The current pandemic is a tough reminder that modern society remains vulnerable to emerging infectious diseases. Given that many long-known pathogens are now vaccine-preventable, the challenge in coming decades is to develop vaccines that protect us against future disease threats.
Disease outbreaks are inevitable
Time and again, diseases jump from animals to humans. COVID-19 is the third serious spillover of a coronavirus from bats into humans in the past 20 years, it follows SARS-1 in 2003 and the emergence of MERS in 2012. Wild and domestic animal populations provide an enormous reservoir where pathogens circulate and evolve new mechanisms to infect and spread to new hosts, including humans. It is not possible to prevent the emergence of pathogens into the human population, but good preparation will allow us to contain most outbreaks before they develop to epidemic or even pandemic levels.
Epidemic preparedness includes three essential activities: first, identify emerging infectious diseases (surveillance and monitoring); second, study these pathogens and third, preemptive vaccine development.
Mostly we fail at this third point, and there are good reasons for this: The development of a vaccine from the initial design through to completion of clinical trials may take upwards of a decade and cost over US$500 million. The risk of failure is high. Finally, when an effective vaccine is developed, it has little chance of commercial success because a relatively small number of doses will be sufficient to end an outbreak. The unfortunate result is that these projects are rarely brought to completion.
Lessons learned from Ebola and SARS-1
A tragic example is the Ebola vaccine. Despite more than 10 years of development, the vaccine was not ready for deployment until a year into the 2014 outbreak in West Africa. 11'000 people died in that outbreak and we now know that the vaccine provides 100% protection against the disease.
Similarly, in the case of SARS-1, the financial incentives to develop a vaccine dried up after public health measures brought that outbreak under control. Laboratory studies published in April this year indicated that a SARS-1 vaccine could have provided some protection against COVID-19 infection1. If development had continued, a SARS-1 vaccine would have been tested in the early stages of the COVID-19 outbreak and may have halted the course of this pandemic.
