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A Johnson & Johnson COVID-19 vaccine at a vaccination center established at the Hilton Chicago O'Hare Airport Hotel in Chicago, Illinois. Image Credit: AFP

Geneva: The WHO's expert vaccine advisers said Wednesday they could recommend the Johnson and Johnson jab for use in countries where variants of the new coronavirus are circulating.

The vaccine, which can be used on people aged 18 and above, has proven effective "in the countries where there is a high spread of the variants", Alejandro Cravioto, the head of the World Health Organization's Strategic Advisory Group of Experts (SAGE) on Immunization, told reporters.

Johnson & Johnson’s long-awaited vaccine appears to protect against COVID-19 with just one shot - not as strong as some two-shot rivals but still potentially helpful for a world in dire need of more doses.

J&J said that in the US and seven other countries, the single-shot vaccine was 66% effective overall at preventing moderate to severe illness, and much more protective - 85% - against the most serious symptoms.

J&J’s shot uses a cold virus like a Trojan horse to carry the spike gene into the body, where cells make harmless copies of the protein to prime the immune system in case the real virus comes along.

AstraZeneca makes a similar cold virus vaccine that requires two doses. Both the AstraZeneca and J&J vaccines can be stored in a refrigerator, making them easier to ship and to use in developing countries than the frozen kind made by Pfizer and Moderna.