The new Johnson & Johnson vaccine is being distributed in many states as a third option—following the Pfizer and Moderna vaccines—for becoming immunized against COVID-19. The J&J vaccine is slightly different in how it’s administered and how it affects the body, but like the other vaccines it prevents severe cases of COVID-19 that could lead to hospitalization or death.
Here is our guide to the biggest questions people have about the new vaccine, and what to expect if you get the new J&J vaccine for COVID-19.
Is the J&J Vaccine Safe and Effective?
The new J&J vaccine for COVID-19 is considered safe, since all studies of the vaccine found no allergic reactions or adverse effects. It can cause side effects that feel like getting sick—chills, fever, aches and pains, sore muscles, etc.—but it’s impossible to get COVID-19 from the vaccine. It has been authorized for use under emergency orders from the FDA, so all potential adverse effects have not been studied over the long-term. However, from all available evidence it seems to be a very safe vaccine.
The vaccine was found in existing studies to be 66% effective at preventing infection from COVID-19 and 85% effective at preventing moderate illness. This is less effective than Pfizer and Moderna vaccines, which are 95% effective at preventing infection after their two doses are complete.
However, all three vaccines are 100% effective at preventing hospitalization and/or death from COVID-19. For this reason, the FDA has authorized its use and begun distributing it.
What Are the Side Effects of the J&J Vaccine?
Like all the COVID-19 vaccines, the J&J vaccine does cause some symptoms in the days after receiving the shot. Soreness at the injection site, flu-like symptoms such as fever, chills, and aches are common. Being very tired is also a common effect, so getting the shot the day before a day you can take extra time to sleep can help.
While these flu-like symptoms are uncomfortable, they won’t last longer than a couple days and it’s impossible to actually get COVID-19 or any other illness from the vaccine. The flu-like symptoms are caused by your immune system reacting to the vaccine, so they are actually a sign that it’s working.
How Is It Different From Other COVID-19 Vaccines?
The J&J vaccine is built from an existing virus called an adenovirus that has some DNA taken from the virus that causes COVID-19. Adenovirus causes respiratory illness, but the part that can cause disease is removed from its DNA.
The weakened adenovirus DNA is then modified to produce proteins on its surface that look like the ones found on the surface of COVID-19, which allows your immune system to learn how to identify and destroy anything that carries these proteins.
The Pfizer and Moderna COVID-19 vaccines, on the other hand, both use a new type of mRNA technology. The mRNA is a small piece of genetic information that only codes for the proteins found on the surface of COVID-19.
The main difference between the vaccine for manufacturers and distributors is that the J&J vaccine is more stable because it uses DNA instead of mRNA, so it doesn’t require ultra-cold storage. This makes it easier to distribute to many people at once. From the perspective of a person receiving the COVID-19 vaccine, both types will have similar effects.
The other main difference is that the J&J vaccine has only one dose, while the other vaccines require two doses four weeks apart.
The Pfizer and Moderna vaccines are slightly more effective at preventing COVID-19—66% vs. 95%—but all are 100% effective at preventing hospitalization and death in existing studies. The official recommendation is to take any vaccine available to you in your area as soon as possible to stay safe.
Which Vaccine Should I Get?
Because the supply is so limited, the best answer for most people is to get whatever is available to you where you live first. The Pfizer and Moderna vaccines are slightly more effective, and the J&J vaccine is more convenient since it’s only one dose, but otherwise they are very similar from the perspective of the person receiving the vaccine. They all have a 100% success rate at preventing hospitalization and death from COVID-19.