Updated Information: Safety and Effectiveness of the Johnson & Johnson/Janssen COVID-19 Vaccine

Healthcare worker prepares a vaccine

Just like the Pfizer-BioNTech and Moderna vaccines, the Johnson & Johnson vaccine is given as a shot in the upper arm.

The FDA and the CDC said they have confidence that the Johnson & Johnson/Janssen vaccine is safe and effective in preventing COVID-19 for the vast majority of the US population and will save lives.

Mini Kamboj

Mini Kamboj

Memorial Sloan Kettering Chief Medical Epidemiologist Mini Kamboj explains why the J & J vaccine is effective and what authorities have learned about troubling but rare side effects.

Why should people have confidence that the J & J vaccine is safe and effective?

Health officials stress the risk of complications from COVID-19 itself is much higher than the risk of rare side effects from the vaccine.

In clinical trials involving more than 44,000 people, the J & J vaccine was 85% effective in preventing severe COVID-19.

While it’s unsettling to read about possible serious side effects from a vaccine, the investigations into the rare side effects linked to the J & J vaccine demonstrate how carefully any potential safety problems with vaccines are being evaluated by public health authorities.

CDC Director Dr. Rochelle Walensky said, “As we always do, we will continue to watch all signals closely as more Americans are vaccinated. I continue to be encouraged by the growing body of real-world evidence that the authorized COVID-19 vaccines are safe and effective, and they protect people from disease, hospitalization, and death.”

Back to top

What do I need to know about the FDA warning about the rare risk of Guillain–Barré syndrome after getting the J & J vaccine?

As of July 12, 2021, the CDC said that about 100 out of 13 million Americans who received the J & J vaccination developed Guillain-Barré syndrome.

Guillain-Barré syndrome is a serious condition in which the immune system attacks the nerves, but the data suggests the risk of developing this syndrome is very low. Of the few people who did, most were men over age 50 and experienced symptoms within six weeks of getting the shot.

Back to top

What are the symptoms of Guillain–Barré syndrome?

According to the J & J vaccine fact sheet, people should seek immediate medical attention if they experience any of the following symptoms:

  • weakness or tingling sensations, especially in the legs or arms, that worsen and spread to other parts of the body
  • difficulty walking; difficulty with facial movements, including speaking, chewing, or swallowing
  • double vision or an inability to move the eyes
  • difficulty with bladder control or bowel function
Back to top

Can Guillain-Barré syndrome be treated?

Guillain-Barré syndrome cannot be cured, but many symptoms of the disorder can be alleviated. Treatments can include a blood transfusion, pain medication, and physical therapy. The most severe effects of Guillain-Barré syndrome — loss of motor function and inability to walk — typically dissipate within a year of diagnosis.

Back to top

What do I need to know about blood clotting (cerebral vein sinus thrombosis with thrombocytopenia) after getting the J & J vaccine?

There have been a few cases in people who received the J & J vaccine of a highly unusual but severe disorder called cerebral vein sinus thrombosis with thrombocytopenia. The disorder is characterized by blood clots in the brain and other organs and low platelet counts.

An investigation by an advisory panel to the CDC found, as of April 21, 2021, a total of 15 cases of this disorder, including three deaths, out of approximately 8 million doses given. All cases were in women, and all but two cases occurred in women between 18 and 48 years old. Some of the patients had preexisting risk factors for blood clots; none were known to have cancer.

The CDC’s investigation determined the overall risk of developing the rare blood clotting disorder after receiving the J & J vaccine is extremely low.

Back to top

What are the symptoms of this blood clotting syndrome?

The initial symptoms include headache, fever, chills, shortness of breath, chest pain, nausea, vomiting, and persistent abdominal pain. In the few cases reported, these symptoms developed one to two weeks after receiving the J & J vaccine.

It’s important to note that the signs of this blood clotting disorder are different than the more common side effects that may be seen within the first few days after the vaccine, such as a mild headaches or flu-like symptoms. You can learn more about typical symptoms here.

Back to top

Can this blood clotting disorder be treated?

Yes. However, this syndrome occurring after vaccination is not treated like a typical blood clot, so it is important if you develop symptoms to let your healthcare provider know whether or not you received the J & J vaccine.

July 14, 2021

Additional Resources

Back to top