Washington, Jan 30 : American healthcare giant Johnson & Johnson's Covid-19 vaccine candidate is 66 per cent effective overall in preventing moderate to severe Covid-19, 28 days after inoculation, the company announced. The result was based on the Phase 3 ENSEMBLE study involving nearly 44,000 participants, Xinhua news agency quoted the company as saying on Friday. The study, designed to evaluate the efficacy and safety of the vaccine candidate in protecting moderate to severe Covid-19, was conducted in the US, Latin America and South Africa. The level of protection against moderate to severe Covid-19 infection was 72 per cent in the US, 66 per cent in Latin America and 57 per cent in South Africa, 28 days post-vaccination, according to the company. The company said it plans to apply to the US Food and Drug Administration (FDA) for emergency use authorization (EUA) to distribute the vaccine. The vaccine candidate was 85 per cent effective in preventing severe disease across all regions studied, 28 days after vaccination in all adults 18 years and older, according to the company. Efficacy against severe disease increased over time with no cases in vaccinated participants reported after day 49. "These topline results with a single-shot Covid-19 vaccine candidate represent a promising moment. The potential to significantly reduce the burden of severe disease, by providing an effective and well-tolerated vaccine with just one immunization, is a critical component of the global public health response," said Paul Stoffels, vice chairman of the Executive Committee and chief scientific officer, Johnson & Johnson. The ENSEMBLE study results include efficacy against newly emerging strains of coronavirus, including some highly infectious variants present in the United States, Latin America and South Africa, according to the company. Last month, the FDA authorized two Covid-19 vaccine for emergency use in the US, one developed by Moderna and the other developed by Pfizer in partnership with German company BioNTech. Unlike the vaccines from Moderna and Pfizer that require two shots given weeks apart, the Johnson & Johnson vaccine is given as a single shot. It also does not require ultracold storage. The US has recorded 25,909,336 Covid-19 cases with 436,541 deaths, according to the Johns Hopkins University. /IANS