New Covid vaccine found to be safe and effective - when will the UK get it? (PA) The latest review by US regulators of the single-shot Johnson & Johnson Covid-19 vaccine has found the jab to be safe. The UK has already odered 30 million doses of the jab will be seen as a more cost-effective vaccine as not only does it require less jabs, it can also be stored in refrigerator instead of a freezer. The vaccine’s effectiveness varied in different countries, with 72 per cent efficacy in the United States, 66 per cent in Latin America, and 57 per cent in South Africa - where a new variant has spread, according to the US Food and Drug Administation (FDA).