Twenty-two people have died of suspected diphtheria in conflict-ravaged Yemen, the World Health Organization said Friday, warning that a port and airport blockade had created a dire shortage of vaccines. The WHO said it had so far registered 197 suspected cases of diphtheria, a highly contagious and sometimes deadly infection that mostly affects the nose and throat, across Yemen. The UN health agency warned that a crippling aid blockade imposed on Yemen by a Saudi-led coalition last month had dramatically impacted its ability to re-stock supplies of the vaccine needed to halt the outbreak. "There is still not even one dose of Tetanus-Diphtheria vaccine in the country for children above five years and young adults," WHO spokesman Christian Lindmeier told reporters in Geneva. He said around 8.5 million doses of the vaccine were needed to provide those at risk with the required three immunisation jabs. The Saudi-led coalition battling Iran-backed Huthi rebels has now partially lifted the blockade it imposed on Yemen last month in response to a missile fired by the Huthis that was intercepted near Riyadh airport. A UN plane carrying desperately needed aid did manage to land in Sanaa last Saturday, bringing in 1.9 million doses of a vaccines for diphtheria, tetanus and other preventable diseases aimed at children under five, the UN children's agency said. One thousand doses of the antitoxins used to treat patients already infected with diphtheria meanwhile reached Sanaa on Monday, Lindmeier said, adding that a ship carrying 33 tonnes of medical supplies and other aid was expected to dock in Hodeida on Friday. But he warned that the situation was still dire, pointing out that due to "the long delay and closure of access there is a big backlog of material coming in." "We have a bottleneck with a lot of material and supplies waiting either in Djibouti or somewhere out there and waiting to be cleared." The diphtheria outbreak comes on top of a slew of other problems that together have created the world's biggest humanitarian crisis in Yemen. The United Nations has warned that unless the blockade is lifted, Yemen will face "the largest famine the world has seen for decades". Lindmeier also warned that fuel shortages and soaring prices caused by the blockade could risk disrupting fuel deliveries to 122 hospitals and could potentially force some to close. Nearly one million people have meanwhile been infected by cholera in the country this year, including more than 2,200 people who have died, fresh numbers from WHO showed. That adds to the some 8,600 people who have died in the conflict between the Saudi-backed government and rebels since 2015.