Kolkata, Feb 10 (PTI) Oral polio vaccines (OPVs) are safe, effective and central to global eradication efforts, but there is a need for improved immunisation to combat the emergence of vaccine-derived
poliovirus strains, a US-based public health expert said.
Referring to India’s current status, Gates Foundation Deputy Director Dr Ananda Sankar Bandyopadhyay said paralytic outbreaks from circulating strains of variant polioviruses have not been detected in recent years, an indication that the country has been able to “maintain high routine immunisation coverage”.
Notably, India was certified polio-free in March 2014.
“Oral polio vaccines (OPVs) are safe, effective, affordable, and easy to deliver. Use of OPV through routine immunisation and mass vaccination campaigns has eliminated poliovirus transmission and prevented paralysis in children across the world, with 99.9 per cent of the world polio-free,” Bandyopadhyay told PTI from Seattle, USA.
He said variant strains primarily emerge in areas with weak immunisation coverage.
“In areas with persistently poor immunisation coverage, variant strains can emerge, primarily through viral recombination events between OPV strains and other enteroviruses in inadequately vaccinated communities. Thus, the solution to variant polio strains is improved vaccination coverage,” Bandyopadhyay said.
A vaccine-derived poliovirus (VDPV) is a strain related to the weakened live poliovirus contained in OPV.
Highlighting advances in vaccine technology, the health expert said, “With large-scale introduction of innovative tools such as the novel oral polio vaccine type 2 (nOPV2) that has now been rolled out for outbreak response in more than 40 countries, the risk of variants has been reduced further.” He also said optimal use of inactivated polio vaccine (IPV) alongside OPVs could “close immunity gaps, minimise risks of variant strains, and bring us closer to eradication”.
“It should be noted that paralytic outbreaks from circulating strains of variant polioviruses have not been detected in India in recent years, an indication that the country has been able to maintain high routine immunisation coverage with IPV and bOPV (bivalent oral polio vaccine), supplemented by national immunisation days with bOPV.” He asserted that the polio eradication programme builds on a strong network of surveillance to track and report trends of virus transmission and also monitors adverse events, which are “very rare”.
While acknowledging a global decline in vaccine acceptance in recent years, he said community participation remains critical.
“While the world has seen a decrease in the acceptance of all vaccines worldwide in the last 5 years, in most places, parents seek out lifesaving vaccines, including polio,” he said.
Participation and willingness of the communities have been and will continue to be essential to getting children vaccinated to secure a polio-free, paralysis-free future.
“We are heartened to see so much community support to protect future generations,” he added.
Explaining why polio eradication took longer than expected despite India’s eventual success, Bandyopadhyay said, “Polio is one of the most infectious viruses known, with its propensity to spread likely second only to measles, especially in settings with poor sanitation, lack of access to clean water, and less consistent hand hygiene.” A diverse and populous country like India had to overcome many hurdles, such as difficult-to-reach geographies, high population density, and population movement across the country for seasonal employment, to achieve its historic polio-free status, he said.
On the sustainability of India’s polio-free status amid concerns over declining routine immunisation and competing public health priorities, he said, “A decade and a half of being polio-free as demonstrated through a sensitive surveillance system indicates the country can sustain high immunisation coverage across different sub-populations.” “Protecting children, through generations, against the devastating impact of polio and the risk of life-long paralysis should remain a high priority everywhere, including in India,” he said, noting that the country has also introduced vaccines to protect children from pneumonia and severe diarrhoea.
Responding to scepticism on whether global eradication is realistic, Dr Bandyopadhyay said India’s experience demonstrated that the goal is achievable.
“India’s success in ending polio and maintaining polio-free status were decisive and sustainable achievement, thanks to the efforts of hundreds of thousands of dedicated individuals, including frontline healthcare workers,” he said.
“It set a shining example for other countries and continues to be regarded as a major global health milestone,” Bandyopadhyay added.
“Eradication remains a challenging goal, but a goal that can be, and must be, achieved. We have the tools to end polio everywhere, and with sustained global, regional and local commitment, we are closer than ever to eradicating the second human disease, once and for all,” he said.
Smallpox was the first human disease to be eradicated, while polio is all set to be the second one to follow it, Bandyopadhyay said before signing off. PTI SCH BDC
