Beirut - Since the beginning of the Syrian crisis in early 2011, war has all but destroyed the country's healthcare system. Hundreds of doctors and health practitioners have been killed or have fled to neighbouring countries, drug supply routes have been destroyed, and government forces have routinely and indiscriminately targeted hospitals.

As a result - and on top of unsanitary living conditions and a sharp drop in overall vaccination coverage - there have been outbreaks of communicable diseases such as hepatitis, leishmaniasis, polio, and tuberculosis.

Polio, eliminated in Syria in 1995, re-emerged last year and spread across large swaths of the country's opposition-held north.The highly contagious disease also re-emerged in Iraq this year for the first time since 2000, infecting a baby boy and a young girl. The World Health Organisation (WHO) and UNICEF responded by launching a mass polio vaccination campaign across the region, but health workers say the response was too slow.

"The first cases of flaccid paralysis were diagnosed clinically in July of 2013, and they weren't confirmed by WHO until October," Zaher Sahloul, president of the Syrian American Medical Society (SAMS), told Al Jazeera. "The WHO initially underestimated the risk and took the Syrian line."

Despite the odds, a hugely successful polio campaign has been ongoing in Syria - largely thanks to the Polio Task Force, a coalition of Syrian groups including SAMS, the opposition-linked Assistance and Coordination Unit (ACU) and about half a dozen other groups supported by the Turkish Ministry of Health. Some 8,200 volunteers, including a network of activists and doctors, have completed seven rounds of vaccinations, inoculating about 1.4 million of the estimated 1.5 million children in the area it covers.

OPINION: Polio in Syria: putting children above politics

But those delivering the vaccinations have faced insurmountable challenges amid the country's plummeting security situation, including the deaths of more than four volunteers.

"[The volunteers] have faced shelling, explosive barrel bombs and were subjected to sniper fire while working," Bashir Taj al-Din, a technical coordinator with the ACU, told Al Jazeera.



Doctors running the campaign said they also had to work against rumours that vaccination could cause side effects such as AIDS and impotence, thwarting their efforts to vaccinate as many children as possible against diseases like polio, measles and rubella.

In spite of the grim picture in Syria, we should call for optimism. - Zaher Sahloul, president of the Syrian American Medical Society

Salah Haithami, the regional Middle East outbreak coordinator at WHO, told Al Jazeera that in its October assessment of Syria's polio vaccination campaign, parents' reluctance to have their children vaccinated had increased. "We found out that some people had spread rumours on social media that the vaccine is toxic," Haithami said, attributing the rumours to an unnamed "enemy country".

Healthcare workers have tried to mitigate the problem by vaccinating children in front of their parents to assure them it was safe, Haithami said.

"I think part of the issue was that the rumours were related to the measles vaccine incident. It definitely played a role in making some families afraid," he added, referring to an incident in September in which 15 children died 10 minutes after receiving a measles vaccination in Syria's northeastern Idlib province. The UN-sponsored vaccine, administered to 75 children, had been accidentally mixed with atracurium, a muscle relaxant commonly used in surgery. The packaging for atracurium is similar to that of the regular diluent used with the vaccine, and both had been kept in the same refrigerator, explained Khaled Almilaji, the health department manager at the ACU.

Some health experts believe that the error, which resulted in a suspension of the measles vaccination campaign in Idlib and Deir ez-Zor provinces, will have serious ramifications for future vaccination efforts. The incident gravely affected the level of trust between aid providers and civilians, said policy consultant and public health expert Adam Coutts.

"The case reflects how bad the situation is on the ground, with a lack of staff with adequate medical training and knowledge," Coutts told Al Jazeera. "It will make it even more difficult to convince parents to bring their children to centres to be immunised for all diseases, which provides the conditions for diseases to increase and spread."

Haithami urged those who were part of the measles vaccination campaign in Syria to resume inoculating children as soon as possible: "It's a tragedy to lose 15 children but if we stop vaccines, we may lose hundreds. It is the high season for the transmission of measles."

RELATED: UN: vaccine mistake killed Syrian children

Meanwhile, Annie Sparrow, deputy director of the Human Rights Programme at the Icahn School of Medicine in New York, recently brought the issue of polio back into the spotlight in a piece for the New York Review of Books. She alleged that the UK-based NGO Save the Children let 250,000 doses of polio vaccine expire at a time of critical need, when the vaccination campaign in Syria was already facing delays due to a lack of vaccines. Save the Children denied the allegations and said no child had missed out on the vaccine.

"Due to the circumstances of the conflict in Syria, there have of course been local issues with supply, but this has not stopped a massive series of successful campaigns," WHO spokeswoman Sona Bari told Al Jazeera. "It is still too early to say definitely that the outbreak has been stopped, [but] a major epidemic has clearly been averted."

Regardless, thousands of children in remote areas continue to miss out on being vaccinated. According to Humanitarian Tracker, an organisation monitoring the polio situation in Syria, more than 22,000 children missed out on being inoculated during the second phase of the campaign. In the sixth round, more than 1,100 children in Deir ez-Zour missed out, while almost 800 missed out in al-Raqqa. Still, as Haithami pointed out, there has only been one case of polio this year.

"[Polio is now] of limited threat, only in some areas that vaccination did not occur and where malnutrition of children and impaired access due to fighting and siege situations may impede regular vaccination [efforts]," Sahloul said. "In spite of the grim picture in Syria, we should call for optimism."