The Janssen (Johnson & Johnson) COVID-19 Vaccine in Pregnancy

The information provided below is for readers based in the United States of America. Readers outside of the United States of America should seek the information from local sources.

Active ingredient

Recombinant DNA encoding the SARS-CoV-2 viral spike (S) protein

Delivery vehicle

Replication-incompetent recombinant adenovirus type 26 (Ad26)

Method of administration

Deltoid IM injection

Recommended schedule

Single injection (WHO, Janssen, as of Aug 24, 2021).

Dosage per shot

Adult: 0.5 mL


18 years and older (As of Aug 24, 2021)


Against ancestral strain of SARS-CoV2: 66.9 percent (95% CI; 59.0,73.4) against symptomatic SARS-CoV-2 infection. 76.7 percent (95% CI: 54.6, 89.1) against severe COVID-19 disease after 14 days, and 85.4% after 28 days. Vaccine efficacy against hospitalizations reported at 93.1 percent (95% CI: 72.7, 99.2) after 14 days and 100.0 percent (95% CI: 74.3, 100.0) after 28 days. Efficacy has been maintained against variants in Brazil and South Africa (gamma, beta). Efficacies are maintained across genders, ages, and ethnicities. As maintenance of efficacy over time against the Delta (B.1.172.2) variant, studies are ongoing as of late August 21. However, preprint data posted on medRxiv (awaiting peer review), suggest immunity (both humoral and cellular) is maintained very well against the Delta variant —slightly better than against some other variants— up to 239 days (8 months) from the initial dose.


As of late August 2021, a trial (HORIZON 1) is gearing up of the Janssen vaccine in healthy, pregnant volunteers. Meanwhile, the vaccine is recommended “if the benefit of vaccinating a pregnant woman outweighs the potential vaccine risks” (WHO). Currently, the benefits of COVID-19 vaccination, by any of the approved vaccines, far outweigh potential risks both in pregnancy and lactation. However, globally, there is an abundance of policies and philosophies surrounding to what degree potential vaccine recipients should be able to assess the risk vs benefits on their own. There is no plausible mechanism supporting notions that this vaccine, or any of the approved COVID-19 vaccines, might present a particular danger during pregnancy or lactation. Maternal vaccination against SARS-CoV2 may possibly protect newborns and nursing infants against endemic variants of SARS-CoV2, including the Delta variant, while pregnancy is a risk factor for the development of severe COVID-19 in unvaccinated women and for preterm birth. Pregnant women older than 35 years and those with a high body mass index

Relation to Pregnancy and Lactation

(BMI) are considered to have an elevated risk of developing symptomatic and severe COVID19. Vaccine efficacy is thought to be the same in lactating women as in non-lactating adults

Adverse effects

Injection site : pain, erythema, swelling at injection site

Systemic : fatigue, malaise, headache, myalgia, chills, fever, nausea, arthralgia, diarrhea

Similar to the other approved COVID19 viral vector vaccine, AZD1222 (Oxford- AstraZeneca), there have been a scattering of reported cases of thrombotic events in women who have received Ad26.COV2.S. Amounting to a very small number of cases, the reports include central venous thrombosis and cerebral venous sinus thrombosis with thrombosis with thrombocytopenia syndrome (TTS), which is a heparin-induced thrombocytopenia (HIT)-like syndrome. Rather than influencing a woman’s risk-benefit assessment of the Janssen vaccine, the main significance of such reports is for physicians and other health care professionals. Faced with a patient who has received Ad26.COV2.S whose presentation suggests possible TTS, the health care professional should avoid heparin and opt instead for one of the newer anticoagulants that acts through a different mechanism, such as argatroban, fondaparinux, or rivaroxaban, or administer intravenous immunoglobulin therapy (Lai et al. 2021).

Pregnancy and Lactation Positions by Country for the Johnson & Johnson Vaccine (Janssen)

FDA Fact Sheet for Recipients and Caregivers


Janssen. EMERGENCY USE AUTHORIZATION (EUA) OF THE JANSSEN COVID-19 VACCINE TO PREVENT CORONAVIRUS DISEASE 2019 (COVID-19). FACT SHEET FOR HEALTHCARE PROVIDERS ADMINISTERING VACCINE. https://www.janssenlabels.com/emergency-use-authorization/Janssen+COVID-19+Vaccine-HCP-fact-sheet.pdf. Updated July 8; Accessed August 24, 2021

Lai CC, Ko WC, Chen CJ, Chen PY, Huang YC, Lee PI, Hsueh PR. COVID-19 vaccines and thrombosis with thrombocytopenia syndrome. Expert Rev Vaccines. 2021 Jul 8:1-9. doi: 10.1080/14760584.2021.1949294. Epub ahead of print. PMID: 34176415.

Lopez Bernal J, Andrews N, Gower C, et al. Effectiveness of Covid-19 vaccines against the B.1.617.2 (delta) variant. N Engl J Med. DOI: 10.1056/NEJMoa2108891.

Smadja DM, Yue QY, Chocron R, Sanchez O, Lillo-Le Louet A. Vaccination against COVID-19: insight from arterial and venous thrombosis occurrence using data from VigiBase. Eur Respir J. 2021 Jul; 58(1): 2100956.

Sadoff J, Gray G, Vandebosch A et al. Safety and Efficacy of Single-Dose Ad26.COV2.S Vaccine against Covid-19. N Engl J Med 2021; 384:2187-2201 DOI: 10.1056/NEJMoa2101544

Society of Obstetricians and Gynaecologists of Canada. Statement on COVID-19 Vaccination in Pregnancy. https://sogc.org/en/content/featured-news/SOGC_Statement_on_COVID-19_Vaccination_in_Pregnancy.aspx Accessed August 24, 2021

World Health Organization. Interim recommendations for the use of the Janssen Ad26.COV2.S (COVID-19) vaccine. https://www.who.int/publications/i/item/WHO-2019-nCoV-vaccines-SAGE-recommendation-Ad26.COV2.S-2021.1 First issued 17 March 2021; Updated 15 June 2021. Accessed August 24, 2021

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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