A new South African study shows that a second Johnson & Johnson dose, administered 6-9 months after the initial single-dose vaccine provided 84% protection against hospitalization from the Omicron SARS-CoV2 variant – results that even outperformed those of an earlier South African study looking at effectiveness of the two-dose Pfizer regime in the face of Omicron.

The study, published in the medrxiv.org preprint server on Thursday,  measured the vaccine’s effectiveness in a group of some 227,000 health care workers, including 69,000 people who received the vaccine booster, between 8 November and 17 December – just as the Omicron variant was taking hold in the country.

The study found that vaccine efficiency against hospitalizations increased over time since the booster dose was administered from 63% in the first to weeks, to 85% post-boost.

“This data is important given the increased reliance on the Ad26.COV.2 [J&J] vaccine in Africa,” said the team of researchers, led by scientists at the South African Medical Research Council, the Desmond Tutu HIV Centre, and other prominent research centers.

Previous large-scale South African study on two Pfizer jabs yielded weaker results

The study contrasts with a 14 December report on Pfizer vaccine efficacy in the face of Omicron by one of South Africa’s largest insurance providers.

The study by Discovery Health,  found that a two-dose Pfizer-BioNTech vaccine provided 70% protection against severe COVID cases, requiring hospitalizations, but only 33% protection against COVID infection during the current Omicron wave. The study examined some 211,000 COVID-19 test results obtained between 15 November and 7 December, 41% of which were from adult members who had received two-doses of the Pfizer vaccine.

Although the U.S. Food and Drug Administration was one of the first regulatory agencies to authorize the Johnson & Johnson/Janssen COVID-19 vaccine in February 2021, and following that, a booster shot, the vaccine had fallen from favour more recently in the United States. And that was following warnings from the US Centers for Disease Control and Prevention about rare but life-threatening blood clots that could be linked to the vaccine.

The South African Medical Association in November also had protested the exclusive arrangements between Johnson & Johnson and the government which led to health workers having only one booster option – a second J&J jab – while the company ran research on the results.

Latest South African results – turn earlier assumptions on head

At the time, the South African Medical Association complained that the Pfizer jabs appeared to generate a more robust response – and should thus also be made available to highly exposed health workers.

Now, those assumptions may be turned on the head.

The J&J vaccine has been an anchor of the South African vaccine response from the beginning of vaccine rollouts – where the jab is also being produced in a collaboration with Aspen Pharmaceuticals for domestic use – as well as for the wider African market.

Along with stimulating a high degree of response with the first shot, the J&J vaccine can remain stable for up to three months at  2°C to 8°C, while the Pfizer and Moderna mRNA vaccines require cold chain storage at -28°C to 70°C.

The J&J vaccine uses a inactivated adenovirus  (cold virus) to deliver a genetic fragment of the SARS-CoV2 spike protein into the body, which in turn stimulates immune response.

In contrast, the Pfizer and Moderna vaccines deliver messenger RNA (mRNA) – a single strand genetic instruction making part of a SARS-CoV2 spike protein – into the body.  And that mRNA triggers and immune response.

Unexpectedly potent T Cell responses to Omicron Variant

In another a pre-print laboratory study published on 26 December, South African researchers also found that T-cells taken from people who received Johnson & Johnson vaccines recognized Omicron-infected cells almost as well as they recognized cells infected with other variants. That study is also significant as it suggests that even if antibody response to Omicron is not as robust in vaccinated individuals, the other critical factor in the body’s immune response remains more resilient.

“We found that 70-80% of the CD4 and CD8 T cell response to spike was maintained across study groups. Moreover, the magnitude of Omicron cross-reactive T cells was similar to that of the Beta and Delta variants, despite Omicron harbouring considerably more mutations,” wrote the authors, led by scientists at the University of Cape Town.

See here a video about how the four main categories of SARS-CoV2 actually work:

https://youtu.be/lFjIVIIcCvc

Image Credits: Johnson & Johnson, NBC News.