The U.S. Food and Drug Administration has authorized the use of the Johnson & Johnson coronavirus vaccine in adults. Maureen Ferran, a virologist at the Rochester Institute of Technology, explains how this third authorized vaccine works and explores the differences between it and the Moderna and Pfizer–BioNTech vaccines that are already in use. Source: The Conversation 28 Feb 2021
1. How does the Johnson & Johnson vaccine work?
The Johnson & Johnson vaccine is what’s called a viral vector vaccine.
To create this vaccine, the Johnson & Johnson team took a harmless adenovirus – the viral vector – and replaced a small piece of its genetic instructions with coronavirus genes for the SARS-CoV-2 spike protein.
After this modified adenovirus is injected into someone’s arm, it enters the person’s cells. The cells then read the genetic instructions needed to make the spike protein and the vaccinated cells make and present the spike protein on their own surface. The person’s immune system then notices these foreign proteins and makes antibodies against them that will protect the person if they are ever exposed to SARS-CoV-2 in the future.
Our mission is to share knowledge and inform decisions.
The adenovirus vector vaccine is safe because the adenovirus can’t replicate in human cells or cause disease, and the SARS-CoV-2 spike protein can’t cause COVID–19 without the rest of the coronavirus.
2. How effective is it?
The FDA’s analysis found that, in the U.S., the Johnson & Johnson COVID-19 vaccine was 72% effective at preventing all COVID-19 and 86% effective at preventing severe cases of the disease. While there is still a chance a vaccinated person could get sick, this suggests they would be much less likely to need hospitalization or to die from COVID-19.
A similar trial in South Africa, where a new, more contagious variant is dominant, produced similar results. Researchers found the Johnson & Johnson vaccine to be slightly less effective at preventing all illness there – 64% overall – but was still 82% effective at preventing severe disease. The FDA report also indicates that the vaccine protects against other variants from Britain and Brazil too.
3. How is it different from other vaccines?
The most basic 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 another virus as a vector. There are many practical differences, too.
Both of the mRNA-based vaccines require two shots. The Johnson & Johnson vaccine requires only a single dose. This is key when vaccines are in short supply.
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 below–freezing or subzero temperatures and require a complicated cold chain to safely distribute them. The Johnson & Johnson vaccine can be stored for at least three months in a regular refrigerator, making it much easier to use and distribute.
As for efficacy, it is difficult to directly compare the Johnson & Johnson vaccine with the mRNA vaccines due to differences in how the clinical trials were designed. While the Moderna and Pfizer vaccines are reported to be approximately 95% effective at preventing illness from COVID–19, the trials were done over the summer and fall of 2020, before newer more contagious variants were circulating widely. The Moderna and Pfizer vaccines might not be as effective against the new variants, and Johnson & Johnson trials were done more recently and take into account the vaccine’s efficacy against these new variants.
4. Should I choose one vaccine over another?
Although the overall efficacy of the Moderna and Pfizer vaccines is higher than the Johnson & Johnson vaccine, you should not wait until you have your choice of vaccine – which is likely a long way off anyway. The Johnson & Johnson vaccine is nearly as good as the mRNA-based vaccines at preventing serious disease, and that’s what really matters.
The Johnson & Johnson vaccine and other viral-vector vaccines like the one from AstraZeneca are particularly important for the global vaccination effort. From a public health perspective, it’s important to have multiple COVID-19 vaccines, and the Johnson & Johnson vaccine is a very welcome addition to the vaccine arsenal. It doesn’t require a freezer, making it much easier to ship and store. It’s a one-shot vaccine, making logistics much easier compared with organizing two doses per person.
As many people as possible need to be vaccinated as quickly as possible to limit the development of new coronavirus variants. Johnson & Johnson is expected to ship out nearly four million doses as soon as the FDA grants emergency use authorization. Having a third authorized vaccine in the U.S. will be a big step towards meeting vaccination demand and stopping this pandemic.
Because it requires just one dose and has manageable temperature storage requirements, Johnson & Johnson’s vaccine is providing a much-needed boost to the U.S. immunization effort. The president confirmed that Johnson & Johnson will work with one of its competitors, pharmaceutical giant Merck, in a “historic partnership” to increase production of its vaccine, The Washington Post reported. President Biden also confirmed that he will use the Defense Production Act to speed the production of necessary equipment, machinery, and supplies.
Here’s everything you need to know about Johnson & Johnson’s vaccine—including how it works, its efficacy, and its side effects—plus how it compares to the other vaccines available in the U.S. so far.
How effective is the Johnson & Johnson COVID-19 vaccine?
The FDA’s approval is based on data from Johnson & Johnson’s global phase 3 clinical trial, which enrolled 43,783 people who were randomly given either a placebo or the Johnson & Johnson COVID-19 vaccine. The FDA’s analysis, which used data from 39,321 participants, found the Johnson & Johnson vaccine is about 66% effective at preventing moderate-to-severe COVID-19 at least 28 days after vaccination. When looking at data in the U.S. specifically, that number increases to about 74%.
What’s more, the vaccine is about 77% effective at preventing severe or critical forms of COVID-19 at least 14 days after vaccination, and 85% effective 28 days after vaccination—meaning its strength only builds with time. Again, its efficacy excels where it matters most: The company’s phase 3 trial reported no COVID-19-related deaths and no COVID-19 cases requiring medical intervention after 28 days in vaccinated participants.
The vaccine’s efficacy against moderate-to-severe COVID-19 did drop in South Africa—64% effective after 28 days—which is likely due to the highly infectious variant (B.1.351) dominating the region, says Richard Watkins, M.D., an infectious disease physician and professor of internal medicine at the Northeast Ohio Medical University. Related Stories How Does the AstraZeneca Vaccine Compare? Will the COVID-19 Vaccine Need a Booster Dose?
Although Pfizer-BioNTech and Moderna both offer COVID-19 vaccines with 95% efficacy, all of the available vaccines offer strong, worthwhile protection, as all of them have been shown to protect against severe illness and death, the two worst outcomes, says Dr. Watkins. He says it is worth noting that “the flu vaccine is usually up to 60% effective,” and that annual shot plays an integral role in decreasing flu-related hospitalizations and deaths every year.