The World Health Organisation (WHO) Strategic Advisory Group of Experts on Immunisation (SAGE) has endorsed two groundbreaking vaccination strategies to accelerate the global eradication of Polio.
The announcement was made during SAGE's recent meeting in Geneva, focusing on the use of fractional doses of inactivated polio vaccine (IPV).
The experts also discussed the release of novel oral vaccines to overcome persistent barriers in the final stages of the decades-long eradication campaign.
SAGE suggests that fractional doses of Sabin-based IPV will work the same way as rational doses of Salk-based IPV. By following this approach, one-fifth of a standard vaccine dose is injected intradermally instead of intramuscular injection, stretching limited vaccine supplies.
SAGE emphasised that by using this approach, vaccine supply could be stretched and "reach more children,” especially crucial in resource-constrained settings where access to full doses remains challenging.
The science of this approach is proven. A study published in BMC Global Public Health confirms that a portion of the IPV dose contains all three categories of polio vaccine, and with this, infection by all polioviruses is prevented.
Numerous trials have demonstrated that two half-doses administered intradermally result in a significantly higher degree of immune response compared to one full dose administered intramuscularly, with no adverse effects becoming more pronounced.
SAGE also supported the broader introduction of new oral polio vaccine type 2 (nOPV2), specifically to address endemic outbreaks of circulating variant poliovirus type 2 (cVDPV2).
This new vaccine offers the same protection as previous oral vaccines, but with a significantly lower risk of genetic reversion to a form capable of causing paralysis—a significant development in the response to outbreaks.
Recent surveillance data highlight the urgency of the situation: Pakistan reported three cases of wild poliovirus last week, and other countries (Nigeria, Benin, Papua New Guinea and others) reported several cases of cVDPV2 and positive environmental samples.
Those outbreaks are primarily in areas with permanent immunisation weaknesses, where the new tools would be crucial.
While endorsing these technical innovations, SAGE delivered a sovereign message about the limitations of medical interventions alone.
The group stated, “SAGE strongly emphasised that polio eradication can’t be achieved solely through technical interventions”, pointing towards the ongoing wild poliovirus transmission in Pakistan and Afghanistan.
The final element, according to SAGE, is enduring national political leadership and accountability at all levels, as it improves coverage of routine immunisation, vaccination campaigns, surveillance, and outbreak response, but finds that these efforts all rely on political will.
The effects of these methods are seen in Somalia. Health authorities reported excellent coverage results with the use of fractional IPV during pilot campaigns in five districts in 2021.
The campaigns themselves were organised by the Somali Ministry of Health, with the assistance of UNICEF and WHO. They demonstrated good community acceptance and confidence in the new way of delivery.
Since its foundation, the international campaign against Polio has been a remarkable success, with the number of new cases this year decreasing to only 22 per year, compared to 350,000 in 1988.
However, the ongoing difficulties in the last remaining transmission reservoirs would necessitate something new.
The support of fractional dosing and new oral vaccines is the most recent development in what has already brought the world to the edge of eradicating only the second disease in human history, providing a new reason to believe that the final mile of a long, decades-long journey may at last be within reach.