The Johnson & Johnson vaccine only requires a single dose.
The U.S. Food and Drug Administration (FDA) this week authorized the use of the covid-19 vaccine in adults developed at Johnson & Johnson Laboratories.
The main feature of this vaccine is that, unlike others that are already in use, it works with a single dose.
Maureen Ferran, a virologist at the University of Rochester, explains how this vaccine works, the third authorized by the FDA, and its differences with those manufactured by Pfizer-BioNTech and Moderna.
1. How does the Johnson & Johnson vaccine work?
This 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 from the beak proteins (the outer parts of a virus that look like a crown). SARS-CoV-2, the virus that produces covid-19.
Then this adenovirus modified it is injected into the patient’s arm and enters their cells.
The cells then read the genetic instructions that are needed to produce the beak proteins. Vaccinated cells produce and display these beak 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 deep freezers to be stored.
The adenovirus viral vector vaccine is safe because the adenovirus cannot replicate in human cells or cause disease, while the SARS-CoV-2 peak protein cannot cause covid-19 without the rest of the coronavirus.
This type of vaccine strategy is not new. Johnson & Johnson used a similar method to produce the Ebola vaccine.
In fact, the vaccine developed by Oxford University and the Astra-Zeneca laboratory uses an adenovirus viral vector.
2. Is it effective?
FDA analysis found that the vaccine Johnson & Johnson shows 72% efficacy in preventing infection in all variants of covid-19 and 86% efficacy in preventing severe cases of the disease.
Although a vaccinated person can be vaccinated, the data suggest that the vaccine reduces the risks that hospitalization requires or that the disease causes his death.
A similar analysis was conducted in South Africa, where a much more contagious variant is the dominant one, and yielded similar results.
The researchers noted that the Johnson & Johnson vaccine was slightly less effective in preventing the disease – 64% – but still showed 82% effectiveness in preventing serious conditions.
Clinical trials were conducted taking into account virus variants that appeared, 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 an adenovirus viral vector vaccine, while Moderna and Pfizer are mRNA-type.
MRNA vaccines, or RNA messengers, use the genetic instructions of the coronavirus to tell the cells of vaccinated people to produce beak proteins, instead of 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 the administration of two doses, Separated for several weeks. Johnson & Johnson’s requires only one.
This is key when there are not enough supplies.
In addition, the Johnson & Johnson vaccine does not need deep-freezers for storage, unlike mRNAs that require a complex cold chain to be safely distributed.
Those from Johnson & Johnson can be stored for three months in a regular refrigerator, which facilitates their use and distribution.
Regarding its effectiveness, it becomes difficult to compare the vaccines of Moderna, Pfizer and Johnson & Johnson due to the difference in the design of the clinical trials.
While Moderna and Pfizer confirmed 95% efficacy in preventing the disease, clinical trials were conducted in mid-2020, before new virus variants appeared and had widespread circulation.
It is very possible that Moderna and Pfizer vaccines are not as effective against new variants, While Johnson & Johnson clinical trials were conducted more recently and took into account efficacy in the face of these new variants.
The Johnson & Johnson vaccine helps in 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 you have the vaccine you want available.
Partly because this probably won’t happen for long, given the demand and supply issues.
The Johnson & Johnson vaccine is almost as good as mRNA-based vaccines to prevent serious cases, and that’s what really matters.
Johnson & Johnson and other viral vector vaccines, such as Astra-Zeneca, are particularly important for the global vaccination effort..
From a public health perspective, it is important to have several covid-19 vaccines, so Johnson & Johnson’s is very welcome as part of this pandemic arsenal.
The Johnson & Johnson vaccine is expected to reach the most needy countries during the pandemic.
And it doesn’t require a freezer, so it’s much easier to ship and store.
It’s a single-shot vaccine, whatever facilitates logistics compared to the organization required to administer two doses per person.
In attempts to vaccinate as many people as possible as quickly as possible to limit the development of new variants of the coronavirus, Johnson & Johnson is expected to dispatch nearly four million doses soon in the U.S., as soon as the FDA authorizes its emergency use.
Having a third vaccine authorized in the US is a big step in meeting the demand for vaccination and curbing the pandemic.
Maureen Ferran is Professor of Biology at the Rochester Institute of Technology.
You can read this note originally published in English at The conversation.
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