Maureen Ferran, Rochester Institute of Technology
The U.S. Food and Drug Administration has approved the use of the Johnson & Johnson coronavirus vaccine in adults. Maureen Ferran, a virologist at Rochester Institute of Technology, explains how this third approved vaccine works and examines the differences between it and the moderna and Pfizer-BioNTech vaccines already in use.
1. How does the Johnson & Johnson vaccine work?
The Johnson & Johnson vaccine is a so-called viral vector vaccine.
To make this vaccine, the Johnson & Johnson team took a harmless adenovirus – the viral vector – and replaced a small portion of its genetic instructions with coronavirus genes for the SARS-CoV-2 spike protein.
After this modified adenovirus is injected into a person’s arm, it enters the person’s cells. The cells then read the genetic instructions necessary to make the spike protein, and the vaccinated cells make the spike protein and display it on their own surface. The person’s immune system then notices these foreign proteins and makes antibodies against them that protect the person in the event that they are ever exposed to SARS-CoV-2 in the future.
The adenovirus vector vaccine is safe because the adenovirus cannot replicate or cause disease in human cells, and the SARS-CoV-2 spike protein cannot cause COVID-19 without the rest of the coronavirus.
This approach is not new. Johnson & Johnson used a similar method to make their Ebola vaccine, and the AstraZeneca-Oxford COVID-19 vaccine is also an adenovirus vector viral vaccine.
2. How effective is it?
Analysis by the FDA found that Johnson & Johnson’s COVID-19 vaccine was 72% effective in preventing all COVID-19 and 86% effective in preventing severe cases of the disease in the United States. While there is still a chance that a vaccinated person could get sick, this suggests that they will have to go to hospital or die of COVID-19 much less often.
A similar experiment in South Africa, where a new, more contagious variant dominates, produced similar results. The researchers found that the Johnson & Johnson vaccine was slightly less effective at preventing all diseases – 64% overall – but still 82% at preventing major diseases. The FDA report also shows that the vaccine also protects against other variants from the UK and Brazil.
3. How is it different from other vaccines?
The most fundamental difference is that the Johnson & Johnson vaccine is an adenovirus vector vaccine while the Moderna and Pfizer vaccines are both mRNA vaccines. Messenger RNA vaccines use genetic instructions from the coronavirus to tell a person’s cells to make the spike protein, but these don’t use any virus other than a vector. There are also many practical differences.
Both mRNA-based vaccines require two shots. The Johnson & Johnson vaccine only requires a single dose. This is important when vaccines are scarce.
The Johnson & Johnson vaccine can also be stored at much warmer temperatures than the mRNA vaccines. The mRNA vaccines must be shipped and stored at sub-zero or freezing temperatures and require an intricate cold chain to safely distribute them. The Johnson & Johnson vaccine can be stored in a regular refrigerator for at least three months, which makes it much easier to use and distribute.
In terms of effectiveness, it is difficult to directly compare the Johnson & Johnson vaccine with the mRNA vaccines because clinical trials differ. While Moderna and Pfizer vaccines are about 95% effective in preventing COVID-19 disease, the studies were conducted in the summer and fall of 2020 before newer, more contagious variants became widely available. Moderna and Pfizer vaccines may not be as effective against the new variants, and Johnson & Johnson studies have recently been conducted taking into account the effectiveness of the vaccine against these new variants.
4. Should I choose one vaccine over another?
While the overall effectiveness of Moderna and Pfizer vaccines is higher than that of Johnson & Johnson’s vaccine, don’t wait to have your vaccine choice – which is probably still a long way off anyway. The Johnson & Johnson vaccine is almost as good as the mRNA-based vaccines at preventing serious diseases, and that’s what really matters.
The Johnson & Johnson vaccine and other viral vector vaccines such as AstraZeneca’s are particularly important to the global vaccination effort. From a public health perspective, having multiple COVID-19 vaccines is important, and the Johnson & Johnson vaccine is a very welcome addition to the vaccine arsenal. No freezer is required, which makes shipping and storage a lot easier. It is a one-shot vaccine that makes the logistics much easier compared to organizing two doses per person.
As many people as possible need to be vaccinated as soon as possible to limit the development of new coronavirus variants. Johnson & Johnson is expected to ship nearly four million doses once the FDA grants approval for the emergency. A third approved vaccine in the US will be a huge step towards meeting vaccination needs and stopping this pandemic.
Maureen Ferran, Associate Professor of Biology, Rochester Institute of Technology
This article is republished by The Conversation under a Creative Commons license. Read the original article.