More than a month after health officials started a vaccine campaign in response to a deadly Ebola outbreak in the Congo, the World Health Organization reports that the spread of the disease has "largely been contained."

In a Friday update (PDF), WHO reported that there haven't been any new confirmed cases in the outbreak since June 6. There have been four recent suspected cases. Despite the progress, the agency says "there should be no room for laxity and complacency until the outbreak is controlled."

The news comes about a month after officials started vaccinations with Merck's late-stage Ebola vaccine. Through the program, 3,200 people in the area have received vaccines. The "ring vaccination" effort is targeting health professionals, people who have had exposure to the virus and their contacts. In a previous phase 3 ring vaccination trial, Merck's vaccine posted 100% efficacy.

The V920 vaccine was initially engineered by scientists from the Public Health Agency of Canada’s National Microbiology Laboratory and later licensed to a subsidiary of NewLink Genetics. In late 2014, during a major Ebola outbreak that claimed more than 10,000 lives, Merck licensed the candidate from NewLink Genetics to accelerate development.

During the current outbreak, officials have recorded 61 cases, with 38 confirmed by laboratory testing, according to WHO. The outbreak has claimed 28 lives.

RELATED: Merck's experimental Ebola shot gets set to fight deadly new outbreak in Congo An Ebola outbreak last year in the Democratic Republic of Congo spanned 42 days and claimed four lives, the agency said. Officials prepped the vaccine for potential use against that outbreak but never deployed the shot.

Of course, it was the large epidemic in West Africa in 2014 and 2015 that created anger and frustration among the scientific community that an Ebola vaccine wasn't available to help fight off the disease. Zika followed, further demonstrating that the vaccine development process wasn't adequately addressing potential threats.

Since then, governments, nonprofits and pharma companies have come together to form the Coalition for Epidemic Preparedness Innovations, an international group designed to prepare for potential epidemics before they happen. The group set the MERS-CoV, Lassa and Nipah viruses as its initial targets.