Johnson & Johnson says its single-shot COVID-19 vaccine shows strong promise against the Delta variant and other emerging strains.

In news that will come as a relief to more than 12 million Americans vaccinated with Johnson & Johnson, data showed that the durability of immune response for recipients of its vaccine lasted at least eight months, the healthcare company said on Thursday (local time).

As well as providing durable protection against the infection more broadly, Johnson & Johnson says its vaccine was 85 per cent effective and could also help prevent hospitalisation and death.

First identified in India, Delta is becoming the globally dominant variant of the coronavirus, according to the World Health Organisation.

“Current data for the eight months studied so far shows that the single-shot Johnson & Johnson COVID-19 vaccine generates a strong neutralising antibody response that does not wane; rather, we observe an improvement over time,” Mathai Mammen, head of research & development at J&J’s drugs business, said in the statement.

Recipients of the vaccine produced strong neutralizing antibodies against all variants including the Delta, the US-based company said.

The Delta variant contributed to a surge in COVID-19 cases in India that resulted in the highest daily death tally in the world, and also prompted the UK to delay its reopening by one month in June.

J&J has submitted data as a preprint to the website bioRxiv ahead of peer review.

Other vaccine makers including Pfizer-BioNTech, Moderna and AstraZeneca have previously said their COVID-19 vaccines are effective against the fast-spreading Delta.

-with agencies