Why Aid Agencies Are Rushing Polio Vaccines to Gaza

In July, health officials made a disturbing discovery in Gaza: the polio virus, a global scourge, had been found in sewage samples. This month, the news got even worse. A 10-month-old baby has contracted polio and is now paralyzed in one leg.

It is the first confirmed case of polio in Gaza in 25 years. Now, international agencies are sending more than 1.6 million doses of oral polio vaccine to the conflict zone as part of an ambitious effort to vaccinate 640,000 children under the age of 10.

Israel agreed to three halts in hostilities starting Sunday to facilitate the campaign.

Health officials have warned for months that the conflict in Gaza could eventually lead to a major resurgence of infectious diseases. Some experts fear that transmission of the polio virus — which attacks the nervous system and can paralyze the spine and respiratory system, and in some cases, death — may already be widespread.

Here’s what you need to know.

How is it possible that a polio epidemic occurred in the Gaza Strip?

Of the three naturally occurring “wild-type” viruses, only type 1 survived; types 2 and 3 have been eliminated.

But there is another form to worry about: the so-called vaccine-derived poliovirus. This form is responsible for most epidemics around the world right now.

Since 2000, the United States and most wealthy countries have used an injectable vaccine that does not contain the live virus. But many low-income countries still rely on oral vaccines that contain live, weakened polio virus designed to trigger an immune response without causing earnest disease.

But a child receiving the oral vaccine may shed weakened virus in stool or body secretions. This virus may not be as harmful as wild-type polio—at first.

If vaccination rates in a given population are insufficient, the vaccine-derived polio virus can spread widely and unhindered, undergoing genetic changes and eventually evolving into a type capable of causing paralysis and epidemics.

How did the conflict contribute to this?

Polio vaccination rates in Gaza were around 99 percent in 2022, but have fallen dramatically. The child who was infected was not vaccinated.

At the same time, most of Gaza’s 2.2 million residents have fled their homes, seeking makeshift shelters where a lack of immaculate water and sanitation, as well as overcrowding, make the area susceptible to the spread of disease.

In many communities, untreated sewage flows freely near momentary housing. Diseases transmitted through contaminated food or water or close person-to-person contact pose a earnest threat.

Airstrikes and ground fighting have decimated many of the territory’s hospitals and clinics, and fewer than half of its facilities remain even partially functional. As a result, existing health infrastructure is largely dedicated to those suffering from war injuries, rather than public hygiene and disease prevention.

In the midst of the crisis, disease is on the rise. There have been at least 500,000 cases of diarrhea and almost a million acute respiratory infections. The WHO has reported 100,000 cases of lice and scabies, and about the same number of cases of acute hepatitis syndrome or suspected hepatitis A.

What is the plan for Gaza?

To stem a potential outbreak, global health officials have launched an urgent campaign to get vaccines to hundreds of thousands of Palestinian children, expected to begin Sunday.

According to the WHO, the oral vaccines being transported to Gaza will be against poliovirus type 2. The campaign will involve 708 teams and 2,700 health workers.

According to UNICEF, due to destitute sanitation conditions in Gaza, at least 95 percent of children will need to receive two doses of the vaccine to reduce the risk of polio re-emerging in the region.

The Israeli Defense Ministry announced that the vaccination campaign will take place during three humanitarian breaks.

What does this mean for global efforts to eradicate polio?

Compact answer: Nobody knows.

The polio virus found in Gaza did not emerge there—it was somehow introduced, perhaps from Egypt. Spread beyond Gaza remains possible as long as the virus circulates; it is impossible to say whether cases can be contained in Gaza.

More than 30 years ago, the World Health Assembly passed a resolution to eradicate polio, which led to mass vaccination campaigns that have reduced the disease by more than 99 percent worldwide. Wild polio is now known to occur in only two strongholds—Pakistan and Afghanistan.

But Oliver Rosenbauer, spokesman for the Global Polio Eradication Initiative, said true elimination of the disease would require a “double strike”: eliminating wild polio from these sites and phasing out the live virus component of oral vaccines.

For now, the best protection against polio in any community is still “herd immunity” through vaccination. In places where almost all children are vaccinated, the likelihood of the disease spreading is minimal. But the unvaccinated child remains at risk, as the 2022 outbreak shows. who reached New York.

“As long as polio exists anywhere,” Mr. Rosenbauer said, “all countries will be at risk.”