Covid-19 vaccines and the Delta variant: What we know

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  • Scientists are continuing to study how well the current Covid-19 vaccines work against the new Delta variant.
  • At this stage, data on most of the jabs are still very limited.
  • One analysis, however, showed that the Pfizer vaccine is protective against the new variant after both doses.

The highly infectious Delta SARS-CoV-2 variant caused a ferocious wave of infections in India and has now spread to more than 85 other countries, including South Africa, where it’s starting to dominate Covid-19 infections.

The variant, also known as B.1.617.2, is believed to be 60% more transmissible than the Alpha variant first detected in the UK. It is currently on the World Health Organization’s list of variants of concern (VOC) along with Alpha, Beta (first identified in SA), and Gamma (first identified in Brazil).

In his address to the nation on 27 June, President Cyril Ramaphosa announced that the country was in "the grip of a devastating" third wave of Covid cases, driven by the Delta variant, and that it might last longer than the previous two waves. The variant has already been found in Gauteng, KwaZulu-Natal, the Eastern Cape, the Free State, and the Western Cape. 

The Delta variant is, so far, the most transmissible form of the Covid-19 virus in the world, notes Bhekisisa. In other words, it is able to spread much more efficiently between people, compared to the other variants. There is also the concern that people with prior infection with the Beta variant could be susceptible to reinfection with Delta.

We take a look at what the data so far suggest about the effectiveness of the currently available vaccines against the Delta variant.


Findings from Public Health England analysis showed that the Pfizer vaccine was 33% effective against symptomatic infection from the Delta variant after the first shot of the two-dose series.

When people received their second shot, however, the efficacy was 88%, meaning that being fully vaccinated is likely to offer sufficient protection against the Delta variant.

The Pfizer-BioNTech vaccine is currently being administered six weeks apart in South Africa, after an initial plan to have a three-week gap between shots. However, there is great cause for concern with the country being under pressure from the third wave of infections, believed to be driven by Delta, Health24 reported

Johnson & Johnson (Janssen)

At this stage, the science is less clear on Johnson & Johnson’s one-dose jab and its protection against the Delta variant. The company said it was testing whether the immune response from its vaccine is capable of neutralising the troublesome variant in a laboratory setting, but no data are available as yet, according to Reuters.

Some experts estimate that it provides about 60% protection, perhaps extrapolating from the PHE study on a similar vaccine by Oxford-AstraZeneca, reports NBC Boston

Other experts are also considering following up the single jab with a booster shot of the Pfizer or Moderna mRNA-based vaccines, although there are no data published indicating the safety and effectiveness of mixing and matching these two jabs.

Dr John Beigel, an NIAID (National Institute of Allergy and Infectious Diseases) scientist told Reuters that if variant-driven infections and hospitalisations increase significantly, "then decisions might need to be made with an absence of data. But right now, I do think it's appropriate that they wait."

Sinopharm and CoronaVac 

Data on the protection of two Chinese Covid vaccines, namely Sinopharm (developed by the Beijing Institute of Biological Products) and CoronaVac (developed by the private Chinese company Sinovac) against the Delta variant are also currently limited.

In an interview with state media, Feng Zijian, researcher and former deputy director at the Chinese Center for Disease Control and Prevention (CDC) said that antibodies triggered by two Chinese Covid vaccines are less effective against the Delta variant compared with other variants, but that the shots still offer protection, a recent news piece by Reuters notes.

While Zijan didn’t name the two vaccines, he said they fell into the category of inactivated vaccines, which contain "killed" coronavirus that cannot replicate in human cells. Both Sinopharm and Sinovac’s vaccines use the inactivated approach, with the report adding that five out of seven Covid vaccines developed in China use this approach. 

Rise in infections in Indonesia despite vaccination with CoronaVac

According to a Reuters news article, 350 doctors and medical staff in Indonesia developed Covid infection despite being inoculated with CoronaVac. 

“Most of the workers were asymptomatic and self-isolated at home, said Badai Ismoyo, head of the health office in the district of Kudus in Central Java, but dozens were in hospital with high fevers and falling oxygen saturation levels.”

The region is seeing a surge in Covid infections, which health officials suspect is mainly due to the Delta variant, although Udayana University professor Gusti Ngurah Mahardika, Bali’s most senior virologist, told Al Jazeera that the new variant “is being used as a scapegoat because of the government’s incapacity to control the pandemic”.

The South African Health Products Regulatory Authority (Sahpra) announced last week that they received an application for the Sinopharm vaccine. The CoronaVac application is at an advanced stage, they said.

Sputnik V

According to a tweet on 15 June by the developers of the Russian Sputnik V Covid vaccine, their vaccine “is more efficient” against the Delta variant compared to other vaccines. They added that they submitted the data for publication to an international peer-reviewed journal. No data are publicly available yet to assess these statements.

Sahpra is currently reviewing the two-dose vaccine under a rolling review submission. This means that data are being continuously submitted for checking by the regulatory body as it becomes available. 

In May, Sahpra told Health24 that it had requested further information from the supplier of this vaccine.

*For more Covid-19 research, science and news, click here. You can also sign up for our Daily Dose newsletter here.

READ | Delta variant in SA: Why getting your second shot of the Pfizer vaccine is so important

READ | Covid-19 vaccines: CoronaVac application at advanced stage, Sputnik V still under review - Sahpra

READ | Sahpra’s Covid-19 vaccine approval process: ‘The safety of the public takes precedence’

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