The Belgian pharmaceutical company Janssen, part of the U.S. multinational Johnson & Johnson, has developed a viral vector vaccine. This method uses a vector, i.e. a different virus from SARS-CoV-2, to enter a cell and infect it. In this way, it uses the cellular machinery to produce the spike protein, present in this coronavirus, to generate antibodies.

Like most pharmaceutical groups, Janssen announced the start of its clinical trials in March 2020 and announced the results on 29 January 2021. About 43,783 volunteers from eight countries on three different continents took part in phase III clinical trials.

The main attraction of Janssen’s vaccine is that it is the first vaccine designed to be administered in a single dose, achieving 85% efficacy, according to early clinical trials. 

More than 30 countries have authorised its use, including members of the European Union, which will start receiving the first doses in the second half of April, the company said. The WHO has also endorsed this vaccine.

Like most vaccines, the most common reactions are headache, fatigue, pain at the injection site, fever, nausea and chills, among others. Rare side effects (one in 100 people) include shivering, excessive sweating, sneezing, sore throat, back pain and joint pain, among others. Hives and allergic reaction in the skin and subcutaneous tissue are listed as rare side effects, although according to data available at the end of March, it is not yet known whether this vaccine can cause a severe allergic reaction.

Janssen’s vaccine can be stored for up to two years at -20ºC and holds a maximum of three months between 2ºC and 8ºC.

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