India's Drug Regulator Blocks 6-in-1 Vaccine Trial Over Chinese Polio Strain Safety Concerns
In a significant move prioritizing public health security, India's Central Drugs Standard Control Organisation (CDSCO) has rejected a proposal by Indian Immunologicals Ltd (IIL) to conduct human trials for a 'six-in-one' pediatric vaccine. The decision, confirmed by government officials and documents, stems from serious concerns about the use of Chinese-sourced poliovirus antigens that could potentially undermine India's hard-earned polio-free status.
Zero Tolerance for Polio-Related Risks
The regulatory rejection highlights India's uncompromising stance on polio containment. The subject expert committee (SEC) for vaccines conducted a high-level review that raised alarms about the safety and containment protocols associated with the Chinese polio strain. India has maintained its polio-free certification since 2014, and health authorities are determined to prevent any reintroduction of the virus through vaccine manufacturing processes.
According to regulatory documents, the primary objection centers on IIL's use of antigens from Chinese firm Sinovac. These specific Sabin Inactivated Poliovirus Vaccine (sIPV) antigens have never been incorporated into any approved polio vaccines—whether oral or injectable—within the Indian market. While approximately 10.01 million doses have been distributed globally, their usage has been restricted to China, Thailand, and Pakistan.
Critical Safety Gaps Identified
The expert committee identified several critical deficiencies in IIL's application during their December 22 meeting. The company failed to submit comprehensive post-marketing surveillance data, including real-world safety reports from the 10 million doses already distributed in other countries. Furthermore, no population studies exist for this specific hexavalent vaccine containing the Chinese-sourced antigens.
Health experts emphasize that even weakened polio strains in vaccines can potentially revert to more dangerous, virulent forms, leading to outbreaks of circulating vaccine-derived polioviruses (cVDPV). This risk is particularly concerning because Sabin strains used in such vaccines are inherently unstable. The committee concluded that a "considered decision cannot be taken at this stage" for the trials to proceed.
Containment Certification Requirements
A major sticking point involves poliovirus containment certification. The Chinese manufacturer of these antigens lacks approval under the World Health Organization's Poliovirus Containment Certification Scheme (CCS). This certification, implemented according to WHO's global action plan (GAP-III), provides essential assurance through stringent biosafety, biosecurity, and oversight mechanisms.
Dr. Naveen Thacker, executive director of the International Paediatric Association, emphasized the risks: "If there is an accidental leak from the lab during trials and it reverts back, then there will be issues in keeping polio-free status of India. Conducting such trials is simply not possible without robust, WHO-certified facilities."
What Hexavalent Vaccines Promise
The proposed vaccine represents a complex biological formulation designed to protect infants against six major diseases through a single injection: diphtheria, tetanus, whole-cell pertussis (whooping cough), hepatitis B, haemophilus influenzae type-B (Hib), and polio. By combining these protections, healthcare providers can reduce the number of injections children must endure, potentially easing parental burdens, lowering programmatic costs, and improving overall vaccine coverage.
Currently, India's Universal Immunization Programme (UIP)—one of the world's largest public health initiatives—does not incorporate any '6-in-1' vaccines nationally. The government program relies on a combination of pentavalent vaccine (protecting against five diseases) along with separate doses of oral polio vaccine (OPV) and fractional inactivated polio vaccine (fIPV).
Industry Response and Perspectives
Dr. K. Anand Kumar, managing director of IIL, defended the company's approach in response to queries. "It is important to understand that Sinovac is not a new or 'foreign' entity to our market," he stated, noting that the company has been supplying hepatitis-A vaccine bulk to an Indian company for nearly seven years.
Dr. Kumar emphasized that their partnership for Sabin inactivated polio vaccine bulk was based on "its superior safety profile," explaining that unlike Salk IPV derived from wild virus, the Sabin version uses an attenuated form that is then inactivated. He also clarified that these strains are distributed through WHO and the Netherlands Institute, with Sinovac's Sabin IPV already being WHO pre-qualified.
Other industry players have acknowledged the regulatory decision's significance. A spokesperson for Panacea Biotec, creator of the world's first fully liquid wP-based hexavalent vaccine EasySix, stated: "The SEC outcome signals India's regulator is aligning with WHO's Global Action Plan, making poliovirus facility certification non-negotiable."
Broader Implications for Vaccine Ecosystem
The regulatory decision comes at a time when multiple companies are vying to introduce hexavalent vaccines in India. Serum Institute of India, Panacea Biotec, GSK, and Sanofi already offer such vaccines in the private sector, while Biological E is also developing its version. The rejection underscores how biosafety considerations are taking precedence even as vaccine manufacturers push to introduce next-generation combination shots in a market that immunizes tens of millions of children annually.
Dr. Sanjeev Bagai, a senior consultant pediatrics and chairman of Nephron Clinics in New Delhi, cautioned: "Any additional strain of polio in the six-in-one vaccines must be compliant with all guidelines and regulations. If the Chinese data is missing, then it's best not to use that vaccine." He stressed that India's infectious disease surveillance should not be compromised, warning against bringing "a neurotropic unverifiable strain on Indian shores."
This regulatory action reinforces India's commitment to maintaining its polio-free status while navigating the complex landscape of next-generation vaccine development. As the global vaccine industry evolves, balancing innovation with stringent safety protocols remains paramount for protecting public health achievements.
