Coronavirus: Passive vaccines could ‘borrow’ immunity to protect frontline health staff

Frontline health workers could be immunised against COVID-19 within weeks, using a technique developed a century ago.

The simple but small-scale form of passive immunisation for those most in need could begin in a matter of weeks. Picture: AFP

Frontline health workers could be immunised against COVID-19 within weeks, using a technique that saved the lives of countless children a century ago and won the first Nobel prize in medicine.

An effective vaccine takes at least 12 months to develop, but “passive” immunisation that “borrows” the antibodies of recovered patients could give hospital staff stopgap protection, safeguarding their health, morale and expertise for future pandemics.

“Those people need to have something more than masks, gloves and a face shield,” says ­virologist Damian Purcell of the Melbourne medical research centre the Peter Doherty Institute for Infection and Immunity.

“Passive immunisation could prevent them acquiring infection if it works in the correct way.”

New York lost its first two ­nurses to COVID-19 by March 31. China’s virus whistleblower Li Wenliang, an ophthalmologist, was an early victim. In Italy, the death toll among physicians has passed 60. And Britain’s first doctor (Adil El Tayar, 63, a transplant specialist) died on March 25. ­Almost 14 per cent of Spain’s corona­virus cases are medical staff.

Doctors in several countries are alerting authorities to the value of passive immunisation, and Sydney surgeon John Stephen, who has an interest in immunotherapy, has urged government to get moving on public awareness and logistics.

“Scott Morrison was talking about those developing the vaccine as heroes, but the short-term heroes are going to be the people who donate the antibodies,” Dr Stephen said. “Ninety-nine per cent would be tickled pink to give their blood and save a life.

The Weekend Australian sought comment from the federal health department.

The simple but small-scale form of passive immunisation for those most in need could begin in weeks — the blood of recovered patients in Australia is already being collected and purified to remove anything infectious — while a modern, more potent form might be able to be ready for mass production in two to three months.

Either way, recipients get the passive benefit of others’ antibodies, whereas people actively produce their own antibodies after infection or an injected vaccine.

Both forms of passive immunisation are given by intravenous infusion. A vaccine can give lasting immunity but may take weeks to build up full protection. By contrast, its stopgap passive counterpart goes to work rapidly.

“As soon as the infusion is finished, it achieves its maximum dose, and there are ways of engineering these antibodies so that they remain protective in your circulation for up to six months,” Professor Purcell said.

With $3.2m from the Jack Ma Foundation, the Doherty Institute has begun research with the University of Melbourne and Royal Melbourne Hospital on passive immunisation against the SARS-CoV-2 virus that causes the illness COVID-19, as well as two possible active vaccines.

In a world-first, the institute has shown that vital antibodies are likely to appear in the blood six to eight days after a positive test for the virus, helping to guide the search for the most ­effective and safe antibodies so pharmaceutical companies can manufacture passive vaccines.

“It’s like finding a needle in a haystack. You need to have a very rigorous selection procedure to ­select the highest-quality antibody binding cells, then through genetic-engineering technology we can produce those antibodies in purity at extremely high levels,” Professor Purcell said.

Antibody test wanted

There is no test yet to screen in the community for people with antibodies to the virus, but work is under way.

Professor Purcell said some antibodies had to be avoided, and it was possible these “non-neutralising” antibodies were responsible for carrying the virus into the lungs, bringing on life-threatening pneumonia.

Unlike the more scattergun ­approach of 19th-century passive immunisation, the institute hopes to single out “monoclonal antibodies” that precisely target and neutralise the virus, drawing on promising work with HIV and some cancers.

“The fortunate thing is that we have some extremely experienced biopharmaceutical companies (such as CSL Ltd) that have large-scale production of these monoclonal antibodies as their business,” Professor Purcell said.

It’s understood the cost of this temporary protection could be something in the order of $30 million for 20 million doses, similar to the cost of an active vaccine, and in any case pursuit of the best neutralising antibodies is necessary for both passive and active immunisation efforts.

Professor Purcell hoped the institute’s candidate vaccine using monoclonal antibodies might be available in 2-3 months. “A lot could go wrong, we’re being optimistic here,” he said.

Assuming success with the research, the next steps would be fast-as-possible factory production and regulatory approval.

“Convalescent serum” was first used in the 1890s against diphtheria — which once cut short many childhoods — and led to the first Nobel prize in medicine for the German pioneer of immunology Emile von Behring in 1901. The technique is credited with halving fatality rates during the 1918-19 Spanish flu.

Convalescent serum has also been used to treat patients who are already sick. The ideal time to do this with COVID-19 is before patients who are especially vulnerable succumb to pneumonia, doctors believe.

Passive immunisation as a weapon against infectious diseases became overshadowed by antibiotics and modern vaccines but has been revived on a modest scale to contend with recent outbreaks of SARS1, MERS and Ebola, and updated with genetic technology and sophisticated processing for better targeting, effectiveness, safety and sheer volume.

Passive immunisation may serve as an emergency defence in biological warfare.

On March 23, New York governor Andrew Cuomo announced an emergency trial of convalescent plasma treatment for those critically ill with COVID-19. Mount Sinai Hospital physician Barron Lerner, who has just recovered from the disease, is one of thousands of people in the city to sign up as blood donors.

In Shenzen, China, five Chinese patients aged 36-65 were given convalescent plasma while on respirators with severe pneumonia and all showed improvement without apparent side-effects, according to an early research report on March 27. So far, there have been no randomised control trials to give strong evidence that passive immunisation will help fight COVID-19.