World Polio Day: What you need to know about polio vaccines- how effective and safe is OPV?
Polio is a highly contagious disease caused by the poliovirus that attacks the central nervous system, leading to breathing problems, paralysis or even death in a matter of hours. World Polio Day, celebrated on October 24, aims to raise awareness and resources in support of effort towards polio eradication. On 27th March 2014, India was declared a polio-free country by the World Health Organisation (WHO). This milestone was hailed as a breakthrough for the country who once accounted for almost 70 per cent of all polio cases worldwide.
Ahead of the Silver Jubilee of the Pulse Polio Campaign on 31st October 2019, Union Health Minister Harsh Vardhan urged to renew the pledge to reach every single child to save them from a vaccine-preventable disease. He also thanked all stakeholders who contributed to the Polio Eradication programme, which was launched in 1994, while also adding that the best practices and systems established by the campaign have benefitted other health programmes.
Polio vaccines: Benefits and risks of OPV and IPV
There is no cure for polio but safe and effective vaccines can help prevent the disease. To prevent polio, people need to be vaccinated against all three types of poliovirus (WPV) – type 1, type 2, and type 3. The two vaccines used to protect against polio disease are – oral polio vaccine (OPV) and inactivated poliovirus vaccine (IPV).
Oral polio vaccine: According to the OPV is a mixture of live attenuated poliovirus strains of each of the three serotypes. However, after poliovirus type 2 was declared eradicated in 2015, trivalent OPV (which contains all three types of poliovirus) was replaced with bivalent OPV (contains only poliovirus type 1 and 3) – removing the type 2 component from immunisation programmes. This switch means OPV no longer protects against wild poliovirus 2.
The OPV drives have been attributed to the decline in polio cases worldwide. OPV, which is used in many countries, helped eliminated polio disease from India. However, some experts have raised concerns over the administration of OPV in the country, citing health risks.
In a recent analysis published in the T Jacob John, a top Indian Paediatrician and an emeritus Professor at Christian Medical College, Vellore, questioned the efficacy of OPV. The analysis jointly published with Mumbai-based Paediatrician Dhanya Dharmpalan stated that the choice of OPV as the tool for polio eradication was not a wise decision taking into account its failure to ensure safety and efficacy.
John, who has earlier advised the World Health Organisation and the Indian government on polio eradication policies, stressed that IPV, on the other hand, had been consistently shown to be completely safe and completely effective. The experts, in their analysis, stated that India must include a full immunising schedule of IPV in its Universal Immunisation Programme. Meanwhile, top officials in the Health Ministry argued that the benefits attached to OPV far outweighed the health risks.
The live vaccine virus has been highly effective at protecting against polio. But the OPV virus can accumulate changes over time and become like wild poliovirus in rare cases, as per the These new viruses, which are called vaccine-derived polioviruses (VDPV), can result in polio disease. The CDC notes that people who receive OPV may shed the virus and can infect those who are not vaccinated.
Inactivated polio vaccine: Some countries, including the US, have switched to IPV, which uses an inactive (dead) form of the virus that cannot cause polio disease. This means IPV can protect people against all three types of poliovirus with no risk of vaccine-associated polio. Since IPV does not contain any live virus, people receiving this vaccine do not shed the virus, which means they cannot infect others. The IPV vaccine is safe and very effective in preventing polio when all recommended doses are completed. No serious adverse reactions to this vaccine have been documented.
Currently, are given at ages 6 and 14 weeks in India, in lieu of the recommended one full dose intramuscular (IM) IPV at 14 weeks.