Explainer: Will S. African strain render vaccines ineffective in India?

What is the South African strain?

In December, two announcements of mutations in the novel coronavirus were announced. Apart from the prominent mutation discovered in the UK, there was another one found in South Africa. Both were similar in the sense of having mutations over the spike protein of the virus through which the pathogen attaches to human cells. It was especially a cause of concern as most vaccines being developed are targeting the spike protein gene, alterations in which could render them less effective.

Are the vaccines less effective against the mutant variant?

Studies have shown that vaccines developed against the original strain are less effective against the mutant variants, particularly the one from South Africa. Initial studies were conducted only in the laboratory and did not involve human volunteers. They also focused on the UK strain.

Most vaccines showed they worked against the UK variant of the virus. However, efficacy studies conducted in South Africa showed that vaccines were less effective against the variant found there. Results from Moderna suggested its vaccine is still effective against the South African strain, though there may be some impact on the strength and duration of the protection. Efficacy trial results of Novavax and Johnson & Johnson also showed that their vaccines could protect against the strain, though the efficacy was significantly lower.

The biggest impact was seen on the AstraZeneca vaccine when a study of about 2,000 people supported by its co-developer University of Oxford showed that the vaccine offered “minimal protection" of only 10.4% efficacy against mild disease caused by the South African variant. This was sharply lower than the 53-90% efficacy observed against the original strain depending on the quantum of doses and interval between them. Considering the small sample size, the results, which are not peer-reviewed, are not reliable.

Following the Oxford-supported study, the South African government has halted the use of the vaccine supplied by Serum Institute of India. The country is switching to the vaccine developed by Johnson & Johnson. In January, J&J had said that a single dose was 57% efficacious against the South African variant.

What about Indian vaccines?

AstraZeneca’s vaccine is contract manufactured by Serum Institute under the brand Covishield, which is expected to be significantly less effective against the new variant. It is one of the two vaccines so far rolled out in India’s covid-19 immunization programme, the other being Bharat Biotech’s Covaxin.

Covaxin was shown to be effective against the UK variant of the virus in the pre-print of a laboratory study, but Bharat Biotech has not conducted a similar study against the South African variant.

Serum Institute will also contract manufacture Novavax’s protein subunit vaccine under the brand Covovax, and this vaccine has shown a 60% efficacy against the South African variant, which though lower than against the original variant is still higher than the 50% cutoff for overall efficacy.

Is this a cause of concern?

As only four cases have been found in India, this is not a major cause of worry. It may be a cause of concern if the spread of the South African variant is not contained in India. However, even then, it would depend on the progress of covid-19 vaccination and the choice of covid-19 vaccines that are available over time, especially those that are effective against the new strain.