Then this adenovirus modified It is injected into the patient’s arm and enters his cells.
The cells then read the genetic instructions that are needed to produce the spike proteins. Vaccinated cells produce and display these spike proteins on their own surface.
The person’s immune system notices these foreign proteins and begins to create antibodies, which will protect the person if they are exposed to the real virus in the future.
One of the main features of the vaccine is that it does not need freezers for storage.
The Adenovirus virus vaccine is safe because the adenovirus cannot reproduce in human cells or cause disease, while the SARS-CoV-2 peak protein cannot cause covid-19 without the rest of the coronavirus.
This kind of empty strategy is not new. Johnson & Johnson used a similar method to produce the Ebola vaccine.
In fact, the vaccine developed by the University of Oxford and the Astra-Zeneca laboratory uses an adenovirus viral vector.
2. Is it effective?
The FDA analysis found that the vaccine Johnson & Johnson has an efficacy of 72% in the prevention of infection in all variants of Covid-19 and 86% efficacy in the prevention of severe cases of disease.
Although a vaccinated person can become infected, the data suggest that the vaccine reduces the risk that you will need hospitalization or that the disease will kill you.
A similar analysis was performed in South Africa, where a more contagious variant is dominant and obtained similar results.
The researchers noted that the Johnson & Johnson vaccine was slightly more effective in preventing disease there – 64% – but still 82% effective in preventing serious diseases.
Clinical trials were performed taking into account variants of the virus that occurred, for example, in South Africa.
The FDA also reported that this vaccine protects against other variants, such as those known in the United Kingdom and Brazil.
3. How it differs from other vaccines
The main difference is that Johnson & Johnson is a viral adenovirus vector vaccine, while Moderna and Pfizer are mRNA.
MRNA or messenger RNA vaccines use the genetic instructions of the coronavirus to tell the cells of vaccinated people to produce the top proteins, rather than using another virus as a vector.
And there are other differences, from a practical point of view.
so much Modern vaccines, such as Pfizer, are based on two doses, separated by a few weeks. Johnson & Johnson’s requires only one.
This is essential when there are not enough consumables.
In addition, the Johnson & Johnson vaccine does not require freezers for storage, unlike mRNA which requires a complex cold chain to be safely distributed.
Johnson & Johnson’s can be stored for three months in a regular refrigerator, making it easy to use and distribute.
In terms of their effectiveness, it is difficult to compare Moderna, Pfizer and vaccines Johnson & Johnson due to the difference in the design of clinical trials.
While Moderna and Pfizer have confirmed 95% efficacy in preventing the disease, clinical trials were conducted around mid-2020, before new variants of the virus appeared and became widely circulated.
Moderna and Pfizer vaccines may not be as effective against new variants, while Johnson & Johnson clinical trials have been conducted more recently and have considered efficacy against these new variants.
The Johnson & Johnson vaccine helps the vaccination effort around the world.
4. Is it recommended to choose one vaccine over the others?
Although the overall effectiveness of Moderna and Pfizer vaccines is higher than that of Johnson & Johnson, it is not recommended to wait until the desired vaccine is available.
In part, because this probably won’t happen for long, given the supply and demand issues.
The Johnson & Johnson vaccine is almost as good as mRNA-based vaccines for preventing severe cases, and that really matters.
Johnson & Johnson and other vector viral vaccines, such as Astra-Zeneca, are particularly important for the global vaccination effort.
From a public health perspective, it’s important to have more COVID-19 vaccines, so Johnson & Johnson’s is very welcome as part of that pandemic arsenal.
The Johnson & Johnson vaccine is expected to reach the countries most in need during the pandemic.
And it does not require a freezer, which makes transport and storage much easier.
It is a single injection vaccine that facilitates logistics compared to the organization that has to administer two doses per person.
In an attempt to vaccinate as many people as possible as soon as possible to limit the development of new variants of the coronavirus, Johnson & Johnson expects to deliver nearly four million doses to the United States as soon as the FDA eliminates it. use.
Having a third vaccine authorized in the US is a big step towards meeting the demand for vaccination and reducing the pandemic.
Maureen Ferran is a professor of biology at the Rochester Institute of Technology.
You can read this note originally published in English at Conversation.
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