EXPLAINER

Coronavirus: Why a vaccine mightn't be the magic bullet

A vaccine won't suddenly return us to what we once thought was normality. Picture: Picture: Sitthixay Ditthavong
A vaccine won't suddenly return us to what we once thought was normality. Picture: Picture: Sitthixay Ditthavong

There are 200 potential vaccines being worked on around the world with eleven of those projects in phase 3 trials on large numbers of people.

Experts are optimistic that one of those groups of researchers will produce a vaccine, perhaps by the end of the year.

But that doesn't mean that "normality" will return soon after. We may have assumed that it'll be like a flu jab - we get one every year and then go about our lives knowing we are unlikely to catch flu.

It may not be like that.

Why won't there be an on-off switch which clicks us back to normal life?

Firstly, let's state what must be said: it is not certain that an effective and safe vaccine will emerge - it's likely but not 100 per cent guaranteed.

But let's be optimistic and assume one does get produced.

The key thing is how effective it will be.

The common view among experts is that it would need to be at least 50 per cent effective. In other words, if 100 people are vaccinated, 50 will be protected from infection - but the other 50 won't be.

But even that would be "fantastic", according to epidemiologist Adrian Esterman, a professor at the University of South Australia.

He said the current flu vaccine was 40 to 60 per cent effective - but that is enough to cut the chances of catching flu dramatically because so many would be immune.

And a vaccine might prevent the most severe symptoms in those who did catch COVID-19. That, in itself, would relieve the burden on hospitals.

"That would be a game-changer. Our hospitals could handle it. Beds would be available," Professor Esterman told Australian Community Media.

He also thinks that a less effective vaccine would become a more effective vaccine as research revealed how it could be tweaked and improved.

Why doesn't a vaccine have to be 100 per cent effective?

The World Health Organisation gives a hypothetical example:

"In a high school of 1,000 students, none has ever had measles.

All but five of the students have had two doses of measles vaccine, and so are fully immunized. The entire student body is exposed to measles, and every susceptible student becomes infected.

The five unvaccinated students will be infected, of course. But of the 995 who have been vaccinated, we would expect several not to respond to the vaccine.

"In this class, seven students do not respond, and they, too, become infected. Therefore seven of 12, or about 58 per cent of the cases occur in students who have been fully vaccinated."

But that is still better - a lot better - than a mass of people being infected which is what would have happened without vaccination.

Some hurdles

Scientists don't know how long protection from one jab of a vaccine might last - will a booster be needed?

Immune systems weaken with age so it's not clear if a vaccine would work so well for older people. Perhaps a cocktail of vaccines might be needed, with different products better suited to different sorts of people.

There is already resistance to vaccines - "vaccine hesitancy". Would those who object to masks and lockdowns also refuse vaccination?

What about vaccine refusers?

The could be a real problem, according to Professor Esterman.

In the United States, some polls indicate that 60 per cent of the population are hesitant about vaccines. There is a swathe of people who mistrust government who, swayed by misinformation on the internet, might refuse.

Professor Esterman thinks the proportion of vaccine opponents is smaller in Australia - but it might still be significant.

"Herd immunity" is where so many people in a population are immune to the virus through vaccination or having caught it before that the chances of it spreading even among those who aren't immune is small.

But if, let's say, 20 per cent of the population refuses to be vaccinated, it's very hard to build up that herd immunity. The infection continues to circulate.

Politics and logistics?

Production, distribution and storage of a vaccine will not be easy in an Australian population of 25 million, let alone a global population of seven billion.

And there will be the question of who gets vaccinated first - the old and vulnerable? Health workers? The rich?

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The British scientific body, the Royal Society, has just brought out a report. The conclusions apply to Australia:

"Ethnic minority groups have been disproportionately impacted by the pandemic and overcoming barriers to vaccination will require culturally sensitive collaboration," the report said.

"Criteria for vaccine prioritisation should be defined and made explicit. There should be public dialogue and engagement to manage expectations and understanding of vaccine effectiveness, safety, side effects, availability and access."

This is all too gloomy

It may be.

Professor Esterman thinks that the chances of a vaccine are very high but it is not guaranteed.

"A vaccine would be fantastic but it won't take us back to life before COVID," he said.

But it would merit hats being thrown in the air. It may work imperfectly and have to be combined with other measures. There are now, for example, reasonably reliable, quick tests available. It may be that an initial vaccine plus better testing will give us a glimpse of that normality we yearn for.

Nobody knows when - but it won't be before the end of this year but may be before the end of next.

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This story Why a coronavirus vaccine won't be the magic bullet first appeared on The Canberra Times.

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