What to Know About the Johnson & Johnson COVID-19 Vaccine

March 30, 2021

This article was medically reviewed by Dr. Ronald Nahass.

Since December 2020, the U.S. has been depending on two vaccines – the Moderna and Pfizer vaccines— to fight COVID-19. However, on February 27th, 2021, the U.S. Food and Drug Administration (FDA) assigned an emergency use authorization for the Johnson & Johnson vaccine, giving the U.S. a third alternative to help end the coronavirus pandemic.

In a statement from the FDA, Acting FDA commissioner Janet Woodcock, M.D., had this to say about the vaccine: “The authorization of [the Johnson & Johnson] vaccine expands the availability of vaccines, the best medical prevention method for COVID-19, to help us in the fight against this pandemic, which has claimed over half a million lives in the United States. The FDA, through our open and transparent scientific review process, has now authorized three COVID-19 vaccines with the urgency called for during this pandemic, using the agency’s rigorous standards for safety, effectiveness, and manufacturing quality needed to support emergency use authorization.”

The emergency approval of a third vaccine is a huge development in the fight against COVID-19, and in this blog, the infectious disease experts at ID Care will answer some of the most important questions about the Johnson & Johnson vaccine—from how it works to why it may be the answer to combatting emerging COVID-19 variants.

How Does the Johnson & Johnson Coronavirus Vaccine Work?

The first two vaccines approved by the FDA—the Moderna and Pfizer vaccines—require two shots, administered several weeks apart. The first dose provides partial immunity, while the second dose acts as a booster to ensure full protection from the virus that causes COVID-19.

The Johnson & Johnson immunization is a one-shot vaccine, which means the recipient is provided with full protection after only one dose. This is crucial as the vaccine rollout continues. A one-shot appointment is far less complicated than having to schedule a second immunization. Further simplifying the roll out process, the Johnson & Johnson vaccine—unlike the Moderna and Pfizer vaccines – does not require extreme cold to remain effective. In fact it can be stored for months at a standard refrigerator temperature. The vaccine is estimated to remain stable for two years at -4°F (-20°C), and a maximum of three months at routine refrigeration at temperatures of 36-46°F (2 to 8°C).

What is the Difference Between mRNA Vaccines and the Johnson & Johnson Vaccine?

The Pfizer and Moderna vaccines are made using messenger RNA (mRNA), a technology that delivers a bit of genetic code to cells in order to make the spike protein on the SARS-CoV-2 virus. The proteins made with the mRNA instructions activate the immune system, teaching it to see the spike protein as foreign and develop antibodies and other immunity weapons with which to fight it.

The Johnson & Johnson vaccine is an adenovirus vector vaccine, which uses a cold virus (vector) to deliver a gene that carries the blueprint for the spiky protein found on the surface of the coronavirus. The virus enters cells, which then follow the genetic instructions to construct a replica of the coronavirus spike. The immune system then uses these replicas to respond to the virus.

So, Does it Matter Which One a Person Gets?

At this point, it doesn’t matter which vaccine someone gets as all three vaccines have been clinically proven to prevent severe disease and hospitalization. So, anyone who is eligible to receive a vaccine should feel comfortable receiving the Moderna, Pfizer, or Johnson & Johnson immunization.

Keep in mind, a comparison on effectiveness isn’t exactly black and white as the trials for all three vaccines were done at different times during the pandemic, across different countries, using varying sets of people. However, additional studies are underway in the U.S. to gather more information on the effectiveness of all three COVID-19 vaccines in the real world over time.

How Effective was the Johnson & Johnson COVID-19 Vaccine in Clinical Trials?

All three available vaccines were observed to be extremely effective in trials. However, in the case of the Johnson & Johnson vaccine, U.S. trials concluded it was 100% effective in preventing hospitalization and death, 85% effective at protecting against severe cases of illness, and 72% effective at preventing infection overall.

With all three vaccines, immunity builds over a few weeks after immunization. Data from Johnson & Johnson shows that most vaccinated trial participants had a robust immune response 15 days after getting the shot, with significant protection reached by day 29. What’s more, the Johnson & Johnson vaccine’s effectiveness against severe disease has been found to increase over time to more than 90% within a month and a half after vaccination.

How Safe is the Johnson & Johnson COVID-19 Vaccine?

The Johnson & Johnson vaccine has been shown to have mostly mild side effects typically associated with vaccinations. The FDA will continue to monitor the safety of the Johnson and Johnson vaccine as it’s rolled out across the U.S., it has been shown to be very safe.

Side effects that have been reported with the Johnson & Johnson vaccine include pain, redness, and swelling near the injection site. Other general side effects include headache, feeling tired, muscle aches, nausea, and fever. It’s important to remember that while the Johnson & Johnson vaccine has been approved for emergency use, it is still being studied, and serious and unexpected effects may occur. However, the same could be said for the Moderna and Pfizer vaccines.

How Effective is the Johnson and Johnson Vaccine Against COVID-19 Variants?

According to analysis posted by the FDA, the Johnson & Johnson vaccine performed well against the variants first detected in Brazil and South Africa, because it was tested in both countries at a time when the variants were spreading there. This was not the case for the Moderna and Pfizer vaccine, so head-to-head comparison is difficult.

During clinical trials, Johnson & Johnson was able to track efficacy against emerging SARS-CoV-2 variants from the United Kingdom (B.1.1.7), South Africa (B.1.351), and Brazil (P.1)—showing around 60% efficacy for any infection against all three strains. It is highly protective for serious or life-threatening infection, approaching 100%, against the variants. Ultimately, the data from Johnson & Johnson indicates a moderate to strong efficacy against the widely circulating strains of SARS-CoV-2, however, there is limited data when it comes to efficacy against the newly emerging California and New York variants.

Johnson & Johnson CEO Alex Gorsky said that the company is well-positioned to adapt the vaccine for variants, and is working on rapid development of vaccine modifications that will “help address some of these new and emerging variants.”

When Can You Get the Johnson and Johnson Vaccine in New Jersey?

On March 1st, 2021, Johnson & Johnson began shipping nearly 4 million doses of its newly authorized COVID-19 vaccine across the U.S. Due to its ability to travel well—and last longer and in warmer temperatures than the Moderna and Pfizer vaccines— New Jersey plans to distribute the Johnson & Johnson vaccine to underserved communities, including communities of color, and vulnerable populations like people experiencing homelessness, those living in senior housing, homebound seniors, low-income residents, and people with disabilities.

New Jersey has received about 75,000 doses and doesn’t expect another shipment for at least three weeks. The Johnson & Johnson vaccine will be distributed across the state in locations such as Acme, ShopRite, and Wegmans supermarket pharmacies, as well as independent pharmacies in the most vulnerable communities. Hospitals will also use the vaccine in emergency rooms, where vulnerable populations are known to traffic more often.

At this time, individuals cannot select which vaccine they receive—be it Johnson & Johnson, Moderna, or Pfizer. However, right now, it is far more important to get vaccinated than concern oneself over which immunization is better. Scientific data shows that all three vaccinations are highly effective in providing protection against getting infected and will most likely stop the spread of COVID-19. Most importantly, all three vaccines have been shown to keep individuals from developing severe illness that may result in hospitalization or death.


As we continue through the pandemic, the Johnson & Johnson vaccine has given us yet another weapon to use against the coronavirus. This opportunity should not be taken lightly, and it should not be squandered. In the coming months, even more vaccines will become available to the public, and as the largest independent infectious disease practice on the East Coast, and the second largest in the United States, ID Care urges everyone to get vaccinated as soon as the opportunity arises. And remember, if you have any questions regarding COVID-19 vaccines, please don’t hesitate to give us a call at 908-281-0610 to speak with an ID Care expert or visit idcare.com to learn more.

COVID-19, Infectious Disease Blog, Nahass, Ronald