Flu control has come a long way since 1918
Re: “Remember lessons from the Spanish flu epidemic,” letter, Jan 11. T he current upswing in influenza activity, and the seasonal push for vaccination, have attracted letters to the editor. The apparently poor performance of this year’s vaccine in protecting against the predominant strain is being legitimately taken as an opportunity to question our current approach and even the role of vaccines.
That the 1918 influenza pandemic, due to a novel strain of the virus, was among the deadliest in human history is highlighted by a letter-writer, who poses the question: “Are we more prepared now than they were then?”
As a public-health scientist, I would say emphatically that we are, but concur that our organizational preparedness and adequacy of flu-vaccine technology have much room for improvement. Nonetheless, there are historical, scientific and organizational reasons to consider that we have advanced considerably since 1918.
The so-called Spanish flu came on the heels of the First World War, which left many nations impoverished and malnourished, enhancing their vulnerability to any new pathogen. The quality and availability of medical care was marginal by our standards.
It is especially noteworthy that deaths during influenza epidemics are due mostly to complications, especially pneumonia. While some deaths are directly attributable to the virus, most are due to secondary bacterial infections, and in 1918, there were no antibiotics effective in treating any of these. Medical scientific knowledge was poor, and public-health measures ineffective; the death rate was high.
The isolation of the influenza virus in 1933 led promptly to the development of vaccines, initially live attenuated virus strains, then (in the 1940s) inactivated vaccines. Concurrently, it became evident that influenza viruses mutated, leading to almost continual changes. Major “shifts” sometimes caused epidemics, while less dramatic “drifts” in antigenic structure led to what we now term “seasonal influenza.”
By about 1970, many national laboratories around the world were encouraged to share information on newly emerging strains, and to correlate these with local morbidity and mortality estimates. Since 1973, the World Health Organization has been issuing annual recommendations for influenza-vaccine composition based on results from an evolved version of this surveillance system.
Clearly, for some years, vaccine formulation is on target for prevailing strains, while for other years, not so much. Average protective efficacy over recent years is estimated to be in the range of 40 to 60 per cent (although much lower for this year’s version).
These shortcomings duly acknowledged, an approximate 50 per cent reduction in disease burden is useful when viewed for a whole population, and certainly no such benefit was available in 1918.
The greatest challenges to our current approach are logistical and organizational. A decision must be made (using data from another part of the world) regarding the candidate virus(es) to select for the next round of vaccine production. After this commitment is made, production and distribution take time, yet must be done before the new strain begins to circulate with force in one’s own geographic region.
This leaves no time to evaluate the efficacy of vaccines in terms of preventing cases, so clinical trials are focused instead on immunological potency (potential for efficacy) and safety. Although an efficacy trial would be of value in principle, to await such results would mean that an epidemic would be well advanced before a decision to use the vaccine could be made.
The efficacy of influenza vaccines and the effectiveness of our influenza vaccination programs are therefore evaluated during and after the influenza season.
Science will solve the challenge of a virus that keeps changing its structure. Eventually, we will achieve a universal vaccine that does not depend on playing catch-up.
But for now, given our technology and organizational capacity, we are more prepared than they were in 1918.