AstraZeneca says the company's Covid-19 vaccine has only limited efficacy against a new strain of nCoV discovered in South Africa.

"In the small phase I / II trial, initial data showed the vaccine's limited effectiveness in preventing mild disease symptoms caused by the South African virus strain B.1.351," said an AstraZeneca spokesperson.

This study was conducted by Witwatersrand University and Oxford University and published in the Financial Times.

The three nCoV strains that are of most interest to scientists and public health experts are the new British, South African and Brazilian strains, as they appear to be able to spread faster than others.

The study by the two universities was conducted with more than 2,000 participants, but did not say any of them were hospitalized or died from the new variant of South Africa's nCoV strain whether vaccinated or not.

"We have not been able to determine the exact effect of the vaccine on serious illness or hospitalization, because most of the participants are healthy young people," added an AstraZeneca spokesman.

However, British pharmaceutical company AstraZeneca says it believes its vaccine can protect people from serious complications, as the antibody activity is comparable to the proven Covid-19 vaccines.

In addition, the AstraZeneca representative added that the company and Oxford University have begun modifying their vaccines to increase effectiveness with new strains and are rapidly evolving for availability this fall.