With the recent reports of poliovirus detection in wastewater samples from the New York City metropolitan area, many people want to understand what is happening, why it is happening and what it means. However, in order to fully understand what is going on, it is necessary to understand some important aspects of the history of polio and polio vaccination.
Polio is a once-ubiquitous fecal-oral-borne virus. While the idea of polio may conjure up images of iron lungs and leg braces, most infections with the People with the virus never show any symptoms — it’s estimated that about 1 in 200 infections can lead to horrific, sometimes fatal, complications of paralysis.
The successful efforts of Jonas Salk, MD, in my hometown of Pittsburgh in the 1950s led to the development of a safe and effective polio vaccine. Salk and his vaccine – which received an offer from a ticker march (imagine a vaccine today!) – could help reduce the burden of paralytic polio in the United States. His injectable inactivated vaccine was soon replaced by an attenuated oral vaccine developed by Albert Sabin, MD.
Unraveling what is happening today in New York, Israel, London and elsewhere requires understanding the differences between these two life-saving vaccines. The Salk vaccine is a standard injectable inactivated virus vaccine, while the Sabin vaccine contains a replicating altered poliovirus and is usually given orally on a sugar cube. Not only is the Sabine vaccine cheaper and easier to administer because it doesn’t require syringes, needles, or a trained person to administer it — it’s also considered advantageous by its very nature. Polio is a fecal-oral pathogen, and the Sabin vaccine, as an oral vaccine, more naturally mimics the natural route of infection, thus eliciting a different and more potent immune response than the injectable Salk vaccine. In addition, because it is a “live” vaccine, the vaccine virus is shed, and close contacts of the vaccinated person can be passively immunized. For these reasons, the Sabin vaccine ended up being the more dominant and popular vaccine than the Salk vaccine.
However, as polio receded as a public health threat, the Sabin vaccine caused rare complications. The vaccine became intolerable in many Western countries. In rare cases, the “live” nature of Sabin vaccine may lead to vaccine-related paralytic polio. In rarer cases, the virus may mutate or recombine with other viruses to become a circulating vaccine-derived poliovirus (cVDPV) that can infect other viruses and, in some cases, cause paralysis. That’s why 20 years ago – when polio was no longer a problem at home – the US switched to a full Salk polio vaccine program for children instead of Sabine Oral Polio Vaccine (OPV) and injectable polio combination vaccine. But many countries, especially those still endemic for wild polio, still use OPV.
Currently, wild polio is only known to be endemic in Afghanistan, Pakistan, and Mozambique, and should be considered in my analysis to be associated with cVDPV in New York and elsewhere Questions are different. Although many news reports conflate wild polio and vaccine-derived polio, they are different problems.
Therefore, as long as OPV is used, there is a risk of disease from cVDPV. are unvaccinated individuals.
The fact that the strains found in the New York area bear little resemblance to the vaccine-derived strains circulating in Israel shows the global nature of the problem. It must be emphasized that cVDPV becomes a significant problem only when non-immune individuals are available for infection. cVDPV does not pose a significant risk if vaccination rates in Israel, London, or New York City are high enough. Therefore, the risk of cVDPVs is artificial when people are not adequately vaccinated. Based on estimated circulation levels, unvaccinated people are likely to experience more cases of paralysis, although a high number of paralysis cases is unlikely based on high vaccination rates.
In response, healthcare professionals and policymakers need to encourage widespread immunization in areas where cVDPV is found. Not surprisingly, this problem was found in the same location where a recent large measles outbreak occurred. I suspect that there may be cVDPV transmission in other regions as well, and wider wastewater surveillance as well as targeted catch-up immunization is critical. I cannot stress this enough: high vaccination rates are needed to recover. I worry that the progress of the anti-vaccine movement has had real consequences.
Amesh Adalja, MD, is a senior scholar at the Johns Hopkins Center for Health Security and a practicing infectious disease, critical care and emergency department in Pittsburgh physician.
Adalja is a shareholder of Merck & Co., which is the owner of certain polio vaccines manufacturer.