The same strain of poliovirus that paralyzed an unvaccinated young man in Rockland County in New York this summer is still spreading to several areas of the state in early October, according to a wastewater monitoring study released Friday by the Centers for Disease Control and Prevention.
The finding suggests that the virus continues to pose a serious threat to anyone in the unvaccinated or under-vaccinated region. The three counties with sustained transmission – Rockland, Orange, and Sullivan – have pockets of alarming vaccination rates.
In Rockland, for example, a county postcode has a polio vaccination rate for children under the age of 2 of just 37 percent, according to state data. In Orange, a postcode has a vaccination rate of only 31%. Vaccination rates across Rockland and Orange County are approximately 60% and 59%, respectively.
Sullivan County has not provided the state with data on the postcode vaccination rate. But in an August press release, County Public Health Director Nancy McGraw suggested that some areas of the county have similar low rates to Rockland and Orange.
“Sullivan County has an overall polio vaccination rate of 62.33 percent, but some areas in the county have lower vaccination rates and because polio can spread very easily, it’s important that everyone is vaccinated,” he said. McGraw at the time. “Public health has a safe and proven vaccine available for babies two months or older. We work with the state to get adult providers vaccinated. If adults need a vaccine, we encourage them [sic] to contact your doctor.
Most adults and children in the United States are vaccinated against polio. Since 2000, the country has relied on the inactivated polio vaccine (IPV), which is given in three doses before the age of 24 months, with a fourth injection between the ages of 4 and 6. Only the first three doses range from 99% to 100. However, the percentage efficacy in preventing paralytic disease and immune coverage rates indicate the percentage of 2-year-olds who followed the recommended immunization schedule for the first three injections.
Risk assessment
But, in low-vaccination bags, such as those in several New York counties, poliovirus – in this case, a reversible virus derived from an oral vaccine used overseas that has passed between unvaccinated people – could continue to spread. In the new CDC study released today, health officials sifted through wastewater monitoring data to see where and how significant this spread is.
They searched for the poliovirus among 1,076 samples taken from 48 sewers serving Rockland and 12 surrounding counties between March 9, 2022 and October 11, 2022. A total of 89 (approximately 8%) samples taken from 10 sewers tested positive for polio virus. Of the 89 samples, 82 were from counties outside of New York, taken from sewers in Nassau, Orange, Rockland and Sullivan counties. Of those 82 positive samples, 81 were genetically linked to the Rockland County patient and one, who was from Orange County, did not have sufficient genetic data to determine the link.
The other seven of the 89 positive samples were from New York City, one of which was linked to the Rockland case and five were of insufficient quality to determine the link. Interestingly, one came from a different poliovirus that was unrelated to the Rockland case, suggesting that more than one poliovirus strain had been introduced to the United States.
The poliovirus strain in the Rockland case has been genetically linked to the spread of the virus in London and Israel.
The fact that recent samples from October 4, 5 and 6 tested positive for the poliovirus that has already paralyzed one person suggests that others are still at risk in the United States.
“[A]Any unvaccinated or under-vaccinated adult or child living or working in Kings, Orange, Queens, Rockland or Sullivan counties, New York should complete the IPV series now, ”the study authors concluded.
