The United Nations announcement on Sunday that it would demand a record-shattering $6.5bn to fund humanitarian efforts in Syria – as much as it will spend in response everywhere else in the world, combined – underscored the scale of the humanitarian tragedy in Syria.

The same day, the International Rescue Committee released a statement detailing the humanitarian challenge inside Syria: the cost of bread has risen 500%, nearly four-in-five communities are struggling to access food, one in two communities is concerned about clean water, and a shortage of medical supplies is pervasive.

In March 2014, when the Syrian civil war hits the three year anniversary mark, the UN will be supporting roughly three out of four of Syria's 20 million citizens: including 2.5 million Syrians in what the UN designates as "hard-to-reach" areas – areas within Syria largely under rebel control – and 2.3 million who have fled the nation entirely.

But no effort will receive more scrutiny than the UN's push to prevent a polio epidemic. The UN has repeatedly exhorted Syria to allow humanitarian access across conflict lines for immunization campaigns, but is still legally obligated to coordinate with the government.

As the United States and its western partners fret over a perceived lack-of-options in Syria – scared of arming increasingly extremist Islamist rebel groups or legitimizing President Bashar al-Assad four months after chemical weapons attacks killed 1,400 – it is crucial that these nations bring all pressure available on the Syrian government to allow the UN humanitarian access across conflict zones.

By ensuring that Assad's government allows the UN to distribute polio vaccinations in rebel-held or contested areas, the international community can prevent another senseless humanitarian tragedy.

A Reuters report last week alleged that the eastern, contested province of Deir e-Zor, where the disease was first detected, had been purposefully excluded by the Syrian government in a 2012 campaign, citing the region's depopulation. Less than a year later, in October of this year, the World Health Organization documented the first 15 cases of the heavily contagious disease in Syria since 1999 in Deir e-Zor, and the outbreak has since spread to largely rebel-controlled Aleppo and the Damascus suburbs.

Once it appears, the incurable disease, which can paralyze children under five in a matter of hours, is very challenging to contain: only 1-in-200 children carrying polio actually show symptoms. Immunization rates of Syrian children have plummeted to 70%, from pre-war levels near 90%.

"By the time we find a single case, the horse is out of the barn, so to speak," said Oliver Rosenbauer, a spokesperson with the World Health Organization's Global Polio Eradication Unit in Geneva.

Peter Kessler, a spokesperson for the United Nations High Commissioner for Refugees in Amman, Jordan said:

For a polio campaign to be effective, roughly 90% or more of the population needs to be vaccinated to stamp the disease out.

Immediately after the outbreak, Unicef and the WHO launched a campaign to vaccinate 23 million children across the Middle East, scrambling to reach 1.6 million children inside Syria.

But the campaign's success will depend on its ability to vaccinate children in rebel-held areas, where the Syrian government has long-prevented the entry of food and medicine and where healthcare systems have continued to crumble.

In November, the United Nations airlifted 538,000 polio vaccinations from its headquarters in Damascus to a field-office in the northeastern city of al-Hasakeh. Those vaccinations, later distributed overland throughout eastern Syria, nevertheless bypassed villages blockaded by government forces just a dozen miles from the UN headquarters in Damascus, where polio has already been detected.

"We in East Ghouta are not included in vaccination campaigns," said Majed Abu Ali, who works at the United Medical Office in the East Ghouta suburbs of Damascus, subjected to more than a year of a crippling government blockade. As the battle for Ghouta continues, the Syrian government has not allowed the distribution of food or medicines, only the evacuation of starving citizens.

I live in Jordan, home to more than 570,000 Syrian refugees. Here, the UN will use some of its $6.5bn request to immunize every Syrian child who arrives, and all who have already crossed the border.

Every day, I learn of the myriad ways in which war can senselessly destroy lives. Certainly among the most senseless is a child being paralyzed by a disease for which an immunization was found in 1955. In 2014, let us hope that the United States and its allies can use their influence to ensure that the Syrian government allows humanitarian agencies to distribute polio vaccines throughout Syria, even in rebel-controlled areas.