A groundbreaking study has shaken long-held beliefs about how the poliovirus is transmitted, providing new insights into its spread. Researchers, including T. Jacob John (now retired) from Christian Medical College, Vellore, Dhanya Dharmapalan, Robert Steinglass and Norbert Hirschhorn from Apollo Hospitals, Navi Mumbai, revisited wild and vaccine-derived poliovirus mode of communication. Their findings, published in Infectious Diseases, show that poliovirus is primarily transmitted through the respiratory tract, contradicting the widely accepted belief that poliovirus is spread through food and water contaminated with feces .
According to Dr. Jacob John, the global polio eradication campaign focuses on the fecal-oral transmission of the virus, which occurs in food and water contaminated by sewage. . However, he believes the evidence clearly shows respiratory transmission is the main way the virus spreads from person to person. He added that this focus on contaminated food and water may be because polio was endemic only in low-income countries with poor sanitation, ignoring other key factors such as high birth rates, crowded living conditions and transportation methods. Adults and older children interact socially with infants.
Throughout the study, the team carefully examined historical data and conducted a thorough analysis of how the virus was spreading in the community. Their findings suggest that focusing on the wrong transmission routes has delayed efforts to eradicate polio. “Based on current research and observations, we have found no evidence of transmission through contaminated food or water, but all available information supports a respiratory route,” Dr. John explained. He also pointed out that this misunderstanding has led to the belief that live oral polio vaccine (OPV) is essential to interrupt the transmission of wild poliovirus and vaccine-derived poliovirus. This explains why eradication programs have failed to completely halt transmission in many countries. In these countries, the vaccine efficacy of oral polio vaccine is unacceptably low. In comparison, inactivated polio vaccine has proven to be more effective, especially since the virus is mainly transmitted through the respiratory tract. In these countries, the vaccine efficacy of inactivated poliovirus vaccine (IPV) is excellent, as in other countries where IPV has been used to eliminate poliovirus.
Dr. John also took a closer look at past studies linking polio to poor sanitation and water quality. While injecting children with OPV can boost their immunity through oral route of infection, he pointed out that this does not reflect how the virus is naturally transmitted. Children who receive OPV rarely pass the virus to others, raising questions about whether the virus actually enters the body through contaminated food or water. “So far, Sabin’s challenge of proving or disproving respiratory transmission remains unresolved,” said Dr. Johns, referring to the scientists who developed OPV, who called for more research into whether poliovirus is transmitted through inhalation of oral droplets. .
The study strongly supports a respiratory route of transmission, which is more consistent with existing data. Dr. John emphasized that continued reliance on OPV has led to outbreaks of mutant vaccine strains, which may lead to sporadic outbreaks of polio. These outbreaks are particularly common in areas where OPV is used, creating further obstacles to disease elimination. Vaccine-derived virulent mutant viruses are regularly exported to polio-free countries, making the situation worse.
One of the study’s most important findings is the role of reinfection in immune individuals, which plays a crucial role in the continued spread of the virus. People who become reinfected won’t show any symptoms, but they can still spread the virus to others, especially in places where older people and infants are in close contact with each other. Dr. John believes that this silent transmission between those who have been infected and those who are later infected again is the main reason why the virus continues to spread, especially in areas where vaccine coverage is uneven or the vaccine efficacy is too low.
By establishing that droplet/aerosol transmission is the primary mode of poliovirus transmission, Dr. John proposes a clear path forward: a global shift from OPV to IPV. Unlike oral vaccines, IPV is neither contagious nor spreadable from person to person, making it completely safe. “Only inactivated vaccines can be used in a polio-free world,” noted Dr. John, who urged health authorities around the world to speed up the transition from oral to inactivated vaccines to eradicate polio.
Dr John summarized the findings, saying: “Virulent poliovirus, whether wild or vaccine-derived, is transmitted through the respiratory tract, similar to other infectious childhood diseases such as measles, rubella and diphtheria.” This cognitive shift not only has major implications for vaccination strategies, but also poses a challenge to public health policies that have long focused on improving sanitation and water security as a way to stop polio.
As the world continues to battle the poliovirus, these findings could be critical in developing next steps to completely eradicate the disease. If global health organizations follow Dr. John’s advice, focus on respiratory transmission and switch to inactivated vaccines, the long-awaited goal of a polio-free world may finally be achieved.
Journal reference
John, T. J., Dharmapalan, D., Steinglass, R., & Hirschhorn, N. (2024). “Respiratory transmission routes of virulent poliovirus.” Infectious Diseases. DOI: https://doi.org/10.1080/23744235.2024.2392791
About the author
T James John (MBBS, DCH, FRCP (Edin), PhD, DSc) trained in Pediatrics in India and UK and in Pediatric Infectious Diseases in USA. He spent almost his entire career at the Christian Medical College in Vellore, India, where he established India’s first diagnostic virology laboratory in 1967. Ministry, Government) named as National Center of Excellence India).
He began promoting childhood immunization in India in 1967 (seven years before the launch of the World Health Organization’s EPI) and is generally known as the “Father of Immunization” in India. He was elected President of the Indian Association of Medical Microbiologists (1984) and President of the Indian Society of Pediatrics (1999). From 1984 to 1992, he served on Rotary International’s PolioPlus Committee and the Health-Hunger-Humanity Committee. In 1992, he was awarded the title of “Medical Personality of the Year 1990” by the Medical Council of India.
Daniya Damapalan (MD, FIAP, FPIDS) is Senior Consultant, Pediatric Infectious Diseases, Apollo Hospitals, Navi Mumbai. She is the editor of nineteen pediatric textbooks and co-authored with TJ John the book Polio: Eradicating the Chaos. Diseases and Their Treatments” (2021)
Robert Stanglass (MPH, Johns Hopkins School of Hygiene and Public Health) For nearly 50 years, he has worked primarily for the World Health Organization and John Snow Corporation, strengthening immunization programs, vaccine-preventable disease control, and new vaccines in nearly 50 resource-poor countries. of launch.
Norbert Hirshhorn (Co-founder (M.D.) of John Snow, Inc. in the United States helped develop oral rehydration solutions for the treatment of diarrhea, from clinical to national programs. He has been honored by the Dana and Pauline Foundation and Columbia University, and was hailed as an “America’s Health Hero” by President Clinton.
