In mid-August, a 10-month-old baby in Deir al Balah was confirmed to have polio. It marks the first case of polio in Gaza in 25 years.   The polio virus can cause irreversible paralysis within hours of infection. It is particularly dangerous for young children. It can also spread rapidly through poor sanitation and exposure to faeces, and contaminated water supplies – both of which are prevalent in Gaza.    Worldwide, the most effective way to prevent a polio outbreak is through vaccination. However, most children in Gaza have not been vaccinated, and at least 640,000 children under 10 years old in Gaza need vaccination.     While Israeli blockade has impeded most delivery of vaccinations, a successful immunisation campaign, by UNRWA and their partners began on 1 September, despite the numerous challenges posed by the Israel military, through vaccine detainment and sudden evacuation orders.   The first two of six stages of the campaign have been successfully completed so far (as of 9 September), giving a first vaccination dose to 446,163 children under 10 years old in Deir al Balah and Khan Younis. It is now planned to expand to northern Gaza. Each child will need a second round of repeat doses in late September or October for the vaccine to be effective.