UNITED NATIONS, Aug. 6 (Xinhua) -- The United Nations and the Yemeni Ministry of Health have launched a week-long cholera vaccination campaign, targeting the most vulnerable 500,000 people in and around the battle-scarred city of Hudaydah.

The United Nations Children's Fund (UNICEF) said Monday that over a year after cholera broke out in Yemen, killing more than 2,000 people, the disease is back and spreading fast in the Houthi-held port city of Hudaydah -- a target of continued air strikes by the Saudi-led coalition to regain control of the city.

Other mitigating measures implemented by humanitarian organizations include the continued provision of safe drinking water and sanitation facilities, according to the UNICEF.

Yemen's conflict has its roots in uprisings that date back to 2011, but fighting escalated in March 2015, when an international coalition led by Saudi Arabia intervened militarily at the request of Yemen's president.

More than 70 percent of all humanitarian aid and food imports get access to the country through the docks of Hudaydah, which was one of the worst-hit cities in Yemen's cholera outbreak last year.

On Thursday, the main hospital in Hudaydah was hit during an airstrike, further compounding the dire health situation in the city.

Fighting is still raging across much of Yemen and the escalating humanitarian crisis is the most acute of anywhere in the world this year, the UNICEF said.

As of Monday, about 88,000 people had received the cholera vaccine. This is the second of the three phases of the campaign led by the World Health Organization and the UNICEF with the first one administered in Aden.