Leiden-based pharmaceutical company Janssen Vaccines has started testing a potential vaccine against the coronavirus in humans.

Earlier, the company thought it would be possible to start the so-called clinical test phase in September. However, the development of the vaccine has accelerated through a successful preclinical phase. The Dutch virologist Hanneke Schuitemaker (head of viral vaccines at Janssen) is leading this development.

Janssen & Johnson’s parent company, Johnson & Johnson, said last month that clinical trials would begin earlier “based on encouraging preclinical data and collaboration with authorities.”

The vaccine is initially being tested on 1045 healthy adults in the US and Belgium, ages 18 to 65.

‘Next phase in September’

The clinical phase mainly tests whether the vaccine is safe and what the possible side effects are. The actual effect of the vaccine will only be tested at a later stage, says Johan Van Hoof, head of Janssen’s vaccine program, to the Flemish broadcaster VRT.

“We hope to start that phase in September,” he says. “Then a lot more people will be recruited and then we’ll really see if the vaccine really protects against the virus, or if a serious illness caused by the virus occurs.”

If those results are encouraging, the vaccine could be available in the first half of 2021.


At least 163 potential corona vaccines are currently in development worldwide. At least 23 of these are currently being tested in humans, the rest are still in the phase of laboratory tests and animal experiments.

The vaccines from the Jenner Institute in Oxford and a Chinese vaccine are the most advanced in development. The first test results of those candidate vaccines on humans were promising.