Vaccine Strain Poliovirus Detected in Gaza Sewage—WHO Sending a Million Doses of Polio Vaccine

In response to a statement last week by the Palestinian Ministry of Health declaring  that the Gaza Strip is “epidemic area“ for polio,  the World Health Organization (WHO) announced it will send more than one million doses of polio vaccine to be administered over the next few weeks even though the poliovirus detected in Palestine area sewage is vaccine-derived and no polio cases have been reported.^{1 2 3 4 5 6}

According to UN News, on July 16, 2024, the WHO determined that “vaccine-derived poliovirus type 2 (VDPV2) had been identified at six locations in sewage samples collected [in June] from Khan Younis and Deir Al-Balah,” suggesting that children in Gaza may now be at risk for vaccine strain polio. The warning comes as diarrhoeal diseases, respiratory infections, and hepatitis A have been circulating in the Palestinian area since the start of the war between Israel and Hamas last year.^{1 2 3 5}

While sanitary conditions continue to deteriorate in Gaza due to a lack of clean water and sewage spilling into the streets near camps where displaced people are living, dysentery and gastroenteritis are also spreading. Wild type and vaccine strain polio is mainly spread through the fecal-oral route when people come in contact with the body fluids of infected persons, which is facilitated in areas with poor sanitation.^{6 7 8}

WHO Director-General: “No Cases of Polio Have Been Recorded Yet”

“While no cases of polio have been recorded yet, without immediate action, it is just a matter of time before it reaches the thousands of children who have been left unprotected,” said WHO Director-General Tedros Adhanom Ghebreyesus. “I witnessed at first hand living conditions that are highly favorable for the spread of polio and other diseases,” said Hanan Balkhy, MD, WHO Regional Director for the Eastern Mediterranean.^{4 5}

Spread of infectious diseases is not uncommon in war-torn areas and Adhanom Ghebreyesus invoked the specter of wild-type polio spreading even though there have been global polio vaccination campaigns since the Salk inactivated polio vaccine (IPV) was licensed in 1955 and the Sabin live attenuated oral polio vaccine (OPV) was licensed in 1961. The live Sabin OPV, which replaced the inactivated Salk polio vaccine in global vaccination campaigns starting in the 1960s, can spread vaccine strain poliovirus and “passively” vaccinate those who come in close contact with the body fluids of a recently vaccinated person,. However OPV can also cause vaccine strain polio paralysis and most polio outbreaks and cases of polio-related paralysis today are caused by vaccine-derived strains.^{8 9}

As Adhanom Ghebreyesus noted (without referencing outbreaks of vaccine-derived polio):

Repeatedly, we have seen polio thrive in places hit by conflict and instability. In 2017, in war-torn Syria, an outbreak of variant poliovirus—a mutated form of the wild virus that can spread in under-immunised populations—left 74 children paralysed. In Somalia today, a decade-long civil war has resulted in the longest unbroken chain of variant poliovirus transmission globally, circulating since 2017. In Afghanistan and Pakistan, the last two countries where children are paralysed by wild polio, humanitarian crises and insecurity have prevented the world from stomping out the virus for good. Now, children trapped in Gaza face this same threat and are left with nowhere to turn.⁵

Regional Spread of Poliovirus a Possibility

With the detection of vaccine-derived poliovirus in Gaza, health authorities have expressed concern that polio could spread throughout the region, including Israel, but, again, do not make a distinction between wild type and vaccine-derived poliovirus.

“It will be almost impossible to stop the ecological movement of the virus,” said Lior Nesher, MD, director of the Infectious Disease Institute at Soroka Medical Hospital in Be’er Sheva, Israel. He added, “The disease does not respect borders.”⁷

Israel’s Ministry of Health has begun a campaign offering polio vaccination boosters to members of the Israel Defense Forces (IDF) stationed in Gaza. The boosters are not compulsory. Despite the vaccination campaign, there remains concern that vaccine-derived poliovirus may still be spread by IDF soldiers returning to Israel and other countries. Dr. Nesher noted that the dangers lies when soldiers return from Gaza and “carry the disease through mud, through their clothes, through their bowel movements.”^{7 10}

The WHO’s plan to distribute polio vaccines in Gaza will be coordinated with the IDF, although the logistics of this effort will be daunting, given the lack of a cease-fire agreement between combatants and the fact that only 16 of Gaza’s 36 hospitals are functional (with reduces services) and less than half of the primary health care facilities are operational. “The health care infrastructure is ruined. There is no capability enough to control this outbreak,” said Mithqal Abutaha, MD, program manager for Project HOPE, a global health non-governmental organization that runs clinics in Gaza.^{5 10}

VDPV2 Strain Linked to Oral Polio Vaccine

The VDPV2 strain that was found in sewer water in Gaza is linked to the oral poliovirus vaccine (OPV) that was last given in the United States in 2000 but has continued to be used in global polio vaccination campaigns in dozens of other countries, primarily in Africa, Asia, Latin America and the Middle East. Because the OPV contains a weakened but live form of the poliovirus, it can cause paralysis in the vaccinated person or a close contact. In 2022, state health authorities in New York confirmed a young adult in Rockland County had contracted VDPV2 which could have been transmitted by someone who received the OPV overseas.^{11 12 13 14}

In the mid-1990s, co-founders of the National Vaccine Information Center (NVIC) called on the Centers for Disease Control and Prevention (CDC) to discontinue use of live OPV in the U.S. and replace it with the IPV that cannot cause vaccine strain polio.^{14 15}

It is unclear what kind of polio vaccine will be provided by the WHO to the people living in Gaza.

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