The same strain of poliovirus that paralyzed an unvaccinated young man in New York’s Rockland County this summer is still spreading to several areas of the state in early October, according to a sewage monitoring study released Friday by the Centers for Disease Control and Prevention.
The finding suggests 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 zip code has a polio vaccination rate for children under age 2 of just 37 percent, according to state data. In Orange, a postal code has a vaccination rate of only 31%. Rockland and Orange county-wide vaccination rates are about 60% and about 59%, respectively.
Sullivan County has not provided the state with vaccination rate data at the zip code level. But in an August news release, County Public Health Director Nancy McGraw suggested some areas of the county have low rates similar to Rockland and Orange.
“Sullivan County has an overall polio vaccination rate of 62.33%, but some areas of the county have lower vaccination rates, and because polio can spread very easily, it’s important that everyone be vaccinated,” McGraw said at the time. “Public health has a safe, proven vaccine available for children two months or older. We work with the state to get adult providers vaccinated. If adults need a vaccine, then we encourage them [sic] to contact their healthcare provider.
Most adults and children in the United States are vaccinated against poliomyelitis. 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 4 and 6 years of age. Only the first three doses are 99 percent to 100 However, the percent effectiveness in preventing paralytic disease and immunization coverage rates indicate the percentage of 2-year-olds who have followed the recommended immunization schedule for the first three injections.
But, in low-immunization pockets, like those in several New York counties, poliovirus — in this case, a revertant virus derived from an oral vaccine used overseas that passed between unvaccinated people — may 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 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 (about 8%) samples taken from 10 sewers tested positive for the 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 was from a different poliovirus that was unrelated to Rockland’s case, suggesting that more than one strain of poliovirus was introduced into the United States.
The strain of poliovirus in the Rockland case has been genetically linked to viruses spreading in London and Israel.
The fact that samples as recent as October 4, 5 and 6 tested positive for poliovirus which has already paralyzed one person, suggests 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.