How long does it take to develop a vaccine?

Julie Steenhuysen -

Drugmakers are working as quickly as possible to develop a vaccine to combat the rapidly spreading coronavirus that has infected more than 100,000 people worldwide.

Behind the scenes, scientists and medical experts are concerned that rushing a vaccine could end up worsening the infection in some patients rather than preventing it.

Studies have suggested that coronavirus vaccines carry the risk of what is known as vaccine enhancement, where instead of protecting against infection, the vaccine can actually make the disease worse when a vaccinated person is infected with the virus. The mechanism that causes that risk is not fully understood and is one of the stumbling blocks that has prevented the successful development of a coronavirus vaccine.

Normally, researchers would take months to test for the possibility of vaccine enhancement in animals. Given the urgency to stem the spread of the new coronavirus, some drugmakers are moving straight into small-scale human tests, without waiting for the completion of such animal tests.

“I understand the importance of accelerating timelines for vaccines in general, but from everything I know, this is not the vaccine to be doing it with,” Dr Peter Hotez, dean of the National School of Tropical

Medicine at Baylor College of Medicine, said.

Hotez worked on development of a vaccine for SARS (Severe Acute Respiratory Syndrome), the coronavirus behind a major 2003 outbreak, and found that some vaccinated animals developed more severe disease compared with unvaccinated animals when they were exposed to the virus.

“There is a risk of immune enhancement,” said Hotez. “The way you reduce that risk is first you show it does not occur in laboratory animals.” Hotez testified last week before the US House Committee on Science, Space and Technology about the need for sustained funding for vaccine research. There remains no vaccine for any of the new coronaviruses that have caused outbreaks in the past 20 years.

At least for now, the world’s experts have concluded that accelerated testing is a risk worth taking.

At a specially convened World Health Organization (WHO) meeting in mid-February, designed to co-ordinate a global response to the new coronavirus, scientists representing government-funded research organisations and drugmakers around the world agreed that the threat was so great that vaccine developers should move quickly into human trials, before animal testing is completed.

“You want to have a vaccine as quickly as possible,” Dr Marie-Paule Kieny, former assistant director-general at the WHO, who co-chaired the meeting, said. “You have to balance this with the risk that you impose on a very small number of people, and do all you can do to mitigate this risk as much as possible.” The conclusion of that meeting, which was not open to media, has not been officially publicised by the WHO. It does not reflect any official position adopted by the WHO, a United Nations body whose job it is to help shape global health policy.

Regulatory oversight of drugmakers and medical research is in the hands of national regulators. The most powerful of those, the US Food and Drug Administration (FDA), has signalled that it is in agreement with the consensus and will not stand in the way of accelerated testing schedules.

“When responding to an urgent public health situation such as novel coronavirus, we intend to exercise regulatory flexibility and consider all data relevant to a certain vaccine platform,” FDA spokeswoman Stephanie Caccomo said in a statement. The agency had no comment specifically on animal testing for vaccine enhancement.

Coronavirus vaccine developers are still required to conduct routine animal testing to make sure the vaccine itself is not toxic and is likely to help the immune system respond to the virus.

Some 20 coronavirus vaccine candidates are being developed by research institutes and drugmakers including America’s Johnson & Johnson and France’s Sanofi SA. The US government has earmarked more than $3 billion for coronavirus treatments and vaccines.

— Reuters