Why global eradication of Covid-19 is more feasible than polio

Eradicating Covid-19 across the globe is theoretically more feasible than it has been for polio, but much less so than it was for smallpox, according to an analysis by public health experts.

The researchers, writing in the international journal BMJ Global Health, ranked the feasibility of eradicating the three diseases based on technical, socio-political and economic factors.

Smallpox, which was declared eradicated in 1980, had the highest average score for eradication feasibility. It had an average score of 2.7 on a three-point scale across 17 variables. In comparison, Covid-19 had an average score of 1.6 and polio an average of 1.5.

Read more: Covid-19 during pregnancy increases risk of preterm birth: Lancet Study

Experts at the University of Otago in New Zealand defined elimination as the reduction to zero of the incidence of infection caused by a specific agent in a defined geographical area as a result of deliberate efforts; while eradication of infection would mean the permanent reduction to zero of the worldwide incidence of infection caused by a specific agent as a result of deliberate efforts.

The combination of vaccination programmes, public health measures and the global interest in combating Covid-19, all contribute to making eradication possible, according to Nick Wilson, Professor at the varsity.

"Elimination of Covid-19 at the country level has been achieved and sustained for long periods in various parts of the Asia Pacific region, which suggests that global eradication is possible," Wilson said, adding that the analysis puts eradicating Covid-19 into the realms of possibility in terms of technical feasibility.

Vaccination programmes have been responsible for the global eradication of smallpox and two of the three serotypes of poliovirus. Some other diseases are close to being eradicated without the use of vaccines, with China recently becoming the 40th country to be certified malaria-free.

While there has been a focus on the need to reach herd immunity to overcome Covid-19, population immunity may not be essential to combat the disease, with smallpox having been eradicated through ring-vaccination programmes that target the contacts of those infected, Wilson said.

The challenge of eradicating Covid-19 relative to smallpox and polio include poor vaccine acceptance in some countries and the emergence of variants of the pandemic virus that may be more transmissible or able to evade the protection from vaccines.

But, the virus will eventually reach the limit of its ability to mutate into more infectious forms, and new vaccines will likely be formulated to deal with evolving strains of the disease, Wilson said.

Other challenges include the high cost of vaccinating the world's population and upgrading health systems and achieving international cooperation in the face of aggressive anti-science movements and vaccine nationalism. While the pandemic virus may infect wild and domestic animal populations, this is unlikely to be a serious challenge to eradication.