Candidate polio vaccines are safe and immunogenic

The Lancet reports on a unique polio studio by the University of Antwerp

Findings from the first-in-human study of a new polio vaccine – novel oral polio vaccine, or nOPV – reported in The Lancet this week are promising. If subsequent studies are successful, such a vaccine has the potential to supplement current eradication efforts and sustain eradication of all types of polioviruses for the long-term.  

In 2017, the Centre for the Evaluation of Vaccination, Vaccine and Infectious Disease Institute (CEV) at the University of Antwerp tested two candidate polio vaccines in the container village of ‘Poliopolis.” As part of the study, two groups, each consisting of 15 volunteers, spent 28 days in complete quarantine. Results indicate that the two vaccines can be considered safe and immunogenic, and subsequent studies are underway to generate additional data on the candidate vaccines from larger populations and different age groups.

A new polio vaccine

While the world has made significant progress toward ending polio in the last 30 years, circulating vaccine-derived poliovirus (cVPDV) has emerged as a key challenge in the final stage of eradication efforts. ‘The oral vaccine that is currently in use has stopped the disease in most countries’, notes Professor Pierre Van Damme of the Centre for the Evaluation of Vaccination, Vaccine and Infectious Disease Institute (University of Antwerp). ‘However, in rare circumstances in settings of low immunization coverage, that oral vaccine can revert to cause paralysis. The new oral vaccine, expected to be more genetically stable than the current OPV and thus less likely to revert to the virulent strain, is advancing through successive clinical trials. If found to be effective, it could be used as early as in 2020 to prevent further cases of vaccine-derive polio’.

A global consortium of researchers, supported by the Bill & Melinda Gates Foundation, developed the new candidate vaccines, which are manufactured by BioFarma (Indonesia). The lead scientists of this consortium included Andrew Macadam (NIBSC, UK), Raul Andino (UCSF, USA) and Jennifer Anstadt, Cara Burns and Olen Kew from the US Centers for Disease Control and Prevention, the study’s primary lab partner. Several other global experts and organizations, including PATH, played an important role in successful implementation of this unique study.

No major side effects

As concluded in The Lancet, the study proceeded smoothly. ‘The two vaccines were tolerated well, with no significant side effects. Both of them resulted in a measurable immune response, with the generation of the necessary neutralising antibodies and seroconversion after vaccination’, explains Van Damme. ‘The vaccine virus was detectable in the stools of 15/15 (100%) and 13/15 (86.7%) of the volunteer participants. Reversion to neurovirulence was very low for the vaccine viruses that were isolated in the stools of the volunteers. Sequencing of the vaccine virus that was shed in the stool did not exhibit any loss of attenuation in relevant areas of viral genome in either of the candidate vaccines’.

Global partnership

The results of the first-in-human study are thus promising. Two follow-up studies on the candidate vaccines are now under way. The CEV has collaborated with colleagues from Ghent University to test the vaccines on 232 healthy adults between 18 and 50 years of age, Van Damme noted. In addition, based on the encouraging results from studies in Belgium, a clinical trial in young children and infants  in Panama is also getting closer to completion. The clinical evidence base generated by these series of clinical trials is expected to inform the use of nOPV for vaccine-derived outbreaks in near future.  Dr. Ananda S. Bandyopadhyay, Senior Program Officer from the Gates Foundation notes, ‘Thanks to a remarkable collaboration across geographies, and among pre-clinical and clinical investigators, vaccine manufacturers, global partners, and other stakeholders, clinical development of the first new oral polio vaccine in over sixty years is moving rapidly forward. If successful, this vaccine would further strengthen the chances of achieving and sustaining a world free of paralysis from all types of polioviruses.’