A vaccine against Covid-19: Is it too early to celebrate?

There are still many questions that need to be answered about how inoculation would work

 The new Covid-19 vaccine produced by BioNTech and Pfizer is based on a totally new principle. Photograph: BioNTech/EPA

The new Covid-19 vaccine produced by BioNTech and Pfizer is based on a totally new principle. Photograph: BioNTech/EPA


Hallelujah! It looks like we might actually have a successful vaccine against Covid-19 in 2021. The news from Pfizer and the German company BioNTech has lifted spirits across the globe – as well as stock markets everywhere – and any plans for a quiet Christmas will be difficult to implement.

Early indications from the Pfizer and BioNTech ongoing Phase 3 trial are that one of their vaccine options is performing with 90 per cent efficacy. This means that 90 per cent of people who received the vaccine did not become infected when exposed to the virus. If that rate were to be maintained to trial completion, it would surpass the most optimistic views of many immunologists and public health doctors.

From early in the pandemic, scientists and doctors were dubious that a successful vaccine could be made against Covid-19 in a short timeframe. Why? First of all, making any vaccine that successfully blocks viral infection is difficult – we actually only have about 20.

Why is it so difficult? It turns out that the immune system is very complex: it is made up of dozens of cell types and 100s of molecules, many of which function differently and in different combinations depending on the organ they inhabit in the body. To complicate matters further, it turns out that viruses are unbelievably wily; they have evolved multiple different ways of blocking immune cells and molecules, so they fail to function properly.

So it is still virtually impossible to know what combination of immune mechanisms will protect against any one species of virus. To make matters worse, we now know that humans can respond very differently to vaccination, so what works in one type of person might not work in another; it usually takes years to find out if a new vaccine will protect everyone.

For all these reasons and more, rational design of effective vaccines is still a distant dream and plain good luck has played a key role in the discovery of the few successful vaccines we have today. These are mostly variations of the pathogens themselves that have been treated so they no longer infect people but can still stimulate a protective immune response.

The new Covid-19 vaccine is based on a totally new principle, which further confounded any optimism that it might work. The scientists in BioNTech developed a process for packaging a small portion of the Covid-19 nucleic acid – which contains its unique genetic information – in such a way that, when injected, it would be taken up by specialised immune cells in the body. The molecular machinery inside these immune cells generates the viral protein coded for by the viral nucleic acid, which then stimulates an immune response. To date, no successful vaccine has been made using this approach.

However, all news, even good news, comes with unknowns and questions to be answered. First of all, why did Pfizer release this information before completion of their trial? At the moment, we only know that the vaccine is protective 28 days after administration of the first shot (of a two-dose schedule). How long will the protection last? Will all types of people be protected? What about people with co-morbidities? What about people who are overweight? The study has not yet reached its target (it is due to be halted when 160 people have become infected) and so has not been written up in a formal paper, submitted to a journal and undergone peer-review.

Has it been performed as rigorously as we would like? Have any shortcuts been taken? The initial results have been reported so early in the trial, it is unlikely that the 90 per cent efficacy will be maintained. Was news of this particular vaccine success released early because there were rumours that data from other vaccine trials might be equally exciting?

Even if the news about this vaccine continues to be good, enormous obstacles will have to be overcome before we can be sure a Covid-19 immunisation programme will actually rid the planet of the virus, just as small pox vaccination got rid of the variola virus. For this to happen, enough people must be made immune to Covid-19 so that the virus cannot survive in the population and we achieve herd immunity. The logistics of making enough vaccine of high quality for a global immunisation programme are significant.

Distribution of a vaccine that requires being held at minus 70 to 80 degrees presents more obvious problems (though seemingly solutions are already being proposed which involve specially designed cases that can hold “dry ice”/solid carbon dioxide). Then, where should the vaccine be administered and by whom? (It requires two doses by injection which of course requires special expertise and equipment).

These are all practical matters that don’t even begin to address the ethical issues that surround delivery of any new vaccine during a pandemic. Who should receive the first doses of vaccine when they become available? Should the first in line be healthcare workers? The most vulnerable? The old? The poor? Children? Who should pay for it? Should all countries pay the same? Should poorer countries be subsidised?

What about personal freedom and people for whom the choice not to be vaccinated comes before societal good and the communal effort to rid the planet of the virus? A recent survey by Ipsos MRBI for the Irish Pharmaceutical Healthcare Association (IPHA) found that 12 per cent of respondents would not take a vaccine while 33 per cent were said they were unsure. If vaccine hesitancy remains at this level, we may not achieve herd immunity; what do we do then? Do we want to live in a society where we continue to be at risk of infection despite an effective vaccine? Can we insist that our doctor is vaccinated? Our bus driver? Our dentist? Our children’s teachers? Everybody on our plane? Will we have to make sure that mass testing continues for years so that we can keep track of where the virus is?

As ever, we need more studies, more data, more analysis, more interpretation. It is wonderful news that there are many promising vaccine candidates in the pipeline and undergoing trials. We need to hear more about these. It is clear that any national vaccine preparedness strategy will need major discussion if it is to get buy-in from us all. So let’s hear what is being planned and let’s talk about it – while we celebrate – a bit.

Cliona O’Farrelly is Professor of Comparative Immunology at Trinity College Dublin

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