Two more J&J trials underway to test vaccine in pregnant women and adolescents, and two-dose effect

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  • While the rollout of the J&J vaccine is happening in SA, it is being tested in two other studies
  • The first study will look at the vaccine's effect when administered as a two-dose regimen
  • The second study will assess the safety and efficacy of the vaccine on adolescents and pregnant women

About 52 000 healthcare workers have been vaccinated with the Johnson & Johnson Covid-19 vaccine as of Thursday, and scientists handling the rollout hope to reach a target of 80 000 by the weekend, said Professor Glenda Gray during a virtual webinar on Thursday evening.

South Africa is the first country to roll out this vaccine, after data from the phase 3 ENSEMBLE clinical trial showed that the single-shot offered strong protection against severe disease and hospitalisation. The trial involved over 40 000 participants, and was tested in SA where the new, highly infectious variant, 501Y.V2, has been dominating infections during the second wave.

J&J is also conducting two additional clinical trials. One is a phase 3 study enrolling 30 000 volunteers worldwide and will test how well the vaccine protects against Covid disease, caused by SARS-CoV-2, when two doses are administered.

The other is a phase 2A study that will assess the vaccine in adolescents and pregnant individuals, said Gray. The vaccine will be tested via both single shots and a two-dose regimen. This study will include 550 adults and 660 adolescents. Enrollment of adults is ongoing, but has not yet started for adolescents. 

Can pregnant women receive the J&J vaccine?

Gray explained that the vaccine has not yet been tested in pregnant women, but that the protocol will be amended and approval will be granted, hopefully by next week, to allow women who are more than 18 weeks pregnant to get the vaccine.

“But pregnant women would have to understand that this is not a registered product. And that they would have to look at the risk-benefit and [make a decision],” she said.

There is a rolling submission for the J&J vaccine to be licensed in South Africa, which will likely happen around April. It is currently being deployed in the country as part of a “phase 3B implementation study” which was designed together with the South African Health Products Regulatory Authority (Sahpra).

“A phase 3B study is where we know the vaccine is efficacious and we don’t have to do a randomised study with a placebo. We’re doing this [rollout] in a real-life situation to see how well it works,” Gray said.

J&J vaccine technology well-established

Gray added that the technology used for the J&J vaccine (adenovirus type 26, or Ad26) has previously been used in vaccines for Ebola, HIV, RSV and the Zika virus, and has been tested in pregnant individuals in those programmes with encouraging results.

“We know this Ad26 J&J vaccine platform very well. Because of the experience with this platform, it was very easy to add the immunogens for SARS-CoV-2; in this case, it was the spike protein,” Gray explained.

But if you know you’re pregnant, or are planning on falling pregnant, Gray advises you wait until 18 weeks of pregnancy to get the J&J vaccine. “It’s probably safe, but we need more data,” she said. 

How long will the J&J vaccine offer protection?

“These vaccines are like a year old so we’re still accumulating that data. And so we do suspect that they will be durable,” said Gray, but researchers will be assessing, over time, when the vaccine-induced antibodies start waning and if and when individuals might need a booster shot. 

Will the vaccine protect against transmission?

Unfortunately, none of the clinical trials to date have looked at transmission of the virus after vaccination, said Gray.

Instead, the clinical trials undertaken by all vaccine developers, including J&J, Oxford-AstraZeneca, Pfizer-BioNTech, and Moderna, studied whether the vaccines protect the individual against Covid-19 illness.

“When you design a transmission study, you design a different study. None of the vaccine studies have done a transmission study," she said.

To understand how well the vaccine works at preventing transmission of the virus, mass vaccinations would have to take place, and one could then infer based on that data, such as is the case in Israel. Either that or a transmission study would have to be designed.

Gray explained that this kind of study could be done at universities, where one university group is vaccinated and the other isn’t, and then compare the data. “It’s a complicated study but they are being designed at the moment,” she said.

READ | Coronavirus variants update: One has spread to over 90 countries, two on WHO watchlist

READ | SA scientists testing traditional medicine to fight Covid-19 – with promising early results

READ | EXPLAINER: How we know vaccines are safe and effective

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