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Sabin-IPV produces VAPP protection comparable with Salk-IPV
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A Sabin strain-based inactivated poliovirus vaccine administered to Chinese infants rendered an immune response against vaccine-associated paralytic poliomyelitis that was comparable to Salk inactivated poliovirus vaccine, according to recently published study findings.
“A Sabin strain-based inactivated poliovirus vaccine (Sabin-IPV, Pfizer) is recommended for use in developing countries and regions based upon considerations such as replacing OPV by IPV to decrease and eliminate [vaccine-associated paralytic poliomyelitis (VAPP)],” Guoyang Liao, PhD, from the Institute of Medical Biology at Chinese Academy of Medical Science and Peking Union Medical College, and colleagues wrote. “However, the greatest concern related to switching from a live to an inactivated vaccine is whether effective immunogenicity can be ensured with the inactivation process.”
Liao and colleagues conducted a double masked, parallel-group noninferiority trial that included 1,200 infants aged 60 to 90 days to evaluate the immune efficacy and safety of Sabin-IPV compared with Salk-IPV (Sanofi Pasteur). The researchers randomly assigned the patients into experimental (Sabin-IPV) and control (Salk-IPV) groups, and each infant received three IV doses at 30-day intervals and a booster at age 18 months.
There were 600, 591 and 581 infants, respectively, who received the first, second and third doses of Sabin-IPV; while the controls who received Salk-IPV numbered 600, 584 and 573 for each consecutive dose. More than 90% of infants in the experimental group developed antibodies for poliovirus type I (100%), type II (94.9%) and type III (99%) at 1 month after their third dose. Similar results occurred in the control group.
Both groups underwent a significant decline in neutralizing antibodies against all polio types before receiving a booster shot. Subsequently, both Sabin-IPV and Salk-IPV infants experienced significant immune response against all three poliovirus types.
In addition, “645 and 688 episodes of unsolicited adverse events were reported among 323 and 326 infants in both the Sabin-IPV and Salk-IPV groups, and almost all were attributed to respiratory tract infections (43.3% in the Sabin-IPV group; 43.8% in the Salk-IPV group),” the researchers wrote.
“These findings, especially its immunogenicity as similar with that of Salk-IPV, suggest that Sabin-IPV is a viable alternative to OPV, especially for use in the [expanded program on immunization] in developing countries,” the researchers wrote. “The use of Sabin-IPV could potentially prevent the occurrence of VAPP in these areas and will be helpful for new children immunization programs of the single dose of IPV preceding the bivalent OPV, which is recommended by WHO and actually is processed for trivalent OPV replacement in the most developing areas recently.” – by Kate Sherrer
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Walter A. Orenstein
Julie Garon
The Global Polio Eradication and Endgame Strategic Plan calls for an expanded role of IPV in the coming years. The phased withdrawal of OPV is designed to ensure eradication not only of wild polioviruses but also of polio caused by vaccine viruses including vaccine-associated paralytic poliomyelitis (VAPP) cases and circulating vaccine-derived polioviruses (VDPVs), vaccine viruses which through passage from one susceptible to another mutate and regain both the neurovirulence and transmissibility properties of wild polioviruses leading to outbreaks of polio.
The introduction and use of IPV is to provide some level of population immunity to decrease the risk of outbreaks should live polioviruses be reintroduced, such as through a break in laboratory containment. Also, if live polioviruses are introduced, IPV may also facilitate termination of transmission by assuring both a level of polio immunity as well as a polio primed population who would respond better to vaccine used in response to the introduction. Thus, IPV will be needed through certification of eradication of wild polioviruses and at least 5 years afterwards.
Currently, all OPV-using countries are in the process of introducing at least 1 dose of IPV into routine immunization schedules and global manufacturers have experienced difficulty scaling up production to meet the historic levels of demand. As of September, 2016, more than 20 countries have not been able to introduce IPV because of supply shortages. “Traditional” Salk IPV production requires generation of high volumes of high titer wild poliovirus. A risk of intentional or unintentional release from production facilities is a concern in low- income countries where transmissibility of polioviruses is high. For this reason, IPV is currently manufactured in only a few European facilities. At this point in time, there is an urgent need to increase production capacity of IPV, globally.
In this study, Liao et al describe a phase 3 clinical trial of a Sabin-IPV vaccine that shows non-inferior immunogenicity and a similar safety profile to the Salk-IPV currently used today. Licensing and production of a Sabin strain-based IPV offers a way to expand IPV manufacturing to more countries worldwide since manufacture may potentially be undertaken in developing countries and ease current global IPV supply constraints. In addition, Sabin IPV may decrease cost of IPV, an important factor in assuring IPV is both introduced and continues to be used.
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