#18,396
Although there are no guarantees that avian H5N1 will spark the next pandemic, it is a pretty good bet that the next pandemic will be caused by a novel `flu-like' virus (with influenza and coronaviruses being at the top of that list).While once thought of as a `once-in-a-generation' event, in my lifetime I've already experienced 4 legitimate pandemics (1957, 1968, 2009, 2020), 2 pseudo-pandemics (1977, 2003), and one `near-miss ' (1976).
Recent studies looking at avian H5 have raised concerns over the effectiveness of current antivirals, and there are a great many barriers to rapidly producing, and distributing, a novel flu vaccine.As Maggie Fox explained last year in SCI AM - A Bird Flu Vaccine Might Come Too Late to Save Us from H5N1, our options during the opening months of any pandemic will be limited. Unpopular as they might be, NPIs (non-pharmaceutical interventions like masks, social distancing, etc.) will once again become our first line of defense.
The rub with any new vaccine is that they tend to arrive late into a pandemic, after most people have already been exposed. They can certainly be useful for dealing with a `second wave', but they are unlikely to blunt the impact of the opening months.
It might be possible to shave weeks, or even months, off the delivery time of a pandemic vaccine if an older CVV (Candidate Vaccine Virus) were used instead waiting to isolate a new strain, but it might prove far less effective.
Which brings us the question: is it better to have a less-well-matched vaccine earlier (at 3 months), or wait (6 months or more) for a well-matched vaccine?
It is not an easy question to answer, because there are so many unknown variables. As the old saying goes, `If you've seen one pandemic . . . . you've seen one pandemic'. The speed of transmission (R0), its place of origin, its virulence (CFR and Attack Rate), and even its impact on different age groups, all change the outcome.
We've a study today that attempts to model the impact of early vs. late vaccination in a variety of pandemic scenarios, juggling virulence (moderate or severe), and vaccine effectiveness (high, moderate, or low), in order to try to quantify the probable benefits.
In order to keep all of this manageable the authors had to make a number of assumptions that may, or may not, hold true in the next pandemic; an origin in the Southern Hemisphere, a greater impact on older patients, and a single wave, etc.
While the full report is well worth reading in its entirety, the take-away is that it is better to have a less-well-matched vaccine available early, than a well-matched vaccine late. Follow the link to read the full report.
I'll have a postscript when you return.
npj Vaccines volume 10, Article number: 62 (2025) Cite this article
Abstract
We modeled the impact of initiating one-dose influenza vaccination at 3 months vs 6 months after declaration of a pandemic over a 1-year timeframe in the US population. Three vaccine effectiveness (VE) and two pandemic severity levels were considered, using an epidemic curve based on typical seasonal influenza epidemics.
Vaccination from 3 months with a high, moderate, or low effectiveness vaccine would prevent ~95%, 84%, or 38% deaths post-vaccination, respectively, compared with 21%, 18%, and 8%, respectively following vaccination at 6 months, irrespective of pandemic severity.
While the pandemic curve would not be flattened from vaccination from 6 months, a moderate/high effectiveness vaccine could flatten the curve if administered from 3 months.
Overall, speed of initiating a vaccination campaign is more important than VE in reducing the health impacts of an influenza pandemic. Preparedness strategies may be able to minimize future pandemic impacts by prioritizing rapid vaccine roll-out.(SNIP)
Discussion
Our analysis shows that the speed of vaccination is key to reducing the impact of an influenza pandemic. Even with a low effectiveness vaccine, initiating vaccination 3 months after the declaration of a pandemic would lower the disease burden compared with initiating a higher effectiveness vaccine at 6 months, with 23–94% incremental benefits across health outcomes and VEs.
While moderately and highly effective vaccines could flatten the pandemic curve if administered from 3 months, none of the scenarios evaluated could flatten the curve if administered from 6 months. Acute and ICU bed availability would also be less constrained under the early vaccination scenario, particularly with higher effectiveness vaccines, but administration of a vaccine at 6 months would not be able to prevent a surge in demand above bed availability thresholds in a severe pandemic, irrespective of VE.
(SNIP)
In summary, our analysis has demonstrated the importance of rapid initiation of mass vaccination during a future influenza pandemic, with speed of vaccination playing a more important role than VE on population-level health outcomes.
Preparedness exercises such as stockpiling potential pre-pandemic vaccines, as well as pre-emptive collection of data from newer vaccine manufacturing platforms, such as mRNA vaccines, will be paramount for ensuring a rapid and effective response in a future influenza pandemic.(Continue . . . )
This study uses a lot of epidemiological assumptions, which may (or may not) be a good fit for the next pandemic. Much will also depend upon how society reacts to the next pandemic.
- Will lockdowns be tolerated, or will people refuse masks and social distancing?
- Assuming a vaccine could be produced in quantity in 3 months, would large segments of the public actually embrace it? How much extra resistance against an mRNA vaccine?
- How much tolerance would the public have for (real or imagined) vaccine side effects, particularly in a low VE jab?
