Friday, November 02, 2018

CDC: 2018 Interim Guidance On Allocating & Targeting Pandemic Influenza Vaccine


When the next influenza pandemic strikes, the overarching aim of the national pandemic influenza vaccination program is to:
  • `. . . . vaccinate all persons in the United States (U.S.) who choose to be vaccinated, prior to the peak of disease'
  • . . . . to have sufficient pandemic influenza vaccine available for an effective domestic response within four months of a pandemic declaration'
  • ` . . .  to have first doses available within 12 weeks of the President or the Secretary of Health and Human Services declaring a pandemic'
Given the logistical and scientific challenges, success is far from assured, but the HHS and other US agencies have invested a tremendous amount of money and effort into creating faster, more efficient vaccine manufacturing capabilities, and into the stockpiling of pre-pandemic vaccines.

The reality is, just about everything would have to go right for these laudable goals to be met. A few (of the many) barriers to success include:
  • A fast moving pandemic virus could sweep the globe in a matter of two or three months, peaking long before a vaccine could be deployed.
  • A new, or difficult to grow influenza subtype (or a non-influenza virus), could add months or even years to to vaccine development (see JAMA: Challenges Of Producing An Effective & Timely H7N9 Vaccine).
  • A severe enough pandemic could disrupt supply chains, further hampering the manufacture, and distribution, of any pandemic vaccine (see Supply Chain of Fools).
  • And, as we've seen with the seasonal H3N2 vaccine the past few years, and some sobering clinical trials on H7N9 and H5N1 vaccines, the high  effectiveness of a pandemic vaccine is not guaranteed.
It is therefore not only prudent, but essential, that the government decide how they will allocate limited pandemic vaccine supplies during a pandemic.  And as with any triage system, many difficult decisions are required.  
Last week, the CDC released an updated Pandemic Vaccine Targeting Guidance [400 KB, 25 Pages], which replaces the 2008  HHS Guidance on Allocating And Targeting Pandemic Influenza Vaccine.
From the Introduction, this new release includes:
Several new elements have been incorporated into the 2018 guidelines.
First, the guidance uses updated pandemic severity categories based on the current CDC Pandemic Severity Assessment Framework 1.
Second, the updated guidance incorporates lessons learned from the 2009 H1N1 pandemic response, such as the unpredictability of pandemic severity and timing, variability of the impact of pandemic severity on critical infrastructure functions, challenges with vaccine supply overall and variability among manufacturers, and the need for flexibility at the state, tribal, and local levels to best manage vaccine supplies to meet local needs.
Third, this document includes the consideration that two doses of vaccine and co-administration of adjuvant may be required to produce protective immunity in some scenarios.
Fourth, pharmacists and pharmacy technicians are included in Tier 1a, since pharmacists (and pharmacy technicians) will be crucial to antiviral dispensing and many pharmacists will be pandemic vaccine immunizers. 
Finally, the estimated numbers of population groups are based on 2015 U.S. Census population estimates
An overview of the tiered allocation system, based on pandemic severity, is shown in the chart below. The second chart shows a further refinement, dependent upon the quantity of vaccine that is available.

From the CDC's summary page:
The overarching objectives guiding vaccine allocation and use during a pandemic are to reduce the impact of the pandemic on health and minimize disruption to society and the economy.
Specifically, the targeting strategy aims to protect those who will: maintain homeland and national security, are essential to the pandemic response and provide care for persons who are ill, maintain essential community services, be at greater risk of infection due to their job, and those who are most medically vulnerable to severe illness such as young children and pregnant women.
There is a lot to review in this 25-page Guidance document, so you'll want to download it and read it in its entirety.

While most people fear falling ill from the virus during a pandemic, emergency planners know that there are even greater dangers.
A 1918-equivalent flu virus might claim 2 or 3 million American lives directly, but if it disrupts the delivery of essential services (health care, food, electricity, or water), millions more could die from collateral damage. 
This scenario was well presented in last May's Johns Hopkins day-long pandemic table top exercise (see CLADE X: Archived Video & Recap), which provides a sobering look at a plausible pandemic where hundreds of millions of people could die, many from indirect causes.
If you don't have the time to watch the entire 8 hour exercise, I would urge you to at least view the 5 minute wrap up video. It will give you some idea of the possible impact of a severe - but not necessarily `worst case' - pandemic.
Recap Video
Worth noting in this scenario, a safe and effective vaccine is thought `just around the corner', but fails to materialize in the first year.  As a result, health care systems, our infrastructure, and our economy descend into chaos.
Prepared or not, we'll have to deal with whatever comes down the pike. And while a vaccine will be vital to end a pandemic, the adoption of NPIs' - Non-pharmaceutical Interventions - will be critical to reduce the impact while we wait for its arrival (and for countries unlikely to see a vaccine anytime soon).

The CDC’s Nonpharmaceutical Interventions (NPIs) webpage defines NPIs as: 
Nonpharmaceutical interventions (NPIs) are actions, apart from getting vaccinated and taking medicine, that people and communities can take to help slow the spread of illnesses like influenza (flu). NPIs are also known as community mitigation strategies. 
Social distancing, staying home when sick, avoiding crowds, even the closure of schools or other public venues are all potential NPIs.

The CDC, and FEMA continue to urge pandemic preparedness, and in early 2017 the CDC updated their CDC/HHS Community Pandemic Mitigation Plan - 2017, which recognizes a vaccine could be months in coming, and focuses on reducing the spread of a pandemic virus through non-pharmaceutical interventions (see Community Pandemic Mitigation's Primary Goal : Flattening The Curve).

While telling people to wash their hands, cover their coughs, avoid crowds, and stay home while sick may seem like a weak response to a pandemic - until a vaccine becomes widely available - they (and other more disruptive measures like school closures, cancellation of public events, etc.) may end up being our most powerful weapons in a pandemic.