India has detected in four travellers from Africa the so-called South African novel coronavirus variant that has become a source of worry among scientists worldwide because of its potential to evade vaccines.

The South African variant known as B.1.351 has been detected in one returnee from Angola, one from Tanzania, and two from South Africa, health officials disclosed on Tuesday, but declined to specify their locations in India.

The B.1.351 variant that was first documented in South Africa in mid-December last year and has since spread to over 40 countries carries multiple mutations and appears to have increased transmissibility just like the B.1.1.7 variant first identified in the UK. But B.1.351 also has certain mutations that scientists believe could make some vaccines less effective against the variant.

All the travellers’ contacts have been tested and quarantined and the National Institute of Virology, Pune, is trying to isolate and culture the variant, said Balram Bhargava, director-general of the Indian Council of Medical Research.

The travellers had arrived in India during the third and fourth week of January, a health official said.

Bhargava said another variant that emerged in Brazil in January this year has also been detected in one returnee from that country. The NIV has isolated the Brazil variant and has begun experiments to assess the vaccine’s effectiveness against it, he said.

Studies have already found that the homegrown Covid-19 vaccine named Covaxin, jointly developed by Bharat Biotech and the ICMR, is effective against the UK variant which has so far been detected in 187 cases in India.“There is so far no evidence that either the UK or the South Africa variants have had any effect on the epidemic patterns in India — we don’t see any clustering, no unusual trends or reinfections,” a senior scientist associated with the sequencing effort told The Telegraph.

Scientists in labs across the world are trying to determine how well current Covid-19 vaccines will work against these emerging variants. Some studies have suggested that the B.1.351 variant is less effectively neutralised by antibodies from vaccinated people.

South Africa had earlier this month announced a plan to halt the rollout of the AstraZeneca-Oxford vaccine amid preliminary evidence indicating marked reduction in vaccine efficacy against mild and moderate disease caused by the B.1.351 variant.

However, given the small sample size in the South African study, the World Health Organisation has currently recommended that the AstraZeneca-Oxford vaccine should be used even if the variant is present in a country.