Unethical to continue using polio-causing oral polio vaccines

Subject : Science

Section: Health

Context:

In 1988, the World Health Assembly declared WHO’s commitment to global eradication of polio by 2000. But in 1993, the goalpost was shifted — the goal was to eradicate only wild poliovirus globally by 2000.

Details:

That meant that eradicating vaccine-derived poliovirus (VDPV) and vaccine-associated paralytic poliomyelitis (VAPP) was no longer the objective.
The reason: developing countries using oral polio vaccine reported many vaccine-derived or vaccine-associated polio cases annually.
Meanwhile, the developed countries switched to inactivated polio vaccine thus eradicating polio decades ago.

Polio virus cases in India:

Though the last case of type 2 wild poliovirus was reported in October 1999 from India (and declared eradicated globally in 2015), more than 90% of vaccine-derived poliovirus outbreaks are due to type 2 virus present in oral polio vaccines.
Also, 40% of VAPP are caused by type 2 oral polio vaccine.
Similarly, the last case of type 3 wild poliovirus was reported in November 2012 (and declared eradicated in 2019).

Shift from trivalent to bivalent vaccine:

With type 2 wild poliovirus being eradicated and all type 2 polio cases being vaccine-derived, there was a global switch from trivalent (containing all three variants) to bivalent (type 1 and type 3) oral polio vaccine in 2016 to prevent any more type 2 vaccine-derived poliovirus.
The number of vaccine-derived type 2 poliovirus outbreaks have only increased sharply after the global switch to bivalent oral polio vaccine.

Concern over the Type-3 polio virus:

But many cases of VAPP from type 3 virus occur in countries using oral polio vaccine.
The Global Polio Eradication Initiative (GPEI) has never reported VAPP cases throughout the 34 years of polio eradication efforts. And the Indian government does not count VAPP as polio as such cases are sporadic and pose little or no threat to others.
In result, the number of VAPP-compatible cases showed an increasing trend in India from 1998 to 2013, so much so that they outnumbered the polio cases caused by wild poliovirus since 2004.
VAPP cases occur at a frequency of two-four cases per million birth cohort per year in countries that use OPV.
Based on this incidence rate, an estimated 50-100 children might suffer from VAPP every year in India.

Type 2 novel OPV:

A type 2 novel oral polio vaccine (OPV) that is genetically modified such that it is to less likely to revert to neurovirulence unlike the Sabin vaccine and therefore cause less type 2 vaccine-derived poliovirus cases was authorised by WHO under Emergency Use Listing in November 2020 and first used in the field in March 2021.
But as of May 2023, the novel vaccine, which is to be used only in type 2 VDPV outbreak situations, has already caused three type 2 VDPV cases.
However, the type 2 novel OPV vaccine does not address VAPP cases arising from continued use of oral polio vaccine.

Polio virus:

Polio is a crippling and potentially deadly viral infectious disease that affects the nervous system.
There are three individual and immunologically distinct wild poliovirus strains:
- Wild Poliovirus type 1 (WPV1)
- Wild Poliovirus type 2 (WPV2)
- Wild Poliovirus type 3 (WPV3)
Symptomatically, all three strains are identical, in that they cause irreversible paralysis or even death. However, there are genetic and virological differences, which make these three strains separate viruses which must each be eradicated individually.
The virus is transmitted person-to-person mainly through the faecal-oral route or, less frequently, by a common vehicle (for example, through contaminated water or food).

Vaccines:

Oral Polio Vaccine (OPV): It is given orally as a birth dose for institutional deliveries, then primary three doses at 6, 10 and 14 weeks and one booster dose at 16-24 months of age.
Injectable Polio Vaccine (IPV): It is introduced as an additional dose along with the 3rd dose of DPT (Diphtheria, Pertussis and Tetanus) under the Universal Immunisation Programme (UIP).

Initiative by India:

Pulse Polio Programme:
- It was started with an objective of achieving 100% coverage under Oral Polio Vaccine.
Intensified Mission Indradhanush 2.0:
- It was a nationwide immunisation drive to mark the 25 years of Pulse polio programme (2019-20).
Universal Immunization Programme (UIP):
- It was launched in 1985 with the modification to ‘Expanded Programme of Immunization (EPI). The objectives of the Programme include:
- Rapidly increasing immunization coverage
- Improving the quality of services
- Establishing a reliable cold chain system to the health facility level
- Introducing a district-wise system for monitoring of performance
- Achieving self-sufficiency in vaccine production.

Global Polio Eradication Initiative:

It was launched in 1988 by the Global Polio Eradication Initiative (GPEI), by national governments and WHO. Presently, 80% of the world’s population is now living in certified polio-free regions.
An estimated 1.5 million childhood deaths have been prevented, through the systemic administration of vitamin A during polio immunization activities.