Johnson & Johnson said on Friday that its single-dose vaccine was 66% effective in preventing COVID-19 in a large global trial against multiple variants.
In the trial of nearly 44,000 volunteers, the level of protection against moderate and severe COVID-19 varied from 72% in the United States, to 66% in Latin America and just 57% in South Africa, from where a worrying variant has spread.
The data showed that the vaccine’s effect on the South Africa variant was diminished compared to the unaltered virus, but infectious disease and public health experts said it can still help contain the virus spread and prevent deaths.
Midstage trial data from Novavax on Thursday also documented lower effectiveness in South Africa.
Rival shots from Pfizer/BioNTech and Moderna were both around 95% effective in preventing symptomatic illness in pivotal trials when given in two doses.
Those trials were conducted mainly in the United States and before the emergence of new variants. These mean that the world is racing against time and with limited supplies to vaccinate as many people as possible, and quickly, to prevent virus surges.
COVID-19 is rising in 37 countries and infections have surpassed 101 million globally.