While the opening, and chaotic, first 9 months of the COVID-19 pandemic has focused primarily on hospital capacity, testing, and NPIs (social distancing, masks, etc.) the hope is that sometime in the next few months (one or more) safe and effective COVID vaccines will become available.
A major milestone to be sure, but to paraphrase Winston Churchill, more like the `end of the beginning than the beginning of the end'.
Developing a vaccine, and getting into the arms of billions of people, are two decidedly different tasks. And there is much we don't know about the production capacity, effectiveness, and duration of protection of any vaccine.
- The quantity of vaccine that can be produced and delivered in the first 12 months is unknown, but may be limited to two billion doses or less.
- It seems likely that most people will need two doses - spaced 21 to 28 days apart - and that not only increases the complexity of any vaccination program, it would also cut the number of people who can be protected in half.
- If a COVID-19 vaccine is anything like the flu vaccine, older adults - who are in greatest need of protection - may derive the least immunity.
- And their are growing concerns - based on a small number of reinfections - that vaccine induced immunity may be measured in months, not years.
Decisions on who gets the vaccine first will be announced only after crucial questions over manufacturing capacity, VE (vaccine effectiveness) in different age cohorts, and safety in children and other vulnerable populations are answered.
On Friday, the MRC Centre for Global Infectious Disease Analysis at Imperial College London released their 33rd report on COVID-19, this time centered on modelling the allocation and potential impact of a COVID-19 vaccine.
While all of the above questions remain unanswered, this 21-page report models and evaluates various scenarios, in hopes of covering the likely bases.
First, the link and summary from the report, followed by a link and excerpts from a Imperial College of London press release. You'll want to read the paper in its entirety. I'll have a postscript when you return.
Date: 25 September 2020
Alexandra B Hogan, Peter Winskill, Oliver J Watson, Patrick GT Walker, Charles Whittaker, Marc Baguelin1, David Haw, Alessandra Løchen, Katy A M Gaythorpe,Imperial College COVID-19 Response Team, Farzana Muhib, Peter Smith, Katharina Hauck, Neil M Ferguson, Azra C Ghani1
Several SARS-CoV-2 vaccine candidates are now in late-stage trials, with efficacy and safety results expected by the end of 2020. Even under optimistic scenarios for manufacture and delivery, the doses available in 2021 are likely to be limited.
Here we identify optimal vaccine allocation strategies within and between countries to maximise health (avert deaths) under constraints on dose supply. We extended an existing mathematical model of SARS-CoV-2 transmission across different country settings to model the public health impact of potential vaccines, using a range of target product profiles developed by the World Health Organization. We show that as supply increases, vaccines that reduce or block infection – and thus transmission – in addition to preventing disease have a greater impact than those that prevent disease alone, due to the indirect protection provided to high-risk groups.
We further demonstrate that the health impact of vaccination will depend on the cumulative infection incidence in the population when vaccination begins, the duration of any naturally acquired immunity, the likely trajectory of the epidemic in 2021 and the level of healthcare available to effectively treat those with disease. Within a country, we find that for a limited supply (doses for <20% of the population) the optimal strategy is to target the elderly and other high-risk groups.
However, if a larger supply is available, the optimal strategy switches to targeting key transmitters (i.e. the working age population and potentially children) to indirectly protect the elderly and vulnerable. Given the likely global dose supply in 2021 (2 billion doses with a two-dose vaccine), we find that a strategy in which doses are allocated to countries in proportion to their population size is close to optimal in averting deaths. Such a strategy also aligns with the ethical principles agreed in pandemic preparedness planning.
COVID-19 vaccine may not need to be fully effective to benefit public health
by Dr Sabine L. van Elsland, Stephen Johns
25 September 2020
Even an imperfect, partially effective vaccine against COVID-19 could have a substantial public health benefit if rolled out in 2021, a report says.Researchers from Imperial's COVID-19 Response Team also found that the optimal approach to allocating vaccine doses within a country will require a detailed understanding of the local setting – including relevant risk groups and the stage and spread of the epidemic.With limited supply, this might involve targeting elderly and other high-risk groups. With larger supply available to a country, a more efficient strategy would be to vaccinate the working-age population.The researchers found that as supply increases, vaccines that reduce or block infection – and thus transmission – in addition to preventing disease have a substantial greater impact than those that prevent disease alone, due to the indirect protection provided to high-risk groups.Global allocationEven under optimistic scenarios for manufacture and delivery, the doses available in 2021 are likely to be limited. In this report, researchers explore the impact of vaccine allocation within countries and between countries to maximise health and avert deaths under constraints on dose supply.Allocating the limited doses likely to be available in 2021 to countries according to their population size is almost as efficient as more nuanced strategies. Such a strategy also aligns with the ethical principles agreed in pandemic preparedness planning. Defining the “optimal” strategy ahead of time is challenging because it is sensitive to vaccine characteristics that will not be fully known at the time of roll-out.Global public health value of the vaccine can be maximised by ensuring equitable access: acting collectively in this way during the early stages of vaccine deployment remains the ethical approach to take, even if this is not the most beneficial short-term strategy from a national perspective, according to this report.
After a summer filled with `Forward Looking' & `Aspirational' Vaccine Press Releases, we are starting to get a badly needed reality check on the likely impact of having a COVID-19 vaccine `in early 2021'.
Hopes that a vaccine will - within a few months - return us back to `normal' are unrealistic, even if everything goes perfectly. A vaccine will help, certainly, but there is a long road ahead and we may be dealing with COVID-19 for years to come.
Of course, no one wants to hear this, anymore than they wanted to hear a year ago that a pandemic was inevitable (see Sept 2019's WHO/World Bank GPMB Pandemic Report : `A World At Risk') and that a coronavirus was a likely threat (see The JHCHS #Event201 (Fictional) CAPS Pandemic Scenario).But ready or not, the next pandemic virus is probably already out there - residing in a bird, a pig, a camel, or a bat - evolving inexorably towards human adaptation. If we get lucky, it will wait until we are clear of our current COVID threat before it emerges.
But we need to prepare as if it it could come tomorrow, as there are no guarantees in life.