Skip navigation

COVID-19 Vaccine Janssen

COVID-19 Vaccine Janssen is developed by Janssen-Cilag International N.V. The European Comission gave the contitional marketing authorisation on the 11th of March 2021. COVID-19 Vaccine Janssen is a vaccine for preventing coronavirus disease 2019 (COVID-19) in people aged 18 years and older.

COVID-19 is caused by SARS-CoV-2 virus.

COVID-19 Vaccine Janssen is made up of another virus (of the adenovirus family) that has been modified to contain the gene for making a protein found on SARS-CoV-2.

COVID-19 Vaccine Janssen does not contain SARS-CoV-2 itself and cannot cause COVID-19.

As a precaution, after the vaccination, you should pay attention to your state of health to notice the possible symptoms of thrombosis or bleeding (read more about this from the leaflet of the vaccine). 

More details are available in the medication information that includes the leaflet inside the package. 

The maximum protection is achieved 14 days after the second dose. 

It’s recommended to use Janssen’s vaccine for people with mobility difficulties at their homes, or risk groups in the hospitals, or with other sound reasons for 1-dose vaccine. 

Additional information 

  • Janssen’s vaccine information on the website of the European Medical Agency is HERE
  • Questions and answers about Janssen vaccine (in Estonian) on the website of the Estonian Medical Agency are  HERE
  • The information about the Jannsen vaccine (SPC) (in Estonian) is available HERE.
How it works?

COVID-19 Vaccine Janssen works by preparing the body to defend itself against COVID-19. It is made up of another virus (an adenovirus) that has been modified to contain the gene for making the SARS-CoV-2 spike protein. This is a protein on the SARS-CoV-2 virus which it needs to enter the body’s cells.

The adenovirus passes the SARS-CoV-2 gene into the vaccinated person’s cells. The cells can then use the gene to produce the spike protein. The person’s immune system will recognise the spike protein as foreign and produce antibodies and activate T cells (white blood cells) to target it.

Later, if the person comes into contact with SARS-CoV-2 virus, the person’s immune system will recognise the spike protein on the virus and be ready to defend the body against it.

The adenovirus in the vaccine cannot reproduce and does not cause the disease.

Possible side effects

The most common side effects with COVID-19 Vaccine Janssen in the trials were usually mild or moderate and got better within 1 or 2 days after vaccination.

The most common side effects are pain at the injection site, headache, tiredness, muscle pain and nausea. They may affect more than 1 in 10 people.

Coughing, joint pain, fever, chills, as well as redness and swelling at the injection site may affect up to 1 in 10 people. Sneezing, tremor, dizziness, paraesthesia (unusual sensations like numbness, tingling, or pins and needles), throat pain, rash, sweating, diarrhoea, muscle weakness, pain in the arms and legs, backache, weakness, and feeling generally unwell may affect up to 1 in 100 people.

Allergic reactions, including anaphylaxis (severe allergic reaction), have occurred in people receiving the vaccine. As for all vaccines, COVID-19 Vaccine Janssen should be given under close supervision with appropriate medical treatment available.

What's the efficacy?

Results from a clinical trial involving people in the United States, South Africa and Latin American countries found that COVID-19 Vaccine Janssen was effective at preventing COVID-19 in people from 18 years of age. This study involved over 44,000 people. Half received a single dose of the vaccine and half were given placebo (a dummy injection). People did not know if they had been given COVID-19 Vaccine Janssen or placebo.

The trial found a 67% reduction in the number of symptomatic COVID-19 cases after 2 weeks in people who received COVID-19 Vaccine Janssen (116 cases out of 19,630 people) compared with people given placebo (348 of 19,691 people). This means that the vaccine had a 67% efficacy.

The ingredients of Janssen's vaccine

One dose (0.5 mL) contains:
Adenovirus type 26 encoding the SARS-CoV-2 spike glycoprotein* (Ad26.COV2-S), not less than
8.92 log10 infectious units (Inf.U).

  • Produced in the PER.C6 TetR Cell Line and by recombinant DNA technology.
    The product contains genetically modified organisms (GMOs).

Other ingredients:

2-hydroxypropyl-β-cyclodextrin (HBCD)
Citric acid monohydrate
Ethanol
Hydrochloric acid
Polysorbate-80
Sodium chloride
Sodium hydroxide
Trisodium citrate dihydrate
Water for injection

Everything you should know about the COVID-19 vaccination

Vaccination is free of charge for all people living in Estonia, even without the national health insurance.
  • Vaccination is voluntary.
  • Vaccination is open to all people who are at least 5 years old.
  • Compared to COVID-19 illness, vaccination is safe, and generally, the side effects pass quickly.
  • Booster doses are available only for adults, and the time for a booster jab is 2 months after finishing the vaccination course with the Janssen vaccine, and 3 months after finishing the vaccination course with AstraZeneca, Pfizer/BioNTech and Moderna vaccines.
Scroll to top