A Dose of Realism on a COVID-19 Vaccine Strategy
A targeted immunisation programme may offer some protection, but it will not deliver ‘life as normal’.
For those holding on to hope of an imminent COVID-19 vaccine, news this weekend that the first could be rolled-out as early as ‘just after Christmas’ will have likely lifted spirits.
UK deputy chief medical officer Professor Jonathan Van-Tam reportedly told MPs a vaccine developed by Oxford University and AstraZeneca could be ready for deployment in January, while Sir Jeremy Farrar, Sage scientific advisory group member and a director of the Wellcome Trust, has said at least one of a portfolio of UK vaccines could be ready by spring.
Much has been written and said about how the world will return to normal when a vaccine is widely available. But that really won’t be true. It is important that we are realistic about what vaccines can and can’t do.
Vaccines protect individuals against disease and hopefully also against infection, but no vaccine is 100% effective.
To know what proportion of a community would be immune after a vaccination programme is a numbers game – we must multiply the proportion of a population vaccinated by how effective the vaccine is.
The UK currently has amongst the highest national coverage of flu vaccine in the world, vaccinating around 75 per cent of the over 65s against flu every year; most countries either do worse or have no vaccination programmes for older people. It is reasonable to expect that this level of coverage could be achieved for COVID-19 vaccine in that age group in the UK.
If the COVID-19 vaccine is 75 per cent effective – meaning 75 per cent of those vaccinated become immune – then we would actually only protect 56% of that target population (75 per cent x75 per cent). This would not be enough to stop the virus circulating.
Half of our highest risk group would remain susceptible, and we won’t know who they are. Relaxing social distancing rules when facing those risks seems a bit like Russian roulette.
Now let’s look at people younger than 65 in medical risk groups. In a good year, the UK vaccinates 50 per cent of them against flu. That means just over a third of them are going to be protected (50 per cent x 75 per cent).
Just to make matters worse, regulators such as the US Food and Drug Administration and the European Medicines Agency have said that they would accept a 50 per cent lower level for efficacy for candidate COVID-19 vaccines. If that efficacy level is fulfilled, we have to multiply coverage by 50 per cent efficacy, not 75 per cent, and suddenly it all gets more concerning.
As well as protecting individuals, vaccines can protect communities, through the interruption of transmission. One of the best examples comes from the UK meningitis C vaccination campaign of the late 1990s.
There was a 67 per cent reduction in the number of cases in the unvaccinated children and young people because they were being protected by their contacts who had been vaccinated and were no longer transmitting infection.
If we want to see population protection from COVID-19 vaccination, we are going to need high levels of protection (coverage x efficacy) across all ages, vaccinating not just the at-risk groups, as is being planned.
To stop transmission, we must vaccinate anyone who can transmit infection. Anything less means that our goal is only individual protection and not the interruption of transmission.
A recent announcement from the head of the UK Vaccine Task Force that the strategy will be targeted vaccination makes it abundantly clear that the UK vaccine strategy at the moment is not to try to interrupt transmission, despite having hundreds of millions of COVID-19 vaccine doses on contract. With less than 10 per cent of the population showing evidence of having been infected, targeted vaccination will not allow ‘life as previously usual’ to come about.
If countries do decide to switch from a personal protection policy to a transmission-interruption strategy, obstacles remain. Much will depend on the successful vaccination (probably with two doses) of people who have not previously seen themselves to be at elevated risk. The challenge will be persuading the young, for example, to be vaccinated, not for their own benefit, but for others.
The situation for developing countries will be even further away from achieving population immunity. The COVAX initiative (a global risk sharing and pooling vaccine arrangement) – proposes vaccines for just 3 per cent of population initially (for essential workers); followed by up to 20 per cent for the older and vulnerable.
Again, these quantities of vaccine will be seriously insufficient to have impacts on transmission. Even as industrialised nations struggle to interrupt transmission - ongoing transmission in any country threatens all countries.
Adherence to recommendations for any COVID-19 interventions – social distancing, lockdowns, home working, cancelled holidays or vaccinations, depend on trust. If politicians are telling us that the present impositions in our lives are only going to last until we have vaccines, then the reality is that a false hope is being promulgated.
Vaccines are probably the most powerful public health intervention available to us. But unless their benefits are communicated with realism, confidence in all recommendations will be put at risk.
While hope and optimism are much needed in these dark times, it is important to be transparent. We need to communicate the clear message that although targeted vaccination may offer some protection, it will not simply deliver ‘life as we used to know.’
This is a version of an article originally published in The Guardian.
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