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What to Know About the Johnson & Johnson COVID Vaccine

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Key Takeaways

  • After an earlier pause, the Johnson & Johnson (J&J) vaccine is recommended by the CDC and the FDA.
  • It's formulated differently than the Pfizer and Moderna vaccines, but effective against severe illness, hospitalization, and death related to COVID-19.
  • Women younger than 50 years old should be aware of the rare risk of blood clots with low platelets after vaccination.
  • A booster shot for the J&J vaccine shows promise in clinical trials and may soon become available.


In early 2021, corporate powerhouse Johnson & Johnson (J&J) introduced its own vaccine in the fight against COVID-19. Developed by the company’s pharmaceutical arm Janssen, the J&J vaccine has a different formulation than the Pfizer or Moderna vaccines and requires only a single dose to be effective.

After some early stops and starts, including a temporary pause in its availability as rare cases of blood clots were being investigated, the J&J vaccine is recommended by the Centers for Disease Control (CDC) and approved for emergency use authorization in people ages 18 and older by the Food and Drug Administration (FDA).

How Does the J&J Vaccine Differ From Pfizer and Moderna?

The J&J vaccine was designed to be slightly different from the vaccines made by Pfizer and Moderna. First, it's initially delivered in a single dose instead of a series of two shots.

Also, the J&J shot is an adenovirus-vectored vaccine rather than an mRNA vaccine. That’s science-speak for a vaccine that uses a common cold virus (commonly called an adenovirus) to hitchhike the coronavirus genes to produce those same viral proteins, explains Dr. Nitin Desai, MD, CEO, and chief medical officer of COVID PreCheck.

Partly because of this, the J&J vaccine has been shown to have a slightly lower rate of effectiveness than its counterparts. Both the Moderna and the Pfizer vaccine boast effectiveness rates in the mid-90% range, while global data suggests that J&J's vaccine is 85% effective at preventing severe or critical COVID symptoms.

It's worth noting, though, that early clinical trials showed that J&J's vaccine offered complete protection against hospitalization and death from COVID after 28 days. More recent research, of healthcare workers in South Africa, showed the J&J shot to be up to 96% effective against death from the Beta and Delta variants, specifically.

Pfizer's is still the only vaccine that has received a formal FDA stamp of approval, above and beyond an emergency-use authorization.

In late August 2021, J&J released data supporting the use of a booster shot for all people who received a single dose of its vaccine. In trials, people treated with a booster shot had antibodies nine times higher than those who received a single shot of the vaccine. The company says it's working with the FDA and CDC to gain clearance and formulate a plan to roll out booster doses soon.

Is the J&J Vaccine Safe? 

Yes. According to Desai, “The Johnson & Johnson vaccine has an acceptable safety profile and could be an alternative for some with a history of allergies to other vaccines or their ingredients.”

That’s great news for people who might be naturally wary of vaccines and thus struggling with the decision to get this important shot. “In clinical trials, there have been fewer severe side effects from the J&J vaccine, including reactions like anaphylaxis,” Desai says.

Blood Clot Risks

After reports of six people experiencing a rare and severe type of blood clot after receiving the J&J vaccine, the use of the vaccine was paused to conduct a thorough safety review. The FDA and CDC subsequently lifted the pause, deeming the vaccine safe and effective for use in the U.S.

To date, 44 individuals are known to have developed a blood clotting syndrome after the J&J vaccine. (For context, over 14 million doses have been administered so far.) The CDC states the benefits of the vaccine still outweigh its risks but counsels women under 50 to consider choosing the Pfizer or Moderna vaccine if they are concerned.

Should You Get the J&J Vaccine If You're Pregnant?

In studies conducted to date, there is no evidence that there is a detrimental effect of the COVID vaccine on pregnancy, says Dr. Barry Witt, a board-certified reproductive endocrinologist and medical director for WINFertility.

“One concern that has been raised is that the coronavirus’s spike protein shares small stretches of the same genetic code as placental protein, and that this could result in an immune reaction against the placenta,” Witt says. “However, these proteins are otherwise completely different in structure and the vaccine does not induce an immune reaction against the placental protein, so this should not be a concern.”

The American College of Obstetricians and Gynecologists (ACOG), the Society for Maternal-Fetal Medicine (SMFM), and the American Society for Reproductive Medicine (ASRM) all recommend COVID-19 vaccination for people who are pregnant or trying to conceive. ACOG notes that while it considers the J&J vaccine safe for pregnant people, those concerned about rare cases of blood clots can opt for the Pfizer or Moderna vaccines instead.

Studies show that COVID-19 puts a person at higher risk for severe complications during pregnancy. Additionally, research shows that COVID-19 vaccines actually seem to confer helpful COVID-fighting antibodies to your baby once they're born.

If you are pregnant and have questions about COVID-19 vaccination, the CDC recommends reaching out to MotherToBaby to discuss your concerns with experts trained by the non-profit Organization of Teratology Information Specialists (OTIS). You can call 1-866-626-6847 or start a live chat.

What About My Kids?

Currently, people have to be 18 years or older to get the J&J as well as the Moderna vaccines. Children ages 12 and up can receive the Pfizer vaccine.

Children were not a part of initial J&J clinical trials, and they will not be eligible to receive the vaccine until it is shown to be effective—and safe—for younger teens and kids. That makes it all the more important for adults to be vaccinated.

On April 2, Johnson & Johnson announced that it had begun testing its vaccine on adolescents between ages 12 and 17. It does plan to test the vaccine on infants, pregnant women, and people who are immunocompromised as well, but specifics have not yet been released.

Fortunately, evidence continues to show that kids are more likely to experience less severe COVID symptoms if they do become infected.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

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