The global eradication of COVID-19 is more feasible than it is for polio, but considerably less so than it was for smallpox, according to an analysis published in the journal BMJ Global Health on Tuesday.

Public health experts from the University of Otago Wellington in New Zealand noted that vaccination, public health measures, and global interest in achieving this goal all make eradication of COVID-19 possible.

However, they said, the main challenges lie in securing sufficiently high vaccine coverage and respond quickly enough to immune-escape variants of SARS-CoV-2, the virus that causes COVID-19.

The authors estimated the feasibility of COVID-19 eradication, defined as ''the permanent reduction to zero of the worldwide incidence of infection caused by a specific agent as a result of deliberate efforts''.

They compared it with two other viral scourges for which vaccines were or are available -- smallpox and polio -- using an array of technical, sociopolitical, and economic factors that are likely to help achieve this goal.

The authors used a three point scoring system for each of 17 variables such as the availability of a safe and effective vaccine, lifelong immunity, impact of public health measures, and effective government management of infection control messaging among others.

The average scores in the analysis added up to 2.7 for smallpox, 1.6 for COVID-19, and 1.5 for polio, they said.

Smallpox was declared eradicated in 1980 and two out of the three serotypes of poliovirus have also been eradicated globally.

"While our analysis is a preliminary effort, with various subjective components, it does seem to put COVID-19 eradicability into the realms of being possible, especially in terms of technical feasibility," the authors wrote in the study.

They acknowledge that relative to smallpox and polio, the technical challenges of COVID-19 eradication include poor vaccine acceptance, and the emergence of more highly transmissible variants that may evade immunity, potentially outrunning global vaccination programmes.

"Nevertheless, there are of course limits to viral evolution, so we can expect the virus to eventually reach peak fitness, and new vaccines can be formulated," the authors explained.

"Other challenges would be the high upfront costs for vaccination and upgrading health systems, and achieving the necessary international cooperation in the face of ''vaccine nationalism'' and government-mediated ''antiscience aggression''," they added.

The researchers also suggest that the persistence of the virus in animal reservoirs may also thwart eradication efforts, adding, however, this does not appear to be a serious issue.

They noted, on the other hand, there is a global will to tackle the infection.

The massive scale of the health, social and economic impacts of COVID-19 in most of the world has generated "unprecedented global interest in disease control and massive investment in vaccination against the pandemic," the authors said.

Unlike smallpox and polio, they said, COVID-19 also benefits from the added impact of public health measures, such as border controls, social distancing, contact tracing and mask wearing, which can be very effective if deployed well.
"Collectively these factors might mean that an ''expected value'' analysis could ultimately estimate that the benefits outweigh the costs, even if eradication takes many years and has a significant risk of failure," the authors added.