Safe nCov coronavirus vaccine may take years

The claims of multiple vaccine developers that an nCov coronavirus vaccine may soon be in our hands are misleading and don’t tell the full story, says globally renowned vaccine expert Professor Nikolai Petrovsky of Flinders University in Adelaide.

The claims, which have dominated headlines for the past several weeks, suggest that we may be only a few months away from getting an nCov vaccine to curb the pandemic spread, which has already infected around 30,000 people, resulting in more than 800 reported deaths to date.

However, Petrovsky warns that these claims are giving us false hope, given the many challenges of vaccine development, the long duration needed for vaccine safety testing and the current lack of nCoV animal challenge models to test any new vaccines.

“On the one hand, there are a number of new and innovative methods of vaccine development — including those which involve the use of computer modelling and AI. These tools have the potential to drastically accelerate vaccine design, trimming years off the traditional process,” he told Hospital + Healthcare.

“But on the other hand, we know from our experience of developing a SARS coronavirus vaccine 17 years ago that coronavirus vaccines — particularly those using aluminium salts as adjuvants — can cause a problem known as vaccine-enhanced disease (a rare but serious immunity dysfunction).

“This can result in a worse, rather than better, clinical outcome when immunised subjects become exposed to the virus.

“Although we were able to develop a new and safe adjuvant for the SARS vaccine, we don’t yet know the likely behaviour of nCoV vaccines and whether these might cause vaccine-enhanced disease,” Petrovsky said.

“This will need to be tested using animal challenge models which currently do not exist. It is possible that humanised, ACE2 transgenic mice — as used for SARS vaccine testing — may be suitable, but confirming this will take time,” he added.

“Only when animal testing is complete will it be safe to undertake progressively larger clinical trials and establish whether an nCoV vaccine is effective and safe for humans — before, finally, making it publicly available to at-risk populations.”

The upshot of this, he argued, is that it is likely to take several years or more to develop a safe and effective nCov vaccine. In the meantime, fast diagnosis, quarantine and infection control measures such as regular handwashing and face masks are likely the best means of curbing nCoV spread.

But despite the delay, Petrovsky added that developing a vaccine may still be worthwhile. “It’s possible that the nCov virus might establish itself as a “perpetual human pathogen”, like influenza virus. In this case, an nCov vaccine could make a valuable contribution to future health care.”

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